I’m lacking a bit of oomph
QMy Volvo Penta 2010 engine loses power and when out of gear only revs to 2,500 (on the cable-driven mechanical counter), when it used to reach 3,600rpm. I’ve changed the fuel filter, done an oil change and there is the normal amount of water coming out of the exhaust. A REID, via email
ATONY REPLIES: If the wet exhaust system is partially blocked it might still allow the raw water pump to deliver its full output, but back-pressure in the exhaust may be limiting the engine power.
Disconnect the exhaust from the mixing elbow and inspect the elbow for internal furring. Try the engine with the exhaust disconnected (it will make a real racket) – if you then get the revs, it’s an exhaust problem – probably a delaminating hose. Also, try it with the air cleaner off. If that solves it, the cleaner is blocked. Be sure that there is at least 3 to 6sq in of vent area allowing air into the engine area. I have had such problems when boaters have used closed-cell foam on the deck board supports.
Next, consider a lack of fuel. Did you turn the fuel tap back on fully after servicing the filter? Is there a filter on the engine or a water trap (which may contain a filter or strainer) between the tank and engine.
Is there a gauze in the top of the liftpump? Is there a gauze strainer on the end of the fuel pickup pipe inside the tank? Are all these clean? Double-check all unions between the tank and lift pump to ensure there are no slight air leaks.
It is possible that the liftpump is starting to fail: check by rigging a small gravity feed tank that supplies fuel directly to the lift pump or filter.
Check exhausts for internal furring