2004 5.7 GXI Overheat - Pump? Impeller?

[MCNPathfinder]

Good evening all you wonderful folks. I have a 2004 Volvo Penta 5.7. Recently had it on vacation at the lake all week. I bought a few things with in case we encountered issues. The first time out wakeboarding, I wasn't paying attention to the heat and I got the dreaded beep. Brought a new impeller for the raw water pump with and replaced on the water. Still got hot again and beeped. This time we took apart the thermostat housing and found a piece of an old impeller (the one I removed prior that day was still intact, so this was well before I owned it).

I did notice that there were some drips from the raw water pump. Seemed like they were coming from some like weep holes? I assume this is not normal behavior. Boat does get hot, but when the gauge says 180 we had been backing it off. Once it cooled down we could run at 3k and about 170 degrees for hours.

So it seems like the engine is not getting enough water to cool it down. Didn't really have any issues last season. I'm leaning towards rebuilding that raw water pump because of the drips. Would a leak from a weep hole that small cause an overheat?

I'm also going to be replacing the thermostat. It had a 160, I'm going down to a 150 (unless you all think that's a bad idea).

We ensured water was being pumped by removing hoses one by one from the thermostat housing and starting the engine briefly to see water being pumped out. I'm also going to clean up the housing a bit and maybe crack open the exhaust risers. As well as just flush everything out clean. I don't trust that there aren't any additional pieces of impeller in there.

Thank you!

 

[ESGWheel]

Let’s see if we can get the conversation started and get you back on the water with confidence.

First off, a small drip fm the Raw Water Pump (RWP) would not impact the temps. And putting in a 150 t-stat is not addressing the root cause.

A little more info on the boat would be helpful. Examples: this is a new to you boat, this being your second season and your during your first season no overheating heating issues whatsoever; what maintenance have you done; engine serial no.; etc.

And in the meantime, yes backflushing everything and pulling the risers to look at their condition is a great start.

Also, with the age of your pump, even with a new impeller, if the housing is worn away or gouged (think of sand and small pebbles flowing thru it) it may not pump to its needed specs. So take a close look at that as well.

 

[Scott Danforth]

Check the raw water supply fitting at the forward edge of the outdrive where the hose attaches. If corroded, replace it

Guessing this is a new to you boat. What other maintenance have you done they the prior owner neglected?

 

[GMTK]

I made a rookie mistake when I put on a new impeller and forgot to pull the old o-ring off and installed a new one - thus had two o-rings and the impeller wouldn't work properly. Hope you figure this out, good luck.

 

[MCNPathfinder]

Thanks for the replies all! This is my second season with the boat. Bought it July of 2024. Had no issues for the remainder of the first season. Had it winterized and it's been one thing after another.

I noticed it get a little hot last year one time. So I figured it was due for a new raw water impeller. I bought one proactively in case it acted up last week on vacation. We put it in on the water and flushed as much as we could. I suspect there are more pieces of broken impeller in the system.

I plan on pulling apart the impeller housing to check things again. Hopefully there's nothing wrong in doing it (I've done it three times), but I haven't ever actually inspected the housing for grooves, etc.

I found the VP Overheat Diagnosis PDF and loosely followed that with things I had on hand, but now that I'm home I think I could set myself up a bit better.

I'm not exactly sure what to do about testing. I doubt that I'll be able to run it fast enough in the driveway to test for overheat. Muffs and the hose attachment are really only for idle throttle, right?

Thanks again all!

 

[ESGWheel]

Correct, on muffs, do not run it up, perhaps 1500 max but only for 10 seconds or so.

Also, you may be able to run it on a hose without muffs connection. Read the attached.

While you cannot replicate running it on the lake you can still do your investigation per above. Also please provide what maintenance has been done by you. Thanks.

 

[MCNPathfinder]

Thank you ESGWheel! I'm filing that away! In terms of maintenance, I have not done much to it to be perfectly honest. It was sold to me in July 2024 as a turnkey boat and it definitely was/is.

Here's what I have:
-Purchased 7/2024.
-Winterized (Professionally) 10/2024.
--Engine drained and winterized.
--Outdrive gear oil changed.
--Oil and filter changed.
--Fuel filter changed (although to the short one).
--Fuel treated.
-De-winterized by me 5/2025. Had fuel issues, changed to larger OEM fuel filter (I don't think either of us had the fuel filter screwed all the way on).
-Raw water impeller 7/2025.

I think that's about the extent of what I've done. I know the raw water impeller has been changed at least once before because I removed a piece of it from the thermostat housing. We also removed the thermostat housing and put the whole thing in a pot of boiling water to ensure it was working.

 

[ESGWheel]

OK, now time to get to work Do all that backflushing and checks as per above. Pulling off the hoses will be much easier with a tool set like this link. If you do not have one, trust me, get it. Also while pulling hoses give them a squeeze in the middle. Does it feel like you are crumpling a ball of aluminum foil? Do they make a crackling noise? If yes, time to replace. Being an ’04, they have lived their life so while correcting this overheat issue good time for some preventive maintenance.

Here is a link to get you diagrams and part nos. And here are some additional good places to get OEM parts:

• Doug Russel Marine link
• Leaders RPM link
• Cecil Marine link

 

[Scott Danforth]

Here is the most up to date parts lists.

Volvo Penta Shop

Find and buy the full Volvo Penta aftermarket assortment for marine and industrial applications. With more than 200.000 genuine parts to support all maintenance and repair you will find all you need. Identify the Volvo Penta engine, shield or drive when looking for spare parts, maintenance...

www.volvopenta.com

 

[Donald0039]

Lower temp thermostat is for a RWC cooled engine running in salt water typically.

The raw water pump has an O-ring. That needs to be on good shape.

The raw water pump has a shaft seal and a bearing. The shaft seal is pretty easy to replace but the bearing needs a bearing puller, and an arbor press. I do not believe VP sells an replacement bearing, just a seal. The new raw water pump is $450 roughly.

The engine also has a circulation pump that probably has weep holes. That pump has a bronze or similar impeller so the impeller never fails but the seal or bearing might

 

[Donald0039]

Also an IR thermometer can be handy. And when you get everything fixed take baseline temps of various components.