WELCOME TO RIVER DAVES PLACE

Why you change the impeller...

Mock Auntie

Well-Known Member
Joined
Jul 24, 2010
Messages
1,758
Reaction score
89
So we bought a boat. Used. Always garaged. Looked great, ran fine, clean. The guy had just had it out 3 weeks earlier without issue.
We took it to be serviced before dropping it in the water, the regular stuff, oil, etc...and the impeller. We asked him to save it so we could see what condition it was in. [emoji15] Holy crap!
This is what it looked like.
IMG_7115.JPG


On that note, what do you insist on doing maintenance wise to keep your boat running well?


Sent from my iPhone using Tapatalk
 
Joined
Dec 20, 2007
Messages
7,479
Reaction score
2,086
So we bought a boat. Used. Always garaged. Looked great, ran fine, clean. The guy had just had it out 3 weeks earlier without issue.
We took it to be serviced before dropping it in the water, the regular stuff, oil, etc...and the impeller. We asked him to save it so we could see what condition it was in. [emoji15] Holy crap!
This is what it looked like.
View attachment 665115

On that note, what do you insist on doing maintenance wise to keep your boat running well?


Sent from my iPhone using Tapatalk

Don't start it with out the hose hooked up...ever!

Check the engine oil, and outdrive levels.

Open the hatch every 15 minutes for the first hour you own it. Look for leaks and listen for squeaky alternator and water pump bearings. If the batteries are old, I'd recommend buying one new one.
 

Mock Auntie

Well-Known Member
Joined
Jul 24, 2010
Messages
1,758
Reaction score
89
Don't start it with out the hose hooked up...ever!

Check the engine oil, and outdrive levels.

Open the hatch every 15 minutes for the first hour you own it. Look for leaks and listen for squeaky alternator and water pump bearings. If the batteries are old, I'd recommend buying one new one.

Oh good thing you reminded me. I definitely need a new battery. We will do the 15 min checks too. Good idea.


Sent from my iPhone using Tapatalk
 

Rajobigguy

Well-Known Member
Joined
Aug 21, 2015
Messages
4,595
Reaction score
10,006
Don't start it with out the hose hooked up...ever!

Check the engine oil, and outdrive levels.

Open the hatch every 15 minutes for the first hour you own it. Look for leaks and listen for squeaky alternator and water pump bearings. If the batteries are old, I'd recommend buying one new one.



This. My impellers always go several years before changing and even then look in great shape. I attribute that to the fact that my boat is always started and warmed up at the house before driving it to the lake (about ten minutes away). In doing this it assure the the pump is always primed and taking in water immediately @ start up. Even if you never start your boat until it's in the lake you might be several seconds before the pump gets it's prime and starts working wet. Those few seconds of running dry can do a lot of damage.
 

HALLETT BOY

Well-Known Member
Joined
Oct 12, 2007
Messages
6,751
Reaction score
9,908
So we bought a boat. Used. Always garaged. Looked great, ran fine, clean. The guy had just had it out 3 weeks earlier without issue.
We took it to be serviced before dropping it in the water, the regular stuff, oil, etc...and the impeller. We asked him to save it so we could see what condition it was in. [emoji15] Holy crap!
This is what it looked like.
View attachment 665115

On that note, what do you insist on doing maintenance wise to keep your boat running well?


Sent from my iPhone using Tapatalk
Now you have take off every hose and retrieve all the broken pieces or the engine may run hot because of plugged passages in coolers / thermostat.
 

spectras only

Well-Known Member
Joined
Sep 20, 2007
Messages
13,076
Reaction score
12,814
The water pump should be primed before starting the engine. Some people start their engine/s while backing down on the ramp. I float my boat off the trailer so water makes its way to the pump , then start my engines. Even if there's good water pressure, it's advisable to change them out at 100hrs or before. I have SmartCraft system but have manual gauges as well to monitor water pressures. It's really easy to install and there's a plug on Merc thermostat housings [ location circled in picture ] where plastic tubing can be routed to a gauge on the dash.
Mercruiser%206,2%20L%20MPI
 

rrrr

Well-Known Member
Joined
Dec 19, 2007
Messages
14,984
Reaction score
32,543
So we bought a boat. Used. Always garaged. Looked great, ran fine, clean. The guy had just had it out 3 weeks earlier without issue.
We took it to be serviced before dropping it in the water, the regular stuff, oil, etc...and the impeller. We asked him to save it so we could see what condition it was in. [emoji15] Holy crap!
This is what it looked like.
View attachment 665115

On that note, what do you insist on doing maintenance wise to keep your boat running well?


Sent from my iPhone using Tapatalk

"It doesn't hurt to start it on the trailer if you just run it a few seconds."

Smart idea to have it serviced before loading up everybody and everything. That trip would have ended quickly.

It's nice to see you posting, especially with a new boat.
 

rrrr

Well-Known Member
Joined
Dec 19, 2007
Messages
14,984
Reaction score
32,543
Oh good thing you reminded me. I definitely need a new battery. We will do the 15 min checks too. Good idea.


Sent from my iPhone using Tapatalk

Also open the hatch and look closely after the first time you fuel it, always run the blower before starting, and do another engine check a few minutes after you leave the fuel dock.

Gotta be safe.
 

Boat 405

Well-Known Member
Joined
Dec 20, 2007
Messages
4,441
Reaction score
7,961
Sea strainers offer a good buffer of about 1/2 a gallon so the impeller is always seeing water even if it hasn’t been started in a while. My sea strainer always stays full even after towing hundreds of miles.
 

Attachments

  • FA7816B9-1A9E-474F-ADAE-187758EB7A8E.jpeg
    FA7816B9-1A9E-474F-ADAE-187758EB7A8E.jpeg
    271.1 KB · Views: 175
  • DBB394B7-EE3E-492F-8592-120322AB4C98.jpeg
    DBB394B7-EE3E-492F-8592-120322AB4C98.jpeg
    211.2 KB · Views: 180

NicPaus

Well-Known Member
Joined
Sep 15, 2010
Messages
12,973
Reaction score
12,379
That impeller is toast. No way it was moving any water. Ran dry for a while. First run make sure check oil looking like that it migt need a head gasket....
 

lbhsbz

Well-Known Member
Joined
Jan 11, 2010
Messages
11,666
Reaction score
28,505
The only time I'll ever dry fire my merc (outboard) is on the old impeller after the season is done but before the first trip of the next season, and I put an impeller in it before every season without question...also change the lower unit oil. My impellers will only spin dry if I never plan on putting them in the water again.

Even after the abuse I put mine through, they always look fine...but they don't work. You might get away with spinning it backwards after the season to flip the vanes so they don't take a set and lose tension against the housing in the right direction, but you're still on borrowed time...unless it's an OMC impeller....they last forever.
 

boatdoc55

Rest Easy Retired Boat Mechanic 😢🚤
Joined
Jan 28, 2011
Messages
7,814
Reaction score
11,272
The only time I'll ever dry fire my merc (outboard) is on the old impeller after the season is done but before the first trip of the next season, and I put an impeller in it before every season without question...also change the lower unit oil. My impellers will only spin dry if I never plan on putting them in the water again.

Even after the abuse I put mine through, they always look fine...but they don't work. You might get away with spinning it backwards after the season to flip the vanes so they don't take a set and lose tension against the housing in the right direction, but you're still on borrowed time...unless it's an OMC impeller....they last forever.
OMC high volume/low pressure = yes OMC high pressure/low volume= same as mercury. Change it out.
 

Mock Auntie

Well-Known Member
Joined
Jul 24, 2010
Messages
1,758
Reaction score
89
The water pump should be primed before starting the engine. Some people start their engine/s while backing down on the ramp. I float my boat off the trailer so water makes its way to the pump , then start my engines. Even if there's good water pressure, it's advisable to change them out at 100hrs or before. I have SmartCraft system but have manual gauges as well to monitor water pressures. It's really easy to install and there's a plug on Merc thermostat housings [ location circled in picture ] where plastic tubing can be routed to a gauge on the dash.
Mercruiser%206,2%20L%20MPI

It will be staying in the water in a covered slip so I should be good, right?


Sent from my iPhone using Tapatalk
 

Mock Auntie

Well-Known Member
Joined
Jul 24, 2010
Messages
1,758
Reaction score
89
The only time I'll ever dry fire my merc (outboard) is on the old impeller after the season is done but before the first trip of the next season, and I put an impeller in it before every season without question...also change the lower unit oil. My impellers will only spin dry if I never plan on putting them in the water again.

Even after the abuse I put mine through, they always look fine...but they don't work. You might get away with spinning it backwards after the season to flip the vanes so they don't take a set and lose tension against the housing in the right direction, but you're still on borrowed time...unless it's an OMC impeller....they last forever.

This one is an OMC actually so I wouldn’t say forever
We’ve always changed them every year. This guy had the boat since 2011 and had never changed it. [emoji15] I don’t know how he had it in the water three weeks before we bought it.


Sent from my iPhone using Tapatalk
 

RiverDave

In it to win it
Joined
Sep 13, 2007
Messages
123,232
Reaction score
150,642
Anyone have any thoughts on those blue lifetime impellers?
 

spectras only

Well-Known Member
Joined
Sep 20, 2007
Messages
13,076
Reaction score
12,814
Anyone have any thoughts on those blue lifetime impellers?
I have thought of trying them but read mixed reviews on them. Seeing that it has less blades then Mercs, it may not deliver the required volume/psi at high rpm's. Some might have first hand knowledge about it here.
 

Pesky Varmint

Well-Known Member
Joined
May 12, 2013
Messages
276
Reaction score
390
I put fresh impellers in at the start of every season whether it needs it or not. It is so much less expensive and a lot
less hassle than if I have any type of impeller problem on the water. But then again the water pumps on my 575SCi's
are actually pretty easy access. Not true for some other engines. This is how I've been doing it since buying the boat
in 2001.
 

boatdoc55

Rest Easy Retired Boat Mechanic 😢🚤
Joined
Jan 28, 2011
Messages
7,814
Reaction score
11,272
Anyone have any thoughts on those blue lifetime impellers?
Dave, My shop tried the blue one's from "Barco" many, many moons ago and found they were total JUNK!! I really doubt the one's from the modern era could be as bad as those were. They really had the sales pitch back then and we had a bunch of them for many applications and once we had a couple fail they were all returned and the boss refunded.
 

OLDRAAT

inadequate member
Joined
Oct 3, 2007
Messages
2,617
Reaction score
4,068
Me thinks the blue impellers are softer and more flexible resulting in less contact pressure on the housing bore resulting in what Spectras stated above based on some I tried a few years back. Pressure and volume reduction appeared to be a correct statement.

OR
 

Echo Lodge

Well-Known Member
Joined
Aug 27, 2009
Messages
3,385
Reaction score
5,253
Buddies roll bar boat had his pump detonate last weekend. Its a 2001 Roll Bar with a Merc that has 800 hours on it. He changes the impeller regularly (year to year and half) and boat gets used year round. I was surprised his raw water pump has a plastic housing. My Nautiques run Sherwood metal housing pumps. My first Nautique 1990 has 2k hours on it and is still on its original pump.

9b0eef67-3794-43d3-bbae-4e0c9d7a27c7.jpg
b0ceb866-1924-4cc7-8670-410f6c745674.jpg
f7bcfbc5-e7f3-41af-bc8a-d5beb1aca22d.jpg
 

Deja_Vu

Essex Affectionado
Joined
Aug 4, 2014
Messages
6,262
Reaction score
4,758
Wow that impeller was baked into a chocolate cupcake. :eek: Glad you caught it.
I usually have my impeller changed out every other year. I didn't think to ask to see the old one.
 

OC Mike

Well-Known Member
Joined
Feb 14, 2018
Messages
914
Reaction score
2,070
****Edited****

The Mercury 525/600/700 are psi/flow sensitive. Cracked headers on the port side are not uncommon, mostly from lack of flow.
I went down an internet hole looking for info awhile back.
Here's what I found out.
One can have pressure, but lack flow. Our gauges register PSI, not flow, so we don't know.

There is a test somewhere on the net using a 525/500 EFI talking about flow and PSI.
Took a flow and psi reading on used impeller. ...Deleted.....
Replaced housing, impeller and plate spacers, flow improved dramatically, with similar pressure.

I read elsewhere from some builder the Silicone impellers are more flexible so have less flow than the Mercury impeller. Thus does not recommend with headers.
Probably OK in non performance engines. I realize this is here say......


Summary,
1. PSI and flow are related but different. Possible to have good PSI with lack of flow.
2. Bravo Pump works fine with all new components, housing impeller and plate spacers.
Housing and plates do degrade.
3. Blue, silicone impeller not suitable for Mercury 600/700.
4. Bravo pump needs top be at peak efficiency for Merc 600/700.


If I find the video, I'll post it.
 
Last edited:

Runs2rch

Well-Known Member
Joined
Jun 10, 2013
Messages
9,455
Reaction score
9,445
I change mine every other year, they come out looking pretty good. They have ~75 hours on them.

Same here. I run the Hardin housing. New wear plates each time also. Easy on any beaching, and I always float the boat off. To keep sand ingestion to a minimum.
 

Ragged Edge

Man in the Box
Joined
May 4, 2011
Messages
2,073
Reaction score
2,473
Buddies roll bar boat had his pump detonate last weekend. Its a 2001 Roll Bar with a Merc that has 800 hours on it. He changes the impeller regularly (year to year and half) and boat gets used year round. I was surprised his raw water pump has a plastic housing. My Nautiques run Sherwood metal housing pumps. My first Nautique 1990 has 2k hours on it and is still on its original pump.

View attachment 665189
The pump body does not melt like that unless it has been run dry for awhile. Did he pick something up that blocked the water intake?
 

OC Mike

Well-Known Member
Joined
Feb 14, 2018
Messages
914
Reaction score
2,070
I found the video.
It's done by CMI regarding the overheating on their headers.
They are obvioulsy sensitive about the overheating issue.
My memory was off a litttle on a few specifics. One is the test is on a 500/525 EFI engine, not a 600.
The flow issue compounds on the 600/700 as the intercooler shares the water.

Not sure where I read about the Blue, silicone impeller.
What I did read was it was more flexibile, as a result it didn't flow as much.

Your results may vary....
 

Bigbore500r

Well-Known Member
Joined
Apr 28, 2014
Messages
17,360
Reaction score
35,090
I think Merc rates the pump for 10 seconds dry before issues arise*. Not that I advocate pushing the limit.

* JET BOTES - go ahead and fire that bitch up in the parking lot, and rev it till the valves float for a few minutes till it's your turn at the ramp
 

lbhsbz

Well-Known Member
Joined
Jan 11, 2010
Messages
11,666
Reaction score
28,505
OMC high volume/low pressure = yes OMC high pressure/low volume= same as mercury. Change it out.

We had an old 100hp evinrude that we probably ran 10 years with the impeller that was in it when we got it...never an issue. Merc shoulda taken notes.
 

Ziggy

SlumLord
Joined
Sep 20, 2007
Messages
38,885
Reaction score
43,230
I've had new impellers put in twice in the past 100hrs on boat. 3rd full season on the boat, 3rd impeller.
 

bocco

Well-Known Member
Joined
Mar 8, 2008
Messages
2,176
Reaction score
2,288
Keeping the impeller wet rally makes the different. I had a houseboat with an OMC King Cobra drive. It stayed in the water for about 7 years between haul outs. After 7 years the impeller always looked perfect.
 

mash on it

Beyond Hell Crew
Joined
Jan 26, 2011
Messages
3,602
Reaction score
5,371
* JET BOTES - go ahead and fire that bitch up in the parking lot, and rev it till the valves float for a few minutes till it's your turn at the ramp

Even you know the points float before the valves. However, the impeller will last a little longer than a year, and not a 'yearly maintenance' item. ,
$325+ for an aluminum one, and mines stainless...should last forever.

I'm just a ditch pump degenerate...

Dan'l
 

Bigbore500r

Well-Known Member
Joined
Apr 28, 2014
Messages
17,360
Reaction score
35,090
Even you know the points float before the valves. However, the impeller will last a little longer than a year, and not a 'yearly maintenance' item. ,
$325+ for an aluminum one, and mines stainless...should last forever.

I'm just a ditch pump degenerate...

Dan'l
Unless you have a dual point distributor!
 

boatdoc55

Rest Easy Retired Boat Mechanic 😢🚤
Joined
Jan 28, 2011
Messages
7,814
Reaction score
11,272
We had an old 100hp evinrude that we probably ran 10 years with the impeller that was in it when we got it...never an issue. Merc shoulda taken notes.
Yes, those were the high volume pumps with very long blades on the impeller. Those long blades were very forgiving. I have taken some old, old OMC stern drives apart over the years and found impellers still in one piece after 24 years. The blades are darn near 3 inches long.
 

highvoltagehands

Laveycraft Nuera 2750
Joined
Jan 17, 2008
Messages
2,672
Reaction score
3,398
The water pump should be primed before starting the engine. Some people start their engine/s while backing down on the ramp. I float my boat off the trailer so water makes its way to the pump , then start my engines. Even if there's good water pressure, it's advisable to change them out at 100hrs or before.
/QUOTE]

I never float off, I always start my boat while it's still on trailer & in the water and then drive it off. That way I prove engine starts and drive works while on the trailer. If it doesn't, I can just pull right back out instead of floating around with dead boat fouling the ramp area.
 

Bpracing1127

Well-Known Member
Joined
May 31, 2012
Messages
10,018
Reaction score
12,892
I do mine every year as part of my yearly maintenance. It’s always comes out in tact, but you can see small hairline cracks at the base of the fins. I could go another year on it but it’s cheap insurance.
 

Echo Lodge

Well-Known Member
Joined
Aug 27, 2009
Messages
3,385
Reaction score
5,253
The pump body does not melt like that unless it has been run dry for awhile. Did he pick something up that blocked the water intake?

Same question I asked him. He never starts it on land either. Last season during one really low water Thursday boat was in the sand pretty good even though the back end was kicked out. Took us 20 mins to free it. Might have had some sand stuck in the grate but boat has many trips on it since. I do like the fact my Nautiques have a strainer so the pump gets primed right away.
 
Last edited:

Blackmagic94

Well-Known Member
Joined
Apr 4, 2017
Messages
5,252
Reaction score
7,222
What a lot of people don’t understand as well is debris kills more impellers then lack of water to cool the blades.


You start that motor up on the beach of pirates cove or the sand bar and you are sucking sand. That sand will destroy blades. If your boat is not some massive pig of 10k lbs like mine then you should always follow the rule of the “sea lice”, never start a motor while part of the craft is on the beach, never start a motor if the water isn’t 3’ deep.

With raw water systems, it’s hard to know when this happens as you just shit the mud out the tail pipes, try it with a closed cooling system like a 496 mag and you will find out real quick that sand or silt will clog and overheat the motor in a few minutes of idle
 
Top