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Old 28-07-2013, 09:11   #1
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Volvo Penta 2003 overheating - why?

I have a 2003 Volvo Penta engine with MS2 transmission and fresh water-cooling. The engine worked fine last year, but this season it overheats at high rpms. The only change we made over the winter was replacing the exhaust hose with a slightly longer one, which shouldnít matter. At 1500 RPM, it works fine with raw water coming out of the exhaust. At 2500 RPM in neutral it also works fine. At 2500 RPM with prop engaged, thereís a huge amount of steam coming out of the exhaust. This suggests to me that there is a blockage in the raw water system, but how do I find it?

Checked so far:
1)Sea water pump impeller. It had a large white shell in between two of the blades of the impeller. The impeller looked fine otherwise but I replaced it anyway. I had replaced the sea water pump itself a year ago.
2)Exhaust elbow. Iím told this is typically the cause of the problem. The old one looked ok, but I replaced it anyway.
3)Strainer. I dived under the boat. As far as I could tell there was no blockage. Itís just a bunch of very thin slits there and I was able to stick a screwdriver through them, but not very deep. Not sure how that white shell could have passed through there, unless it actually grew in size within the raw water system.
4)Heat Exchanger. Replaced it many years ago. Maybe I need to check it.
5)Hose loop attached to raw water thruhull. The hose is old but it doesnít collapse from the vacuum. Seems to work.

Questions:
1)The first place the raw water enters, after the thru-hull and small hose loop, is the MS2 transmission (see photos). Does someone know if the cooling rod can be removed from the MS2 and checked for blockage without removing the propeller shaft that is above it? Does anyone have any pdf diagrams of the MS2 so I could see whatís inside and how to take it apart?
2)I donít see a thermostat for the raw water side. I think I see what looks like a thermostat housing only for the fresh water coolant. Am I seeing this correctly?
3)Where else could the blockage be? Should I just take all parts of the system apart or is there another way to find the blockage?
4)Iím having trouble finding a mechanic with any free time to look at this. Any suggestions? The boat is in Norwalk, CT.

Aside:
The fresh-water engine coolant must also be getting too hot since itís not getting enough raw water cooling in the heat exchanger. It normally warms the hot water heater, but now Iíve got hot water coming out of the relief valve of the hot water heater into the bilge. If I turn off the domestic water pump so that the hot water heater does not fill from the water tanks, the engine overheat alarm goes off after about 20 minutes. This tells me that my domestic water system is now being used to partly cool the engine coolant; that eventually depletes all of the water in the fresh water tanks.

Any advice would be much appreciated.
Thanks,
Joe
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Old 28-07-2013, 09:14   #2
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Re: Volvo Penta 2003 overheating - why?

Sounds more like your prop or bottom is fouled since you don't have a problem not under load.

Has the boat been in the water for a while?

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Old 28-07-2013, 09:20   #3
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Re: Volvo Penta 2003 overheating - why?

Well, it seems to have had the steam from the exhaust problem ever since we put it in the water in May. I figured that engaging the prop just makes the engine work harder and therefore heat up faster.
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Old 28-07-2013, 10:23   #4
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Re: Volvo Penta 2003 overheating - why?

Quote:
Originally Posted by Joe500 View Post
I figured that engaging the prop just makes the engine work harder and therefore heat up faster.
exact ...

- control the thermostat in a pan of hot water
- descale the exchanger bundle with a suitable product (acid for boilers), be sure you've got the right seals before desmantling !
- check the pipe from pump to the exhaust (inside can be split and create a hernia)

./.
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Old 28-07-2013, 10:30   #5
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I'm wondering, if you had a shell between the impellor blades, could there be similar debris restricting the flow through the heat exchanger?
By the way, the engine would need to shed more heat under load - even at the same rpm, it's burning more fuel.
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Old 28-07-2013, 15:44   #6
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Re: Volvo Penta 2003 overheating - why?

Chase right through the salt water system. Mine had a lot of scale blocking the joints, but it was RWC.
There appears to be turbulence at the joints in the system.
How is your thermostat? The RWC one opens at 140 degrees, the FWC at 170. I Have a spare FWC thermostat somewhere, my boat had the wrong one when i bought it.
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Old 28-07-2013, 15:52   #7
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Re: Volvo Penta 2003 overheating - why?

How often do you change the coolant. It has anti-corrosives in it that wear out over a year or so. I had to flush and clean the coolant side of my old 2003 every 3 years or so with radiator cleaner to keep it cool.
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Old 28-07-2013, 19:05   #8
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On the 2003, we have found that some coolants will gunk up the fresh water pump. The first time this happened was after the boat sat for 2 years before we bought it. It was totally stopped up. 2nd time was when I replaces the pump, and found it 1/2 clogged. We asked a diesel mech, and he suggested rotella coolant as one that would not gel.
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Old 28-07-2013, 21:19   #9
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Re: Volvo Penta 2003 overheating - why?

We disassembled most of the raw water system today, but didn't find anything that could clog it. I was under the impression that lots of steam coming out of the exhaust suggests not enough of raw water flow. Could it mean something else? Some of you are suggesting checking the fresh water coolant. Would not enough fresh water circulation really cause the raw water to overheat? I figured not enough fresh water circulation might cause the engine itself to overheat but would not cause too much heat to be transferred to the raw water system (leading to steam out of the exhaust.)
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Old 29-07-2013, 02:09   #10
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Re: Volvo Penta 2003 overheating - why?

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Originally Posted by witzgall View Post
On the 2003, we have found that some coolants will gunk up the fresh water pump. The first time this happened was after the boat sat for 2 years before we bought it. It was totally stopped up. 2nd time was when I replaces the pump, and found it 1/2 clogged. We asked a diesel mech, and he suggested rotella coolant as one that would not gel.

a good coolant for cars or trucks will better protect the engine even during the winter, the expense is not huge, change every 2 or 3 years
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Old 29-07-2013, 05:21   #11
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Re: Volvo Penta 2003 overheating - why?

Joe, i am just wondering if something in his thread might be of interest
Overheating Volvo Penta MD2040
Cheers
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Old 29-07-2013, 06:23   #12
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Re: Volvo Penta 2003 overheating - why?

Unburned fuel in the exhaust from a bad injector can look like steam because it is white, or very light bluish white. A bad injector could also cause higher temps. Maybe have the injectors pop tested?

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Old 29-07-2013, 06:33   #13
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Re: Volvo Penta 2003 overheating - why?

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... Would not enough fresh water circulation really cause the raw water to overheat?....
Once the block overheats, the raw water is overheated too.
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Old 29-07-2013, 06:39   #14
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pirate Re: Volvo Penta 2003 overheating - why?

I remember a similar problem on an MD series engine in one of my boats a few years back... ended up taking the block of the side of the engine and finding the holes that the water passed through were so blocked solid the inner face looked flush... no holes... yet there were holes in the main engine.... a quick stabbing soon had all 4 holes cleared. Bolted everything back together and she ran beautifully.
As you may have gathered from the above description...
I'm not a mechanic merely an enthusiastic bodger...
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Old 29-07-2013, 06:51   #15
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Re: Volvo Penta 2003 overheating - why?

Did you pull the fresh water pump off of the engine?. We could not see the blockage until it was off the engine. A soak in white vinegar, and then a coolant flush, did the trick. We now plan onflushing the coolant once a year.

Chris

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We disassembled most of the raw water system today, but didn't find anything that could clog it. I was under the impression that lots of steam coming out of the exhaust suggests not enough of raw water flow. Could it mean something else? Some of you are suggesting checking the fresh water coolant. Would not enough fresh water circulation really cause the raw water to overheat? I figured not enough fresh water circulation might cause the engine itself to overheat but would not cause too much heat to be transferred to the raw water system (leading to steam out of the exhaust.)
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