Overheating - help - 4.3L

[GMTK]

2004 Volvo 4.3L GXI-E on a 2004 Hurricane SD187
Engine has 106 hours on it

Took the boat out today, leaving the dock the temp hit 200 and I knew we had issues. Turned back toward the ramp (1 mile) and hit 225 so I shut it down. Got a tow to the ramp and let it cool. Started it to put it back on the trailer. Engine did NOT sound normal. High pitched squeaking that was not normal.

Pulled off the hose from the water to the impeller - had HOT water in it.
Pulled off the hose from the impeller to the engine - had HOT water in it

The rest of the story - I put a new impeller in this morning. This was my first time doing this. Used an OEM impeller and it matched the one I pulled out. Followed the instructions to a T and made sure I put the hoses on the right spots and made sure everything was tight. One thing I did notice, when I pulled the housing off to start, there was no O-ring. I installed the o-ring that came with the kit. Started boat in the driveway using the fresh water inlet and a hose and it ran fine for 10 minutes.

Then took it to the lake and over heated. Going to pull the impeller off and look for damage.

What else do I need to look for to diagnose? Will check the oil dipstick. Boat was not winterized because we go out about once a month and it doesn't freeze in South Texas where we live.

Any help is appreciated.

 

[QBhoy]

Where the risers hot ? No doubt the my were. Could be caused by thermo stat not opening or perhaps exhaust flappers buggered and blocking the water passage outlet ?

 

[QBhoy]

"Were" not "where" haha.

 

[GMTK]

Yes. Put my hand on the impeller housing and it was super hot also. Just pulled the impeller off and it looks fine, only thing I noticed was on the spline, one of the peaks was shiny and slightly worn; but none of the others were. Only thing I can think is that I somehow switched the hoses when I put it back on. Oil looks fine also.

I was impressed with the motor that it shut itself down when it over heated. Now my worry is how much damage was done due the overheating (and figuring out why....)

 

[QBhoy]

If you have a trailer, could maybe run it up to temp on the hose and muffs to make sure water is coming out the back ?

 

[GMTK]

Just ran it via the water inlet on the engine for 10 minutes. Ran perfect. Sat around 160 and then I pushed the RPMs to 2500 and hit warmed to 175 then dropped back down. Impeller cover was cold to the touch. Outlet hose going up to thermostat housing was cold to touch. Risers were air-temp (75). I will say this, the large "trifecta" inlet that holds the thermostat was hot. The large tube coming from the water pump was hot. After I shut the engine down, the impeller cover was super hot and the risers warmed up. Not sure if this is normal or not. I'm at a loss.

 

[GMTK]

I spent the morning reading the volvo overheating pdf. Going to drop the boat in the water today and see what happens. I'm still learning how my engine fully works. I have rebuilt a 350 in an old truck, but I don't know a lot about the marine engines and how they function (how is excess water expelled, where does it expel, how hot should the thermostat cover be during run temp, etc).

 

[Senior B]

You have a flow problem. When your running it on the engine flush adapter, the water pressure from your hose is providing your flow and masking your issue. Get a set of Muffs and run it and see what happens when it's having to pull water up through the drive.

 

[bajaunderground]

Did your old impeller come out in one piece? If not, you need to find the pieces?

Was there any issue prior to the replacement? If not, you need to go back thru step by step.

You' re getting air somewhere? My money is on a pinched O ring, you don't have a sealed system, something was compromised during the swap?

 

[bajaunderground]

You have a flow problem. When your running it on the engine flush adapter, the water pressure from your hose is providing your flow and masking your issue. Get a set of Muffs and run it and see what happens when it's having to pull water up through the drive.

This will also mask as the water is still under residual pressure, albeit, to a lessor degree and thru the bypass

 

[GMTK]

Old impeller came out in one piece. No pieces broken off.

I did notice when I pulled the old impeller off there was no O-ring. When I installed the new impeller I put on the O-ring that came with the box.

Not going to bother with muffs, going to the lake after lunch.

 

[bruceb58]

...or perhaps exhaust flappers buggered and blocking the water passage outlet ?

There are no exhaust flappers in that year Volvo.

 

[GMTK]

Fixed the boat. Originally I thought the previous owner did not put in the O-ring on the impeller shaft. Welp. I was wrong. It was there. I didn't realize it. I thought the o-ring was supposed to be more like a washer, which I have now found out it's not. I pulled out the old o-ring, installed the new one and she ran like a champ. I did notice the new impeller dropped the temp about 3 degrees.

For anyone who later reads this thread (late at night, after a few bourbon's to kill the pain of a broken down boat), I'm going to provide some insight in to my problem.

But first - thank you to all the replies. The one that got me was from bajaunderground who told me about the sealed system. That got me to checking all the clamps and re-examining the impeller.

For starters - using the washout tube and hose will give you a false positive. I think the same will go for muffs. You really need a situation in which the impeller is forced to pull the water. Changing the impeller was actually incredibly easy and someone with even basic mechanical abilities can do it (at least for my model engine). But hooking up a garden hose won't necessarily prove it's working correctly.

A couple tale-tale signs that something was wrong (other than the temp gauge). I took temp readings while the engine was idling at the dock. This was with the engine running at idle for 5 minutes. Air temp was 80 and water temp in the lake was 64 degrees. The risers should be around 88-92 degrees. Once mine hit 125 I knew something was very wrong. The cover of the impeller was 65-68 degrees, water tube coming out of the water pump was 134 degrees and outlet tube from the thermostat housing to the engine was 102 degrees. These are just some baseline numbers for my engine working normally. When the engine was over-heating, the impeller cover got to 100. Another sign I could tell something was wrong, I drained the engine of water via the 4 ports. I then ran the boat at the lake for 3 minutes while diagnosing the problem. I then drained the ports again and there wasn't much water in them. This again told me there was an issue getting water up to the engine.

I'm grateful to have a good engine that shut itself down when it got to hot. Once the temp gauge hits 200 you have problems and start heading toward the ramp.

If anyone has corrections to my above post, please make them as I don't want to give out bad information.