Carburetor tuning high elevation

[Lumpy]

He'll, that thing is piglosi rich....

All say!

Could be from before with the stuck needle and seat?? These plugs have a season on them. Boat is running TITS, idle is a tad low but fires up like it’s EFI

Lets get a little scientific here shall we? One thing at a time. For starters your pic means nothing. Ya got old plugs semi recovered from a stuck bowl valve so your plug reading is shit. Ya wanna run at a higher altitude but you have nothing to go on for starters. Motor ran good till the carb went fugazi. Rebuild carb without changing jets or settings and run with NEW plugs properly gapped at the original altitude before climbing the hill. Hopefully the timing hasn’t been changed from its original setting when the motor ran right. Timing doesn’t know altitude…air fuel mixture does…don't fuck with it if it works. Dial in the rebuilt carb in Parker with new plugs and run some piss outa her…pull a plug. When all is good do the same at your new altitude and pull a plug…….THAT WILL BE YOUR READING AT ALTITUDE. Then you can make SMALL adjustments to dial her in at your new altitude. Sounds like rocket science but its not…one thing at a time and rule out the issues. Holley as a lot of info on line to help and if push comes to shove you can call them for advice.

 

[Lumpy]

Not looking forward to the power loss, but my wife is pregnant and due in July, I have a 2.5 year old, so that little bit shouldn’t be a problem cause I will only be cruising for the next few years

Missed that! Congratulation’s! Thats Awesome! Family is everything.

 

[coolchange]

All say!



Lets get a little scientific here shall we? One thing at a time. For starters your pic means nothing. Ya got old plugs semi recovered from a stuck bowl valve so your plug reading is shit. Ya wanna run at a higher altitude but you have nothing to go on for starters. Motor ran good till the carb went fugazi. Rebuild carb without changing jets or settings and run with NEW plugs properly gapped at the original altitude before climbing the hill. Hopefully the timing hasn’t been changed from its original setting when the motor ran right. Timing doesn’t know altitude…air fuel mixture does…don't fuck with it if it works. Dial in the rebuilt carb in Parker with new plugs and run some piss outa her…pull a plug. When all is good do the same at your new altitude and pull a plug…….THAT WILL BE YOUR READING AT ALTITUDE. Then you can make SMALL adjustments to dial her in at your new altitude. Sounds like rocket science but its not…one thing at a time and rule out the issues. Holley as a lot of info on line to help and if push comes to shove you can call them for advice.

His question was. “It runs great at Parker. How much should I lean on it to go to 5000’” The baseline set up is already established.

 

[Lumpy]

His question was. “It runs great at Parker. How much should I lean on it to go to 5000’” The baseline set up is already established.

Agreed but that plug reading he showed was super fat because the carb needed a rebuild….it was dumping fuel down its throat. My point was to get it running normal first…it may run fine the way it is at higher altitude.

 

[Croz]

Got the boat on the water twice this weekend. First was Topaz lake, with an elevation of 5010’. I was 1 of 4 boats, the other 3 were fishing boats so I’m sure I wasn’t a crowd favorite lol. Boat fired up still running rich, it cleared itself out a bit and I got it to a plane, it was instant I knew it wasn’t right. I swapped primary and secondary jets 4 times before it finally ran right. It ran good the rest of the day, just a little rich, but I barely got to high speeds. The next day we towed it to Lake Lohanton, which sits at 4100’. The boat ran awesome all day, never had a misfire, pop, loss of power, nothin. It was a very successful and fun day on the lake. Very similar to a Parker and havasu vibe as well which made it familiar feeling. Shout out to Battle Born Hot Boats for meeting up with me and giving me the run down of the lake. This will be our primary lake with out a doubt. Hoping for good weather this weekend and we will be back. If anyone lives in northern NV on this forum looking for something that isn’t a giant PITA like Tahoe, I highly recommend Lahontan.

Now to address the prop slip…currently running a bravo 26p 4 blade and it does not hop on a plane like it used to, and there’s definitely some slip at higher speeds, but nothing that will ruin the day. I wish everyone a safe boating season and thank you for your information and knowledge.

 

[Bigbore500r]

Got the boat on the water twice this weekend. First was Topaz lake, with an elevation of 5010’. I was 1 of 4 boats, the other 3 were fishing boats so I’m sure I wasn’t a crowd favorite lol. Boat fired up still running rich, it cleared itself out a bit and I got it to a plane, it was instant I knew it wasn’t right. I swapped primary and secondary jets 4 times before it finally ran right. It ran good the rest of the day, just a little rich, but I barely got to high speeds. The next day we towed it to Lake Lohanton, which sits at 4100’. The boat ran awesome all day, never had a misfire, pop, loss of power, nothin. It was a very successful and fun day on the lake. Very similar to a Parker and havasu vibe as well which made it familiar feeling. Shout out to Battle Born Hot Boats for meeting up with me and giving me the run down of the lake. This will be our primary lake with out a doubt. Hoping for good weather this weekend and we will be back. If anyone lives in northern NV on this forum looking for something that isn’t a giant PITA like Tahoe, I highly recommend Lahontan. View attachment 1505770
Now to address the prop slip…currently running a bravo 26p 4 blade and it does not hop on a plane like it used to, and there’s definitely some slip at higher speeds, but nothing that will ruin the day. I wish everyone a safe boating season and thank you for your information and knowledge.

Sounds like you worked your way down till it ran good, which is the way to do it.
Did you throw fresh plugs in it and then check them after running it? that will tell you if there's more left on the table by leaning it out further, and also to confirm it's at a "safe" AFR the way you have it jetted now.

 

[River Dirt 2]

Got the boat on the water twice this weekend. First was Topaz lake, with an elevation of 5010’. I was 1 of 4 boats, the other 3 were fishing boats so I’m sure I wasn’t a crowd favorite lol. Boat fired up still running rich, it cleared itself out a bit and I got it to a plane, it was instant I knew it wasn’t right. I swapped primary and secondary jets 4 times before it finally ran right. It ran good the rest of the day, just a little rich, but I barely got to high speeds. The next day we towed it to Lake Lohanton, which sits at 4100’. The boat ran awesome all day, never had a misfire, pop, loss of power, nothin. It was a very successful and fun day on the lake. Very similar to a Parker and havasu vibe as well which made it familiar feeling. Shout out to Battle Born Hot Boats for meeting up with me and giving me the run down of the lake. This will be our primary lake with out a doubt. Hoping for good weather this weekend and we will be back. If anyone lives in northern NV on this forum looking for something that isn’t a giant PITA like Tahoe, I highly recommend Lahontan. View attachment 1505770
Now to address the prop slip…currently running a bravo 26p 4 blade and it does not hop on a plane like it used to, and there’s definitely some slip at higher speeds, but nothing that will ruin the day. I wish everyone a safe boating season and thank you for your information and knowledge.

I’d try a 25 or even 23 Mercury Rev 4 at altitude. They work good on the straight bottom boats Like the 210 and 240

 

[Croz]

Sounds like you worked your way down till it ran good, which is the way to do it.
Did you throw fresh plugs in it and then check them after running it? that will tell you if there's more left on the table by leaning it out further, and also to confirm it's at a "safe" AFR the way you have it jetted now.

That is next on the list to get the proper reading. I have a feeling it’s still a little fat, but I bought plugs Incase I fouled one on Saturday. Thankfully no fouls, so I’ll throw those in this week, and check it out after. I’ll post a pic of the new plug and see what yall think as well. I did put 57 gallons of some good non ethanol fuel, I have a feeling that helped a lot lol

 

[Orange Juice]

View attachment 1504541

Clean, inspect for damage, regap, and run them, if you're running 87-octane.

 

[Croz]

Clean, inspect for damage, regap, and run them, if you're running 87-octane.

Non ethanol 87 from maverik

 

[Croz]

I’d try a 25 or even 23 Mercury Rev 4 at altitude. They work good on the straight bottom boats Like the 210 and 240

I’ll start looking around for one of these, thanks!

 

[NicPaus]

I’ll start looking around for one of these, thanks!

Look for a rev 23. The 25 will be to much prop if you are not pulling a 26 easily.

A 24 Bravo 1 will be easier to find.

I had a rev 25 and It was to much prop. I also had a stock 26 bravo 1 that was a little to much .

I have a 24 bravo 1 and a rev 23. The rev 23 takes a little more to turn it. I can hit rev limiter with both. The 25 I could not.

 

[Lumpy]

Got the boat on the water twice this weekend. First was Topaz lake, with an elevation of 5010’. I was 1 of 4 boats, the other 3 were fishing boats so I’m sure I wasn’t a crowd favorite lol. Boat fired up still running rich, it cleared itself out a bit and I got it to a plane, it was instant I knew it wasn’t right. I swapped primary and secondary jets 4 times before it finally ran right. It ran good the rest of the day, just a little rich, but I barely got to high speeds. The next day we towed it to Lake Lohanton, which sits at 4100’. The boat ran awesome all day, never had a misfire, pop, loss of power, nothin. It was a very successful and fun day on the lake. Very similar to a Parker and havasu vibe as well which made it familiar feeling. Shout out to Battle Born Hot Boats for meeting up with me and giving me the run down of the lake. This will be our primary lake with out a doubt. Hoping for good weather this weekend and we will be back. If anyone lives in northern NV on this forum looking for something that isn’t a giant PITA like Tahoe, I highly recommend Lahontan. View attachment 1505770
Now to address the prop slip…currently running a bravo 26p 4 blade and it does not hop on a plane like it used to, and there’s definitely some slip at higher speeds, but nothing that will ruin the day. I wish everyone a safe boating season and thank you for your information and knowledge.

Nice!!!! Thats how ya do it!! Glad ya got it worked out…well done sir!

 

[Croz]

Ok, new plugs, let it run for about 10 mins. Still looks fat

 

[Lumpy]

View attachment 1507522 Ok, new plugs, let it run for about 10 mins. Still looks fat

Yup…but you're getting close. I’d try two more sizes down…make sure you take a plug reading at operating temp.

 

[rivermobster]

View attachment 1507522 Ok, new plugs, let it run for about 10 mins. Still looks fat

Accurate Plug reads have to be done under Very specific circumstances.

This is a good article on how it actually should be performed and evaluated.

But of course, ignition timing should be set Properly first.

https://www.hotrod.com/how-to/spark-plug-reading-101-dont-leave-hp-table

 

[Orange Juice]

View attachment 1507522 Ok, new plugs, let it run for about 10 mins. Still looks fat

Did you check the gap on the plugs before installing? Whats the gap setting?
Also, if the coil is going bad, it wont create enough spark to burn all the fuel efficiently. I'd try another coil.

 

[DaveH]

View attachment 1507522 Ok, new plugs, let it run for about 10 mins. Still looks fat

WAYYYYYYYYY fat.

and i would ditch the iridium style plugs and go to traditional plugs.

 

[Bigbore500r]

WAYYYYYYYYY fat.

and i would ditch the iridium style plugs and go to traditional plugs.

Definetly. Needs some fresh NGK's and take a plug read from a single WOT run only, with no idle time on the plugs before or after the WOT run. NGK's are the easiest to read the timing mark on the strap. If the plug read isn't done directly after a WOT run on fresh plugs, they could be rich from idling which has very little to do with main jetting.

 

[Croz]

Definetly. Needs some fresh NGK's and take a plug read from a single WOT run only, with no idle time on the plugs before or after the WOT run. NGK's are the easiest to read the timing mark on the strap. If the plug read isn't done directly after a WOT run on fresh plugs, they could be rich from idling which has very little to do with main jetting.

Well damn that makes me rethink everything. These are/ were fresh NGKs that only have 10-15 mins of run time. it was mainly at an idle, which was high, and when I adjusted the 4 idle screws I did not notice much of a change at all. Was gonna downsize jets again this week and see if it would bring down the idle a bit and not run so rich. There’s a small amount of soot build up on the transom so I know it isn’t burning efficiently as it should

 

[Bigbore500r]

Well damn that makes me rethink everything. These are/ were fresh NGKs that only have 10-15 mins of run time. it was mainly at an idle, which was high, and when I adjusted the 4 idle screws I did not notice much of a change at all. Was gonna downsize jets again this week and see if it would bring down the idle a bit and not run so rich. There’s a small amount of soot build up on the transom so I know it isn’t burning efficiently as it should

That's good to know. It may in fact still be rich at WOT, but before you go crazy leaning it out further you definately should do a plug check without idling the motor much at all before (as little as possible), and definately not after the WOT run. Make the run, come off plane and shut it down ASAP, and pull a few plugs right there on the spot. That will give you an accurate reading on main jetting before the plugs can get sooted up from a fat idle.

Regarding idle mixture -
It really isn't controlled much at all by the main jets. It's controlled by a few things - The size of the IFR (idle feed restrictor) in the metering block, the size of the air bleed's in the main carb body. It is also indirectly affected by the float level (lowering the float a bunch can lean it out, at the expense of not having enough fuel when under load) and how much of the transfer slot is exposed on the carb baseplate, for the primary and secondary butterflies. If you don't have enough timing in the motor at idle, a common error is to compensate by over-adjusting the idle speed using the idle set screw on the carb to get the desired idle RPM. In doing this, the transfer slot in the primary throttle bore becomes "over exposed" by the butterfly that is cracked open too far, causing it to pull vacuum thru the carb's enrichment circuit and start adding fuel at idle when you don't wan't it to. That's why everyone says "set your timing first" before tearing into a carb to cure rich idle. Another common issue is that aftermarket Holley's (especially the HP series / race series carbs) have way too large of an IFR passage in the metering blocks to ever get a clean idle. That's a whole other conversation in itself, there's a few ways to take care of that issue if timing and mixture screws can't clean it up.

Sorry if i'm over explaining, but alot of this info is pretty eye opening if you've never dived in to fixing carb issues. 98% of people dont understand what actually controls idle mixture, and end up saying "it needs a smaller carb" or tossing a different carb on it when it just needs the Idle Feed Restrictors reduced by .004" to fix a rich idle!

 

[DaveH]

do yourself a favor and buy a wide band 02 setup. will take much of the guess work out of it. The soot on the transom is a sign of an overly rich mixture, but if the ignition is retarded this will also cover the transom.

 

[Lumpy]

That's good to know. It may in fact still be rich at WOT, but before you go crazy leaning it out further you definately should do a plug check without idling the motor much at all before (as little as possible), and definately not after the WOT run. Make the run, come off plane and shut it down ASAP, and pull a few plugs right there on the spot. That will give you an accurate reading on main jetting before the plugs can get sooted up from a fat idle.

Regarding idle mixture -
It really isn't controlled much at all by the main jets. It's controlled by a few things - The size of the IFR (idle feed restrictor) in the metering block, the size of the air bleed's in the main carb body. It is also indirectly affected by the float level (lowering the float a bunch can lean it out, at the expense of not having enough fuel when under load) and how much of the transfer slot is exposed on the carb baseplate, for the primary and secondary butterflies. If you don't have enough timing in the motor at idle, a common error is to compensate by over-adjusting the idle speed using the idle set screw on the carb to get the desired idle RPM. In doing this, the transfer slot in the primary throttle bore becomes "over exposed" by the butterfly that is cracked open too far, causing it to pull vacuum thru the carb's enrichment circuit and start adding fuel at idle when you don't wan't it to. That's why everyone says "set your timing first" before tearing into a carb to cure rich idle. Another common issue is that aftermarket Holley's (especially the HP series / race series carbs) have way too large of an IFR passage in the metering blocks to ever get a clean idle. That's a whole other conversation in itself, there's a few ways to take care of that issue if timing and mixture screws can't clean it up.

Sorry if i'm over explaining, but alot of this info is pretty eye opening if you've never dived in to fixing carb issues. 98% of people dont understand what actually controls idle mixture, and end up saying "it needs a smaller carb" or tossing a different carb on it when it just needs the Idle Feed Restrictors reduced by .004" to fix a rich idle!

Now thats some good information right there. I’m no carb specialist by any means…just know what i know through decades of trial and error. @Croz I would put those idle screws back were you found them and take the advice of ditching those plugs. When was the last time the carb was gone through? We are talking about a standard N/A 502 here, not a dual quad blower motor…this shouldn't be difficult. One variable at a time is usually best otherwise one can get lost in the weeds. Hell…the damn power valve could be stuck open for all we know.