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:
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.
. 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.
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.
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.