Anyway to run a prop from a 4-1/4 gearcase on a 4-3/4 gearcase?

[Chris1956]

I have a nice 21P Rapture that I bought for my Merc IL6. The IL6 blew up, and now I have a Merc 135HPV6, which has the 4-3/4 gearcase. Is there some sort of adaptor I can get to use the Rapture? I tried it w/o an adaptor and it was like driving a car with a slipping clutch....

 

[ufm82]

Re: Anyway to run a prop from a 4-1/4 gearcase on a 4-3/4 gearcase?

The are "cav-rings" that can be installed on the barrel of the prop that match up to the hub of the LU to decrease that gap. I've seen them on Merc Trophy props when being used on bassboats. (Trophy is a small barrel prop). This helps keep the exhaust from escaping around the prop as opposed to through it. They are typically brass. Ask a prop shop about them.

 

[Texasmark]

Re: Anyway to run a prop from a 4-1/4 gearcase on a 4-3/4 gearcase?

Why don't you run it then determine if you have a problem. There are lots of prop designs and some have a very narrow hub and the exhaust gasses pass over this hub with no problem....I think Cleaver Props run like this....these are the bad arse props on very fast, high performance boats that run over 65 mph.

On the flip side of this I have run a large gearbox prop on my small gearbox engine with no problems.

HTH,
Mark

 

[Chris1956]

Re: Anyway to run a prop from a 4-1/4 gearcase on a 4-3/4 gearcase?

Mark, I have run it. I expected much better performance than I observed, as I know about the cleaver props. I could hit 5500 RPM and only be moving at 30MPH, instead of the usual 50+ MPH, with the larger hub prop.