Volvo Penta AQ200 overheating

[snoopy5]

Hi

Really hope someone can help me. I have a VP AQ200d with a 180 leg. We have been having overheating problems for the last year.

The boat will run all day at 1000rpm, temperature sits at 140 degrees but as soon as I speed up a bit to 1200 -1500 rpm the temperaure gauge starts to climb and goes up to 180 and into the red.

We have tried everything and I am at my wits end. It is a closed cooling system with raw water going through the heat exchanger to cool the fresh water which cools the engine.

The water pumps out of the leg no problem and the exhaust risers stay cool when travelling at 1000rpm. When I go faster the exhaust risers are too hot to touch but the raw water is still pumping from the leg.

I have replaced the impeller, thermostat, hoses, exhaust risers. Cleaned out the heat exchanger. Dont know what else to try !!!

I am thinking about reverting it back to raw water cooled and getting rid of the heat exchanger but this is expensive and I am not sure it will cool the problem.

The engine runs great, never had any problem with it except for the overheating.

Would really appreciate any help before I go completely crazy

 

[PiratePast40]

Re: Volvo Penta AQ200 overheating

any leak on the suction side will draw air into the cooling system. A common issue with these drives is the hose connection - number 27 in the drawing:http://www.volvopentastore.com/Intermediate-Housing-Aq-Drive-Unit-280/dm/*******.655437294--**********.940359430--store_id.366--view_id.327388

Corrosion on these is not allways visible from the outside so you need to remove the hose to check. The reason it doesn't overheat at idle is because the connection is under water at that time but is above water as speed increases. Change the gasket as well.

 

[snoopy5]

Re: Volvo Penta AQ200 overheating

Hi

Thanks for the reply. I checed the intermediate housing today, everything looks fine, removed the hose and replaced gasket. Still overheating. Not sure what to check next

any help appreciated