Volvo penta d6310 overheat at hi rpm

Our engine overheats at hi rpm

Our engine overheats at hi rpm if there is the tiniest amount of debris in the Raw Water Strainer but is otherwise normal. Cool down is almost instantaneous if the rpm is reduced by 300. I wonder if the raw water pump or system is fitted with a relief valve which is operating to cause this fault and where it is located. The strainer is cleaned prior to each trip but we travel in a lot of shallow water. Thanks for your help.

"When was the raw water impell

"When was the raw water impellor change?. Also if this is a diesel. The first rule of owning a diesel is if your having any problems change the fuel filters. If your fuel filter(s) are clogged up your not getting enough volume of fuel, the fuel also is used to cool the head. I have seen this happen alot."

"Thanks Captain!
I like the p

"Thanks Captain!
I like the pactical solutions first
I checked the log and the fuel filters were changed 5 months ago as were the raw water impellors, (we have been chasing this problem for nearly a year now) Re the fuel flow suggestion, I guess this is because a large proportion of fuel is returned to the tank from the engine and this would reduce if fuel filters block. Should the fuel return pipe always be at "engine room temp"? The manual says I should get code 1.7.9 or 1.9.7 if the fuel pressure is low or the fuel temp is hi (but I'm not sure where it measures fuel temp anyway)The odd think is we can tow boats at similar throttle settings without problems but when we are at speed this problem seems strongly related to rpm ie onset and recovery are rapid and 300rpm less will run all day. Thanks for your suggestion. I will replace the filter again if I can't resolve this soon."

"If speed related, check the w

"If speed related, check the water inntake, If possible hook a clear pastic hose between inntake and pump and watch for air bubles, or do a dive and clean the inntake."

"Thanks for the advice re wate

"Thanks for the advice re water intake, the problem has been repaired now. I checked the intake and installed hose to look for bubbles,waterflow slowed down at hi speed and revs. The flexible hose from leg to water pump had a weak spot and was collapsing under hi suction of hi revs. Hose replaced runs without overheat now. Thanks once again for your advice"

"had same problem, remove and

"had same problem, remove and clean out the exhaust elbow. solved my problem."

i have a broome european 35 wi

i have a broome european 35 with twin volvo tmd 40 problem with port engine above 2000 revs exhaust steams have been told could be air lock or heat exchanger blocked any clues or advice welcome dave