Yanmar 1 GM 10 power issue

[CAPTMIKE5]

I own a 1985 1GM10 that presently is running, in fwd gear at only 2300 RPMs. The engine runs fine without the transmission in fwd and reverse, fine with the transmission in fwd and reverse ( I do find the tranny runs hot but I cant say if this is normal or not) but when I add the shaft and prop I only get 2300 RPMs fwd and its fine running aft. She also emits carbon in the exhaust if I raise the RPMs to quickly in fwd. In fact I have to raise them very slowly to avoid this.

ANY suggestions

Mike

 

[sailaway78]

First suggestion

Is a dirty prop. I did not believe that barnacles on the prop could make one act like that, untill it happened to me. My 3GM would only turn up 2100 at full throttle, smoked a lot, and blew some soot out. After a short dive to clean the prop, all was back to normal. This may not be your problem, but is the first place I would check. The other usual suspect is the exhaust elbow being carboned up.