Repowering a 25D

[Ray Worthington]

Has anyone repowered a CD 25D? The 1GM (6 1/2 hp) in my 1982 does well to push it at 3 1/2 knots at full RPMs. I have heard that down-sizing the prop would help but that doesn't seem to be the real solution to me. Only more horsepower is my answer at present.



acw@thebest.net

[SteveZ]

My 1GM will push my 25D at hull speed (5.8 kts)in a reasonable chop. I have gotten around 4 kts average speed motoring directly into 25-30 mph winds and fairly nasty waves. To evaluate your propellor, check the Yanmar owners manual for what full rpm should be and compare this to the rpm you are experiencing. I would guess that your propellor is incorrect (size or pitch).

[Charles Curtis]

Has anyone repowered a CD 25D? The 1GM (6 1/2 hp) in my 1982 does well to push it at 3 1/2 knots at full RPMs. I have heard that down-sizing the prop would help but that doesn't seem to be the real solution to me. Only more horsepower is my answer at present.

I agree with Steve Z. I get much better perfomance from my 1982 1GM as should you. Your problem can probably be rectified without the considerable expense of repowering. 25D REVENGE #33



ccurtis@csra.com

[john vigor]

Ray, my 1GM gives my 25D full hull speed (5.8 knots) in a calm, 4 knots in a chop and headwind. If you're getting only 3 1/2 knots at about 3,400 rpm with a reasonably clean bottom, either your reduction gear is wrong (unlikely) or your prop is incorrectly sized (more likely). Or (even less likely, but you never know) your prop has lost a blade.
Your prop should be 12 inches in diameter by about 8 or 9 inches in pitch. It sounds as if you have a much smaller diameter and/or finer pitch. A good prop shop can change the pitch for you, up to about 2 inches or so (and maybe more, depending on the prop metal and construction) for a reasonable price. My local shop would charge under $50. But if the diameter is too small, you'll need to buy a new prop: three-bladed, bronze, right-handed, 12 x 9.

John Vigor
CD25D "Jabula"



jvig@whidbey.net

[Bob]

Have you checked your prop for barnacles? If your engine is smoking, you may need to change the filters or have the injector checked. Another common problem is a clogged mixing elbow.

Has anyone repowered a CD 25D? The 1GM (6 1/2 hp) in my 1982 does well to push it at 3 1/2 knots at full RPMs. I have heard that down-sizing the prop would help but that doesn't seem to be the real solution to me. Only more horsepower is my answer at present.

bobmcreynolds@hotmail.com