engine overheat, PROBLEM SOLVED

kevincave · Jul 29, 2011

i have a 1985 aq 125b 4cyl volvo motor, at idle speed the engine runs at 180 degrees, at speed it quickly rises towards 240 degrees, slow to idle speed and it goes back to 180...

Don S · Jul 29, 2011

Re: engine heating up

Re: engine heating up

When was the last time the impeller was replaced?

kevincave · Jul 29, 2011

Re: engine heating up

Re: engine heating up

this is the first time i have had the boat out, bought it about a month ago. got home and pulled the impeller, looks good, soft pliable rubber. was kind of scrunched up in the housing and i am wondering about the rotation direction of the impeller blades..

jerryjerry05 · Jul 30, 2011

Re: engine heating up

Re: engine heating up

That motor has three places to look.The exhaust manifold.Would be the first place I'd look.Remove it and check the end for corrosion and blockage.
The second is the heat exchanger.It blocks with sand and mud and will cause a slow overheat.
Then the pump.The vanes are self orienting.
If the seal is bad it can suck air.The brass might have scoring and not seal tight enough.Then the cam might be worn or the impeller bad.J

kevincave · Jul 30, 2011

Re: engine heating up

Re: engine heating up

thank you, i now have a direction to go in....kc

sqbtr · Jul 30, 2011

Re: engine heating up

Re: engine heating up

Don't forget the water neck at the top of the intermediate section

Don S · Jul 30, 2011

Re: engine heating up

Re: engine heating up

looks good, soft pliable rubber. was kind of scrunched up in the housing and i am wondering about the rotation direction of the impeller blades..

If the blades did not straighten out after about 10 minutes, then the impeller is junk. If you didn't put on a new gasket, the pump may be sucking air and it won't cool.

kevincave · Jul 30, 2011

Re: engine heating up

Re: engine heating up

update, impeller did strighten up after a few minutes, found part of an old impeller in the heat exchanger. flushing it now, going to clean the hoses and tubes and try to clean and flush the whole sea water system. does the anti freeze fluid tank have anything to do with heat exchanging, could it have been contaminated? it has a removable cover on the front..thanks you guys are a tremendous resource..kc

kevincave · Jul 30, 2011

Re: engine heating up STILL !!!!

Re: engine heating up STILL !!!!

got the system cleaned, ran water hose directly into intake pipe, dumps a bunch of water out the exhaust ran at 3000 rpm in the driveway, didnt go over 180degrees, took it to the lake, ran 180 at idle all through the 5mph zone, soon as i took it to 3000 rpm temp started rising to 240,, ???? any ideas???

captmello · Jul 31, 2011

Re: engine heating up

Re: engine heating up

sqbtr said:
Don't forget the water neck at the top of the intermediate section

check this. it is the fitting with the water intake hose, just under the ujoint bellows. remove the hose from the fitting and check the fitting for corrosion.

Maclin · Jul 31, 2011

Re: engine heating up

Re: engine heating up

Kevin, the fitting captmello mentions is under water at slow speeds so even if it is "bad" the impeller still "sees" all water so it keeps prime and water flow is good. Once the boat begins to plane out that part of the drive is above the water and can leak air and thus the impeller loses suction.

The engine shold not heat up immediately though, should be a steady rise in temp after a few minutes. And if you slow down to non-wake speeds again it should cool down if that fitting is the problem

kevincave · Jul 31, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

going to check the fitting first thing, it is definately a water flow problem. when i by passed that section with the garden hose it ran cool. it does heat up within 3 minutes, the goes back to 180 rather quickly when slowed to idle speed. thanks again...

kevincave · Jul 31, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

ok, got to the water neck, found the bushing and seal beneath the water neck shot. i would imagine on a plane it would suck air from there before drawing water. going to split the lower end r, replace all the bushings, seals, orings. does this sound like whats causing the problem? thanks kc

Maclin · Jul 31, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

kevincave said:
.....does this sound like whats causing the problem? thanks kc

Yes.

scb1712 · Aug 1, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

Hi All,

We're having a similar problem with our 2000 Volvo Penta 3.0L. We discovered that 3 of the 4 channels on the exhaust riser were completely clogged with rust from previous salt water use. However, i would like to check the "water neck" on ours. I'm new to this as this is my first boat (but know my way around car enqines very well) - so i'm not certain where the water neck is. Would anyone have a schematic or diagram of it?

RogersJetboat454 · Aug 1, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

scb1712 said:
Hi All,

We're having a similar problem with our 2000 Volvo Penta 3.0L. We discovered that 3 of the 4 channels on the exhaust riser were completely clogged with rust from previous salt water use. However, i would like to check the "water neck" on ours. I'm new to this as this is my first boat (but know my way around car enqines very well) - so i'm not certain where the water neck is. Would anyone have a schematic or diagram of it?

Welcome to Iboats.
The drive on your boat does not have a water neck like the old 200 series drives this thread is related to.
In any case, you need to start a new thread, as it is not polite to the original poster to hijack his. Starting a new thread will also get more/better answers

.

kevincave · Aug 11, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

got the parts yesterday, all new seals bushings and orings to renew the water/steering tube. testing out fri morning...

kevincave · Aug 13, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

problem solved, thanks for the help. how did we live without the internet??

captmello · Aug 14, 2011

Re: engine heating up NEED HELP

Re: engine heating up NEED HELP

Glad to see you got it fixed. I did mine a couple years back. Many seem to resort to thru hull intakes when reaching your point. Fixing it correctly is usually the best, IMO.

whitecrystal1 · Aug 14, 2011

Re: engine heating up

Re: engine heating up

jerryjerry05 said:
That motor has three places to look.The exhaust manifold.Would be the first place I'd look.Remove it and check the end for corrosion and blockage.
The second is the heat exchanger.It blocks with sand and mud and will cause a slow overheat.
Then the pump.The vanes are self orienting.
If the seal is bad it can suck air.The brass might have scoring and not seal tight enough.Then the cam might be worn or the impeller bad.J

This is not always true. I just went through this problem last week helping my Father-in-Law fix his overheating issue on his boat. His impeller was installed backwards when it was winterized last year. When we took it out this year we found it kept over heating anytime the engine was at idle. If the RPM's were raised to 1300-1400 if would not overheat at all.
After pulling the T-stat housing cleaning everything up and pulling the exhaust elbow not seeing anything wrong yet it was still overheating we pulled the impeller and seen it was backwards.. replaced it again and all is good now

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