Volvo Penta AQ200d overheating at low revs

[snoopy5]

Hi Guys

Am at my wits end and hope someone can point me in the right direction. I have a Volvo Penta 200d with a 280 sterndrive.

Problem is that when the engine gets up to temperature (142 degrees) and I put it into idle, usually sits about 800-900 revs, the water stops pumping out of the sterndrive. As soon as I put the revs up a bit, about 1000, then the water starts to come out of the sterndrive.

I have replaced the impeller, even thought the old one is only 1 year old. Taken the engine pump off and it looks fine, no broken fins. Replaced the drive belt, taken off the exhaust manifolds and risers and given them a clean out (they were pretty clean anyway), replaced the thermostat and checked all the hoses.

Totally stumped as to what to do next, any help would be very welcome.

 

[captmello]

Is it overheating while in the water or just running on muffs? sometimes the pump won't draw water from the muffs very well without a good seal or too low water pressure.

Also, you could check the raw water pump housing and cover for scoring/grooves or any damage.

 

[snoopy5]

Hi

It is running in a tank (Large) of water with hose running. Getting plenty of water. This has just started a couple of weeks ago. Perfect until then. I have checked the water pump housing and no scoring or grooves.

 

[no704]

Check out the water neck on the top of the out drive, mine looked fine but after taking the hose off it was all but missing.

 

[jerryjerry05]

Maybe??? The cam in the pump is worn out?
The seal at the rear of the pump gone bad?
They used 2-3 different pumps, post a pic of the inside and the cover.
New impeller bad?

 

[snoopy5]

Hi guys

Will check the neck at the top of the outdrive, haven't done that yet but I cant see it being that or the sea water pump because it is pumping plenty of water above 1000 revs it is just when I put it into idle, 850 to 900 rmp's that the water stops.

 

[Scott Danforth]

you may want to run it on muffs vs a bucket. unless the bucket comes half way up the drive, your pump is loosing prime. its not ment to suck water that far.

 

[HorizonblueDK]

Before I replaced my Volvo manifolds with Mercruiser manifolds on my 4.3 engine, I had a similar problem. Well, when the boat was in the water, the temp started to rise and rise, when the engine was idling, and went down when I gave the engine just a few revs. The problem was that the old style Volvo V6 & V8 manifolds (before 1992 approx) tend to clog in the riser, just where the water exits and is being mixed with exhaust. The water passages in these risers are quite narrow and rust will over time build up and make these passages even smaller. But a few revs could apparently rise the pressure and force enough water through, to keep the engine cool.