YANMAR problem

[Garry Elmer]

Greetings!We've got a 2GM16 YANMAR Diesel in our Hunter 33. We put a new 3 bladed prop on at the beginning of the season. At full throttle, with a clean hull, we'd make almost 7 knots at 2950 RPM. Text book. Now, with some fouling on the hull and prop I can get to about 2500 RPM and 3/4 throttle and that's the best it will do. What I am concerned about is that if I push the throttle to full the engine bogs down, blows black smoke and put a ton of carbon into the water.Is this because the power required to push the boat is now more than the YANMAR can handle? Someone said I may have too much carbon built up in the mixing elbo of the exhaust. The all the fuel filters were just replaced.ThanksGarry http://www.99main.com/~elmergw/

 

[Pete]

check the elbow

you did not say what rpm you can get out of gear with no laod but if the set up worked good at the beginning of the season I would look for something else. like the elbow or a dirty hull (lots of marine growth). the elbow would be my first mechanical choice but also check for a fuel leak (did this happen before or after you changed the filters?)that will suck air into the system, giving similar symptoms. Good Luck!

 

[Steve Dion]

Don't forget to check your air filter too.

Garry:Do not forget to check the air filter too. Have you checked the prop for fouling?

 

[Ben]

I've a larger motor

I have a 2qm20 in my 1978 Hunter 33, and have had a 3 bladed 15x12 on it and it did fine pushing the boat at 6.5 at low rpm's. Engine mounts aren't so great so I don't rev it up much. It could be that a 16 horse motor isn't enough for our old, waterlogged boats? I'm sure mine doesn't weigh 10,600 anymore...but who knows until they weigh it huh?

 

[Tim Schaaf]

clean the bottom

I have the 2QM 15, which puts out about the same as yours. When the bottom gets dirty, or especially the prop and the shaft, or if I have lots of people and stuff aboard, or if my big alternator is really putting out, my engine bogs down a bit, too. There just is not much margin. Since I live aboard, full-time, and cruise a lot, my boat has a lot of stuff on it. I try to minimize, and the boat only weighed 12,000lbs at last haulout. Still,I am on the verge of taking an inch out of the pitch of the prop, to go a little easier on my faithful Yanmar.Clean everything up and see if it makes a difference.