HP500EFI problem....

[kevnmcd]

I have an issue with one of my motors getting hot and was hoping one of you might be able to help. The starboard motor never moves off of 150* on the gauge. The port motor however sometimes will creep up to 175-190* and stay there. Sometimes it will come back down to 150 on its own other times I have to stop put it in neutral and bring the rpm's up a bit and it drops right back down to 150 but will eventually climb back up while under way. I have had a mechanic go through every possible thing at this point...drive, impellor, oil cooler, ps cooler, fuel cooler, new thermostat, circulating pump on motor, new sending unit, etc. Everything is clear and no blockages. We know it is getting enough flow as the exhaust risers aren't getting hot but somehow the motor is. It is also vapor locking on me which tells me it is getting hot but no vapor lock on the starboard one. There is no power loss in it, no water in the cylinders and plugs look good. We just can't figure out what the hell is going on. Anyone have any ideas?

 

[HALLETT BOY]

Has an impeller ever come apart ? have you ever sucked up any small rocks or grass ? I took my engine oil cooler off one time and picked small rocks and debris out of the small cooling passage holes , couldn't back flush , they were wedged in firmly ... took a length of welding rod and ran it through .

 

[Racey]

If you have eliminated the impellar/housing/blocked cooler/thermostat, my best guess is that sometimes the plastic tapered inserts that secure and seal the water inlet house inside the gimbal housing, the hose that connects the actual outdrive to the inner transom plate, those tapered inserts will break/collapse, and restrict actual water flow entering the cooling system. When they are new they are only about 3/4" inner diameter, but when they collapse they will restrict the flow down to about 3/8"-1/2", a huge difference.

The only way to check that is to pull the drive, and also pull the inner hose fitting on the transom plate (with the 2 bolts) and inspect each end.

 

[Havasu Hangin']

Hows the oil temp?

 

[kevnmcd]

Has an impeller ever come apart ? have you ever sucked up any small rocks or grass ? I took my engine oil cooler off one time and picked small rocks and debris out of the small cooling passage holes , couldn't back flush , they were wedged in firmly ... took a length of welding rod and ran it through .

Previous owner said he lost an impellor once on that motor but that was 200 hours ago and he said he never had a problem with it heating up. Also, as mentioned, we have gone through every cooler and removed every impellor blade, rock, pebble, blade of grass, etc. We even ran it for a few minutes with the thermostat housing removed to see if there was something in the block. Had flow coming out and no debri. Everything is clear with no obstructions that we can tell. Plenty of water coming out of the exhaust, also.

 

[kevnmcd]

If you have eliminated the impellar/housing/blocked cooler/thermostat, my best guess is that sometimes the plastic tapered inserts that secure and seal the water inlet house inside the gimbal housing, the hose that connects the actual outdrive to the inner transom plate, those tapered inserts will break/collapse, and restrict actual water flow entering the cooling system. When they are new they are only about 3/4" inner diameter, but when they collapse they will restrict the flow down to about 3/8"-1/2", a huge difference.

The only way to check that is to pull the drive, and also pull the inner hose fitting on the transom plate (with the 2 bolts) and inspect each end.

Mechanic said that he pulled the drive and checked everything and it is getting plenty of flow coming out the exhaust so I don't think that is it.

Hows the oil temp?

Don't have an oil temp gauge. Only oil pressure and that is fine.

 

[djunkie]

Have you tried a different prop? J/K Try a different temp gauge maybe.


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[Havasu Hangin']

Don't have an oil temp gauge. Only oil pressure and that is fine.

If your oil is getting hot in that motor, it would also cause those symptoms. Not saying that's it, but if you've tried everything (including swapping sending unit wires on the water temp gauges), I'd probably look at the oil cooler thermostat next.

 

[kevnmcd]

Have you tried a different prop? J/K Try a different temp gauge maybe.


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The temp was verified with the ECM as it thru a water temp code so I know the gauge is working correctly.

If your oil is getting hot in that motor, it would also cause those symptoms. Not saying that's it, but if you've tried everything (including swapping sending unit wires on the water temp gauges), I'd probably look at the oil cooler thermostat next.

There is a thermostat in the oil cooler? I wasn't aware of that. I will check with him and see if he as checked that. Thanks.

 

[Havasu Hangin']

There is a thermostat in the oil cooler? I wasn't aware of that. I will check with him and see if he as checked that. Thanks.

It helps the oil heat up faster. If it fails, the oil flow will be restricted to the cooler, and the oil will run hotter- much hotter under extended loads.

Not saying that's it, but oil temps are at least something to rule out.

 

[kevnmcd]

HH - It makes sense to me. As I said, I wasn't aware that they had one but now I do. I am going to have IR thermometer with me this weekend and will do some comparison readings between the two motors to see if the oil is getting hotter in one than the other. Thanks for the info.

 

[Meaney77]

Check your thermostat and housing

Had something similar happen on my HP 500 when I bought it from the previous owner it ran hot. I pulled EVERY line off and made sure there was no debris. Like Hallett Boy said, I checked the oil cooler and got some welding rod to un-lodge any small rocks that might be wedged. Still ran hot.... Took the boat to Lake Piru and pulled the drain plugs on the block and drove to flush any sand out that was in the block still ran hot. (Actually amazed me how much sand came out)

Finally after being totally frustrated I took the boat to Savage Marine when Steve owned it. They found that the thermostat and housing was put back together incorrectly. I changed the thermostat but put it back together exactly the way it came apart. (Not to be confused with putting the thermostat in backwards, that didn't happen). The previous owner/mechanic must have put it together wrong so I continued to put it together wrong also.

As soon as Savaged swapped it, the boat ran fine with no more cooling issues.

 

[rivermobster]

I had a "mechanic" replace the impeller in my boat couple summers ago, and it kept doing exactly what your discribing. I replaced everything as well.

I finally ordered the shop manual, took the water pump apart myself, and found it has been put back together incorrectly.

If you have a set of hand tools, it's not hard to do. The factory shop manual is worth every penny. :thumbsup

 

[Racey]

Mechanic said that he pulled the drive and checked everything and it is getting plenty of flow coming out the exhaust so I don't think that is it.



Don't have an oil temp gauge. Only oil pressure and that is fine.

You won't notice the waterflow difference running on the trailer, especially pressure feeding it off the hose, it only becomes restrictive at higher running speeds. It usually isn't the one on the drive end that collapses it is the one on the inner transom plate. I've seen it before. Just had one that did it in here about 3 weeks ago. Just a suggestion as your last resort.

Could also be the gauge taking a shit, you could always eliminate that by hooking the temp wires to the opposite motor and seeing what happens, also verifying with IR thermo.

 

[kevnmcd]

Check your thermostat and housing

Had something similar happen on my HP 500 when I bought it from the previous owner it ran hot. I pulled EVERY line off and made sure there was no debris. Like Hallett Boy said, I checked the oil cooler and got some welding rod to un-lodge any small rocks that might be wedged. Still ran hot.... Took the boat to Lake Piru and pulled the drain plugs on the block and drove to flush any sand out that was in the block still ran hot. (Actually amazed me how much sand came out)

Finally after being totally frustrated I took the boat to Savage Marine when Steve owned it. They found that the thermostat and housing was put back together incorrectly. I changed the thermostat but put it back together exactly the way it came apart. (Not to be confused with putting the thermostat in backwards, that didn't happen). The previous owner/mechanic must have put it together wrong so I continued to put it together wrong also.

As soon as Savaged swapped it, the boat ran fine with no more cooling issues.

We have had it apart a couple times now looking at that possibility. Would your motor run hot immediately and stay hot?

I had a "mechanic" replace the impeller in my boat couple summers ago, and it kept doing exactly what your discribing. I replaced everything as well.

I finally ordered the shop manual, took the water pump apart myself, and found it has been put back together incorrectly.

If you have a set of hand tools, it's not hard to do. The factory shop manual is worth every penny. :thumbsup

Replaced a few impellors myself and we have done that check already and everything is correct. Thanks.

You won't notice the waterflow difference running on the trailer, especially pressure feeding it off the hose, it only becomes restrictive at higher running speeds. It usually isn't the one on the drive end that collapses it is the one on the inner transom plate. I've seen it before. Just had one that did it in here about 3 weeks ago. Just a suggestion as your last resort.

Could also be the gauge taking a shit, you could always eliminate that by hooking the temp wires to the opposite motor and seeing what happens, also verifying with IR thermo.

We will take a look at the hose. Definately not the gauge dying as the computer also showed a high temp code and it uses a different sensor on the block so at least they are consistent.

 

[H2oracer]

Check your thermostat to see what temp it opens. I had two new 143 degree thermostats go bad in less than 10 hrs. One would only partialy open at 165 the other would start to open at 177. These are the brass high flow Robert Shaw design that are made in CHINA. I have done some research and a lot of car guys have had problems with the 180 degree version. Not the quality product it used to be when they were made in the USA.

 

[Meaney77]

We have had it apart a couple times now looking at that possibility. Would your motor run hot immediately and stay hot?

Yes, It would run hot after about 10 minutes of driving and the only way it would cool down would be to come to a complete stop with the motor idling.

You have 2 motors, I would pull the thermostat and housing apart on the good motor and just double check how it comes apart and put it back together the same way it comes apart. Unfortunately I'm not in front of my boat but if I remember, I think there is a spacer or something between the block and the neck and the thermostat has to go on the side closest to the block so that the spacer goes on top. Dont quote me but I think thats how it goes. At any rate check your other motor that is running fine. It was literally so stupid when they found out what was wrong but so frustrating for me to figure out.

 

[kevnmcd]

Check your thermostat to see what temp it opens. I had two new 143 degree thermostats go bad in less than 10 hrs. One would only partialy open at 165 the other would start to open at 177. These are the brass high flow Robert Shaw design that are made in CHINA. I have done some research and a lot of car guys have had problems with the 180 degree version. Not the quality product it used to be when they were made in the USA.

At first we thought it was the thermostat so we replaced it. Had a 160* in there so that is what we replaced it with. Still overheated so we pulled the other motor thermostat housing off to check what that had in it and it was a 140* so we put that in this one (140*) before last trip and still didn't fix it.

Yes, It would run hot after about 10 minutes of driving and the only way it would cool down would be to come to a complete stop with the motor idling.

You have 2 motors, I would pull the thermostat and housing apart on the good motor and just double check how it comes apart and put it back together the same way it comes apart. Unfortunately I'm not in front of my boat but if I remember, I think there is a spacer or something between the block and the neck and the thermostat has to go on the side closest to the block so that the spacer goes on top. Dont quote me but I think thats how it goes. At any rate check your other motor that is running fine. It was literally so stupid when they found out what was wrong but so frustrating for me to figure out.

As mentioned above we have pulled both housings off so I don't think that is it either. I know it is going to be something simple/stupid, we just have to figure out what it is.

 

[steamin rice]

The fun part of having twins.... I had one motor that would run about 10 degrees warmer than the other if the RPMs were above 3500 RPM - I checked the water pressure for both sides with my smartcraft monitors and found that the pressure on one side was lower than on the other side. Took the impeller apart and the housing was slightly scored. I replaced the housing and new impeller, now both sides have about the same water pressure and run the same temp.

This likely is not what you have, since you have already done the obvious checks.

One thing you can do to trouble shoot is to swap the water intake hoses from the drive to the engine (port engine gets water from starboard drive and vice versa) and see if the problem stays with the engine or with the drive. I never tried this, but know of someone who did to track down a cooling issue - He had a dead lizard stuck in one of his drives!

 

[kevnmcd]

The fun part of having twins.... I had one motor that would run about 10 degrees warmer than the other if the RPMs were above 3500 RPM - I checked the water pressure for both sides with my smartcraft monitors and found that the pressure on one side was lower than on the other side. Took the impeller apart and the housing was slightly scored. I replaced the housing and new impeller, now both sides have about the same water pressure and run the same temp.

This likely is not what you have, since you have already done the obvious checks.

One thing you can do to trouble shoot is to swap the water intake hoses from the drive to the engine (port engine gets water from starboard drive and vice versa) and see if the problem stays with the engine or with the drive. I never tried this, but know of someone who did to track down a cooling issue - He had a dead lizard stuck in one of his drives!

Don't think it is a impellor/housing issue as they both are new and it was happening before we swapped them out. We pulled the drive and checked all the water passages and they are clear so I don't think swapping the intake hoses would change anything but you never know.

 

[Outdrive1]

It only does it under way? When you stop and bring the rpms up its cools off.

I know you said he pulled the drive and checked everything. The hose that goes from the bell housing(bell housing on a boat is what the drive bolts to, and then bolts to the gimbal ring)to the transom is under water when you stop. It's out of the water when you're moving. If its leaking it will suck air when it's out of the water. It has the shitty plastic fitting that Racey mentioned that goes inside of it to hold it to the bell housing. since you've done everything else, I'd pull the drive and change it also.

Also if the drive itself has a restriction you could always try swapping drives and props to see if the problem follows the drive.

 

[kevnmcd]

I will answer these separately so they don't get missed.....

It only does it under way? When you stop and bring the rpms up its cools off.

It doesn't do it while idleing and at low rpms while under way. Anything over about 2800-3000 rpms and it will start to climb but not always steadily. I can have it go up sit at about 175* and then without doing anything it will drop back down. I have even seen it go down if I give it more throttle but typically I have to pull it back on the sticks to 2500 or less and sometimes I have to bring it back to neutral and give it a little gas. It will always come back to 150 in neutral with a little gas.

I know you said he pulled the drive and checked everything. The hose that goes from the bell housing(bell housing on a boat is what the drive bolts to, and then bolts to the gimbal ring)to the transom is under water when you stop. It's out of the water when you're moving. If its leaking it will suck air when it's out of the water. It has the shitty plastic fitting that Racey mentioned that goes inside of it to hold it to the bell housing. since you've done everything else, I'd pull the drive and change it also.

I hear you however with my old eliminator I had a crack in my impellor housing once and it was sucking air. The way I found that out is as the air pockets moved through the motor when they would hit the temp sending unit it would peg the needle immediately and then it would bounce right back to normal when the water hit it (very fast up/down). This one is climbing slowly and very stable needle which is telling me that there isn't any air (or at least not much) in the system.

Also if the drive itself has a restriction you could always try swapping drives and props to see if the problem follows the drive.

I really don't think it is a starvation of water at least I don't think so. I have put my hands on all 4 exhaust risers during a heat up and all 4 feel identical in temp at least to the bare hand. If there was a starvation of water, I would think that one set would be hotter than the other. Would you agree?

 

[Outdrive1]

Head issues can cause overheating also. Exhaust in the coolant, under load will cause an overheat issue. You'd probably see some signs on the plugs, or have a misfire at idle though.

You mentioned vapor lock, not hydro locking? Does it ever not turn over?

 

[kevnmcd]

Head issues can cause overheating also. Exhaust in the coolant, under load will cause an overheat issue. You'd probably see some signs on the plugs, or have a misfire at idle though.

You mentioned vapor lock, not hydro locking? Does it ever not turn over?

Plugs and cylinders are dry and don't show any signs of water. It always turns over. On the hot days (100*+) if I let it sit after running to a spot for a while it will start and then die. I have tried leaving the hatch open but without moving it still has too much heat back there. If I have problems like this I just leave the hatch open idle with the other motor and in about 5-10 minutes it will fire right up and run fine. I have done a little internet searching on this year motor (1999) and it appears that vapor locking was a known problem with them and was fixed in 2001, I believe. I don't have this issue with the other motor because it never gets over 150* and they say that vapor lock will happen at around 175*. I am not sure if the 2 problems are related but it makes sense especially since I have no issue on the other motor and it always starts just fine.

 

[kevnmcd]

A little update....I had an IF thermometer with me this weekend. After having the temp go up on the one motor, opened the hatch and took some temp readings. The only place I could find a difference in temp between the 2 motors was the head temp. The hot motor was about 12* hotter than the other one.

Does anyone know if a electric fuel pump can just lose pressure or are they a worky/no worky kind of deal? Wondering if the fuel pump is just not putting out enough pressure and leaning that motor out some thus creating more heat? It is definately not an impellor problem as it is getting plenty of flow.

 

[2FORCEFULL]

what happens is exhaust gets pumped in to the simese cylinder and leans it out...

check compression on #5 and #7... every hp500 I've had has blown a head gasket!!! the head bolts are too long and the they have blind holes...

some people put washers under the bolts... you should do a valve job on those motors... you need to replace the lifters and rockers....plus you wanna get those heads off before they suck a valve... then it's a night mare...that and when the lifters and rockers start spitting needle bearings,...

 

[Flyinbowtie]

I don't know what kind of fuel pumps you are running but the head being the only location you can find a temp difference with the IR thermometer makes me think a lean condition may be one potential source of the problem....I'd be checking the fuel pump, and the lines and make sure you are not sucking air someplace...which will cause the lean out and mimic vapor lock.

 

[2FORCEFULL]

Head issues can cause overheating also. Exhaust in the coolant, under load will cause an overheat issue. You'd probably see some signs on the plugs, or have a misfire at idle though.

You mentioned vapor lock, not hydro locking? Does it ever not turn over?

good post paul'''...most of the time it blows the gasket between the cylinders because the torqe on the head bolts

 

[2FORCEFULL]

I would not run those motors again with out doing a leak down...but then I'm always looking for trouble

 

[Outdrive1]

good post paul'''...most of the time it blows the gasket between the cylinders because the torqe on the head bolts

It's common for those motors to have head issues. It is what it is. They're great motors otherwise. 200plus hours or so and they need some attention.

 

[Riverbound]

It's common for those motors to have head issues. It is what it is. They're great motors otherwise. 200plus hours or so and they need some attention.

Mine has 240 ish hrs on it. Runs fine. But I know we are looking at some work down the road.

 

[Anarchy Powerboats]

Mechanic said that he pulled the drive and checked everything and it is getting plenty of flow coming out the exhaust so I don't think that is it.



Don't have an oil temp gauge. Only oil pressure and that is fine.

But did he back flush? "plenty" and factory spec may be different.

 

[2FORCEFULL]

Mine has 240 ish hrs on it. Runs fine. But I know we are looking at some work down the road.

my lifters are wore out , 238 hrs...

do a compression check on 5 & 7.. thats where it always starts

#7 runs lean on that motor...

 

[kevnmcd]

what happens is exhaust gets pumped in to the simese cylinder and leans it out...

check compression on #5 and #7... every hp500 I've had has blown a head gasket!!! the head bolts are too long and the they have blind holes...

some people put washers under the bolts... you should do a valve job on those motors... you need to replace the lifters and rockers....plus you wanna get those heads off before they suck a valve... then it's a night mare...that and when the lifters and rockers start spitting needle bearings,...

I had heard a lot of talk about this. When yours did this did you get any water in the cylinders or was it only between the cylinders?

I don't know what kind of fuel pumps you are running but the head being the only location you can find a temp difference with the IR thermometer makes me think a lean condition may be one potential source of the problem....I'd be checking the fuel pump, and the lines and make sure you are not sucking air someplace...which will cause the lean out and mimic vapor lock.

I hear you on the sucking air but it only happens after a long run on a hot day and letting it sit for an hour or so. Not that it couldn't be that though.

 

[kevnmcd]

But did he back flush? "plenty" and factory spec may be different.

Back flush and pull every cooler out and check for debri.

 

[2FORCEFULL]

my schiada ran fine till we had to tow it

 

[2FORCEFULL]

I had heard a lot of talk about this. When yours did this did you get any water in the cylinders or was it only between the cylinders?



I hear you on the sucking air but it only happens after a long run on a hot day and letting it sit for an hour or so. Not that it couldn't be that though.

first it was just between the cylinders..then it blew the rest of the gasket and let water into the manifold area


do youself a favor and do a compression check...and get them lifters out..

 

[kevnmcd]

do youself a favor and do a compression check...and get them lifters out..

Compression check coming up and that motor has had all the lifters replaced already about 100 hours ago.

 

[Kleptow]

mercury had an advisory on water flow on the HP 500 motor i would think if they wanted brand new packages checked then it's something id do at all major services intervals.

 

[kevnmcd]

mercury had an advisory on water flow on the HP 500 motor i would think if they wanted brand new packages checked then it's something id do at all major services intervals.

Have a copy of that advisory or know where I could find a copy to look over?

 

[28Eliminator]

A lot of the issues with the Carbureted HP500 were fixed with the 500EFI Motor. Both motors have basically the same internal parts, with the exception of the Cam. Same GM HO block, same 088 CI heads.

The big difference between the 2 of course being that the 500 EFI is fuel injected. It's my understanding that the Cam change in the EFI reduced the Spring wear problems that the HP motor had. The issue of the #7 running lean has always been a problem for BBC's due to the water flow through the heads causing higher CC temps, but the Dart Intake used on the HP motors compounded the problem making it worse.

 

[kevnmcd]

Went out this morning with my mechanic and a whole bunch of testing goodies and here is what we found.

- Fuel Pressure is good (38-42 psi)
- Compression is good
- Plenty of water flow at the tstat housing coming from the raw water impellor so no blockages in the oil/fuel/ps coolers
- Put a pressure gauge on the block down below the exhaust risers and only got 5 psi MAX at 3200-3800 rpms - figured this was low so moved the pressure gauge to the other motor to check what it had and got +/- 13 psi at the same rpm's

So the question is....why am I not getting water flow thru the block? We have had the circulating pump (pump on front of motor like in a truck/car) off and pulled apart and the impellor in there is turning. We are thinking that maybe the impellor fins are damaged or the tolerances are out so it is not pushing the water thru the motor....is that possible? What do you guys think? Any thoughts?

 

[mjc]

Have you checked block for sand?

 

[djunkie]

Went out this morning with my mechanic and a whole bunch of testing goodies and here is what we found.

- Fuel Pressure is good (38-42 psi)
- Compression is good
- Plenty of water flow at the tstat housing coming from the raw water impellor so no blockages in the oil/fuel/ps coolers
- Put a pressure gauge on the block down below the exhaust risers and only got 5 psi MAX at 3200-3800 rpms - figured this was low so moved the pressure gauge to the other motor to check what it had and got +/- 13 psi at the same rpm's

So the question is....why am I not getting water flow thru the block? We have had the circulating pump (pump on front of motor like in a truck/car) off and pulled apart and the impellor in there is turning. We are thinking that maybe the impellor fins are damaged or the tolerances are out so it is not pushing the water thru the motor....is that possible? What do you guys think? Any thoughts?

Could have sand in the block too.


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[Havasu Hangin']

Went out this morning with my mechanic and a whole bunch of testing goodies and here is what we found.

- Fuel Pressure is good (38-42 psi)
- Compression is good
- Plenty of water flow at the tstat housing coming from the raw water impellor so no blockages in the oil/fuel/ps coolers
- Put a pressure gauge on the block down below the exhaust risers and only got 5 psi MAX at 3200-3800 rpms - figured this was low so moved the pressure gauge to the other motor to check what it had and got +/- 13 psi at the same rpm's

So the question is....why am I not getting water flow thru the block? We have had the circulating pump (pump on front of motor like in a truck/car) off and pulled apart and the impellor in there is turning. We are thinking that maybe the impellor fins are damaged or the tolerances are out so it is not pushing the water thru the motor....is that possible? What do you guys think? Any thoughts?

Yes, pumps can have tolerance issues. Especially in Havasu, running sand through them can groove the backing plate. Every time I change my impellers, I make sure the backing plate is machined flat.

 

[mentalmatt]

Hey guys,

I know this sounds crazy, but is there any way you can pull the impellor from both units and measure them side by side? The reason I ask is recently I had my impellor changed at Nordic boats and worked with Bart the service manager over there. The first time I took my boat out after the impellor change, my boat was over-heating, so I took it back to Nordic. He said I need to rev the RPM's to about 2k when I put in the water to make sure I'm getting enough water in to properly cool it. Ok great, I do that and everything seems fine.

Fast-forward to 2 weeks ago, I call Nordic for another reason and speak to Bart again. He remembers me and asks if I'm still having the cooling issue with the impellor and I said yes, I still have to rev the RPM's to get it to cool properly.

That's when he told me that they found the issue because it's happening to a few other clients they recently changed the impellor on. He said he took an old impellor and one of the new ones from Mercury and noticed that Mercury actually changed the new impellors and they are like 0.3 smaller from the old ones. He said he has notified Mercury of the issue and they are working on fixing it, but they haven't released a new impellor yet to fix it.

My boat in Havasu and on hot days it hovers around 175 - 180... I usually don't see it drop below that. As well, if the boat has been sitting and I don't rev the RPM's up, the motor will start over-heating. I have to turn it off, turn it on, rev the RPM's and then the temp will immediately drop.

Bart at Nordic says this is the impellor change that is a different size than the old Mercury ones. He said once Mercury fixes this, I need to get a new impellor in there to fix the problem for good.

I know it sounds out there, but it might make sense for you to pull both impellors and measure them to make sure they are identical and you're not dealing with the same issue I am. He said because the impellor is slightly smaller that it's picking up water differently.

Now of course, I don't know if any of this is true or not because I have not verified it myself, but Bart strikes me as a good guy and so I'm taking his word on this one. Let me know what you think.

 

[kevnmcd]

Have you checked block for sand?

yes and no. When we took the plug out on the lower part of the block the water came out clear and clean with no sand.

Could have sand in the block too.

See above response.

Yes, pumps can have tolerance issues. Especially in Havasu, running sand through them can groove the backing plate. Every time I change my impellers, I make sure the backing plate is machined flat.

Not talking about the raw water impellor. Took the hose off at the thermostat housing coming from the impellor and getting plenty of flow. Like you, everytime I change the impellors I do the housing as well including the backing plate. I was talking about the circulating pump on the front of the block.

Hey guys,

I know this sounds crazy, but is there any way you can pull the impellor from both units and measure them side by side? The reason I ask is recently I had my impellor changed at Nordic boats and worked with Bart the service manager over there. The first time I took my boat out after the impellor change, my boat was over-heating, so I took it back to Nordic. He said I need to rev the RPM's to about 2k when I put in the water to make sure I'm getting enough water in to properly cool it. Ok great, I do that and everything seems fine.

Fast-forward to 2 weeks ago, I call Nordic for another reason and speak to Bart again. He remembers me and asks if I'm still having the cooling issue with the impellor and I said yes, I still have to rev the RPM's to get it to cool properly.

That's when he told me that they found the issue because it's happening to a few other clients they recently changed the impellor on. He said he took an old impellor and one of the new ones from Mercury and noticed that Mercury actually changed the new impellors and they are like 0.3 smaller from the old ones. He said he has notified Mercury of the issue and they are working on fixing it, but they haven't released a new impellor yet to fix it.

My boat in Havasu and on hot days it hovers around 175 - 180... I usually don't see it drop below that. As well, if the boat has been sitting and I don't rev the RPM's up, the motor will start over-heating. I have to turn it off, turn it on, rev the RPM's and then the temp will immediately drop.

Bart at Nordic says this is the impellor change that is a different size than the old Mercury ones. He said once Mercury fixes this, I need to get a new impellor in there to fix the problem for good.

I know it sounds out there, but it might make sense for you to pull both impellors and measure them to make sure they are identical and you're not dealing with the same issue I am. He said because the impellor is slightly smaller that it's picking up water differently.

Now of course, I don't know if any of this is true or not because I have not verified it myself, but Bart strikes me as a good guy and so I'm taking his word on this one. Let me know what you think.

I haven't heard this about the impellor sizes but this is the second impellor we have put in this year and that is not the problem as we are getting plenty of flow from that pump.

 

[kevnmcd]

Another update.....took the circulating pump off the front of the block and the thermostat housing and flushed the block reverse of the normal flow direction. Seems we are getting more water out of one side than the other leading us to believe that there is some type of obstruction in one side of the block. Not sure what it could be yet but we are narrowing it down.

 

[CampbellCarl]

Perhaps pieces of the raw water pump impeller from previous owners misuse is floating around and blocking circulation.

CC

 

[djunkie]

Of course there's always that "nature of the beast" deal. That motor may just run hotter.


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