31 O'day Prop Size

[David C. Hirtle]

I'm looking for a little input from anyone with a 31 O'day (mine is an '86) with the Universal M-18, 14 hp motor. The prop I am currently turning is a 15x7.5x1. This has been been adjusted from a 15x9x1. When I purchased the boat I don't believe the prop was original.I continue to produce smoke @ the top end of the RPM scale. Injectors are fine, transmission is fine, fuel supply is fine. It is not overheating.I would appreciate the dimensions of your prop. Thanks!

 

[Rich J]

Smoke?

Dave,Is it just smoke, or do you have a black water discharge? especially under a load?Yes, your prop may be the wrong size, but lets look into another source, does your engine have a mixing elbow on the exhaust? most raw water cooled engines (diesel) use a water injection elbow on the exhaust. This I know, because I thought my problem was the prop, the fuel, injectors etc...what I found was the mixing elbow on my engine was clogged with soot, I cleaned it out and no more smoke and black water.I hope this was helpfullRichJ

 

[David C. Hirtle]

Good Morning Rich J. Thanks for the mail...I'll give it a look see. I just had the elboe off and it had some soot in it. I cleaned it...I have never had the manifold off....maybe...I have found from another source that other O'day 31's with the same engine configuration spin a 14x10 where I am spinning a 15x7.5. I'll dig deeper and see what else might be there.Thanks again.David