engine problem

[ampro]

I have a 3 cylinder Volvo engine in my boat. Model MD 17 C and I can throttle up t5o 3,000 rpm but in gear it only revs to 1,500 rpm. I have an adjustable pitch blade but the pitch appears to be correct. any suggestions?

[sawingknots]

when its in gear and full throttle do you get lots of black smoke? if not try putting someone at the helm [be careful of revolving pulleys] force the Governor lever,do you get more rpm's if so your governor may be bad or out of adjustment,if no improvement you're not getting enough fuel because of clogged filter,clogged fuel lines,bad injection pump or bad injector

[TQA]

If it is not the VP prop and I know nothing about those at all.

Occams razor = clogged fuel filter.

Please change it before messing with the injector pump governor.

BTW If the governor was at fault you would not get 3000 RPM in the no load situation.

[ampro]

I have had the injector pump rebuilt , replaced one injector, replaced filters and replaced lift pump. I am running out of ideas but hate to sail with 50% power. Thanks for responding.This model has individual compression releases so I can test the cylinders individuallyJefdfd but all cylinders seem to be working correctly.

[sawingknots]

running at 3000 rpm's no load doesn't require much fuel,but under load its the governors job to regulate[supply] the extra fuel needed depending on the throttle position,if the governor is working properly and there's some other problem[bad trany bearing,fouled prop etc]there will be black smoke from the exhaust

[JimsCAL]

I would definitely double check the prop pitch. Too much pitch would cause the situation you have. What kind of speed can you make under power? If 5+ knots, you are making decent power and also points to the prop. If only about 3 or so, then could be the engine (or a REALLY dirty bottom).

[sawingknots]

i repeat!if for what ever reason your engine is under too much load there will be an excess of black smoke!!!,if there's not its not getting enough fuel

[TQA]

Originally Posted by sawingknots

i repeat!if for what ever reason your engine is under too much load there will be an excess of black smoke!!!,if there's not its not getting enough fuel

This would only be the case if the maximum fuel level has been set too high on the injector pump. If the pump is correctly adjusted there may be a small amount of black smoke when the engine is running with maximum fuel commanded or none at all.

However if you have a problem with a cylinder not combusting correctly due to injecto, piston or valve problems you would see smoke under load.

The rpm figure of 1500, is this a constant or does it vary depending on the speed of the boat.

If your variable pitch prop is stuck at in coarse pitch I would expect the rpm to increase as the boat accelerates from o knots and the prop unloads, perhaps not by much but 2 or 3 hundred rpm increase at least.

Is there any chance that your prop is badly fouled. Mine looked like a flower pot after just weeks in Rodney Bay.


If none of the above apply more details of the prop plus a full case history of what was done when and why might help with the diagnosis.

[ampro]

I dove on the prop to check it out and rotated it from forward to reverse and the pitch seemed correct.today the boat went about 4.5 knot5s at 1600 rpm. The motor has also been overheating. I have checked the pump, removed the thermostat, pulled out the exhaust hose and checked it for restrictions, checked the raw water inlet and strainer. Replaced fuel and filters, had the injector pump rebuilt, replaced an injector. Thanks to all for your replies. jeff

[sawingknots]

hmmmm, overheating could be cause by lack of fuel [running too lean]but also by an overloaded engine,theres lots of possibilities,btw have you tryed turning the prop shaft by hand [out of gear and engine not running],it should turn fairly easily,even a bad alternator bearing could create a big drag, i really hope you can solve this problem soon!