Yanmar 2GM20F

[psteele235]

My Fraser 30 is a 30 foot sloop with 8,500 lbs displacement.

The Yanmar runs a 14 X8 RH3B prop. I get 4 1/2 knots at 2800rpm and then black smoke at 2,900 - 3,000WOT.

Should I get more RPM and speed? And could this be the prop?

Thanks in advance to anyone who can help.

[never monday]

what is the water line length? the waterline beam? and gear ratio of your KM2 gear?

[Evan]

Yes, you are over-propped by your description of max RPM. However a 14x8 is not a "big" prop for a 2GM20. Positive that is the prop size and real pitch?

If the prop and bottom is clean, then you should be able to get maximum RPM in calm water, or 3600 RPM. If you can't you are not getting full power from the engine and you are "lugging" the engine. Easiest fix is pull the prop and see if your local prop shop has a tester you could try. Try something with less diameter and pitch - and ask them to measure your existing prop because it should be pretty close to spot on, if a bit too small; unless it's a 3 blade motorboat prop with a lot of area.

[psteele235]

Originally Posted by never monday

what is the water line length? the waterline beam? and gear ratio of your KM2 gear?

Survey says:
30 feet LWL, 9'7" beam.
Fixed, three-blade cast bronze propeller stamped to indicate 14” diameter 8’” pitch and right hand rotation.
Gear Kanzaki, Model KM2P, Ratio 2.62:1

[never monday]

yes it sounds overloaded. I'd question the shape of the prop more than anything. Th3 14x8 is close enough that it should work better than it is.