Going from aluminum to SS

[BLinindoll]

SS props are at some great prices here on iBoats so I'm gonna pick one up. I'm going from a 14.25" x 21p aluminum to SS. That size in aluminum is perfect. What should I go with for SS as far as size and pitch? A 14.25" x 23p Michigan Rapture is $205. How would that size act?

 

[steelespike]

Re: Going from aluminum to SS

Sounds like you are running an I/O.Without your present rpm and speed no way to know how the prop will act or what prop to choose.Also need boat size type and weight and what you want to accomplish.
Also going from al to ss can be tricky.Depending on what style prop.
it may lower rpm but increase speed other styles may increase rpm and speed.Give us the specs and perhaps the experts can make some suggestions.

 

[Randybeall]

Re: Going from aluminum to SS

What steelspike says is very important. Your initial suggestion is opposite what would normally work out going from alu to ss. The ss is more rigid and stronger in all aspects. This means a thinner blade with less drag, it also means the manufacturer can make a cup or taper pitch blade which moves water more efficently in the same pitch. Result, more load on the engine and lower rpm. That means you will likely go down in pitch on an engine which has the perfect alumnium prop on it. While this seems counter productive it gets you stronger hole shot and midrange while maintaining top speed and cutting fuel use through lower drag. Put down everything you can about boat performance now and experienced experts will give you guidance.

 

[BLinindoll]

Re: Going from aluminum to SS

It is an 88 21' Four Winns 200 Horizon with an OMC 4.3L 4V. I can hit about 42-44mph (on gauge, no gps) at about 4500-4600 RPMs WOT. The current prop is an aluminum 14.25" x 21 pitch. It has a decent hole shot. I plan on pulling a tube and possibly a skiier once in a while, but like to go fast too. I just ordered a SST 14.25" x 21 pitch on ebay for $150. Was this a good choice?

 

[steelespike]

Re: Going from aluminum to SS

If I was ordering a prop without definitive expert info from specs I would be ordering something in the same pitch.Keep in mind that depending on the design it could raise rpm and speed.

 

[Randybeall]

Re: Going from aluminum to SS

I would say that you have the best possible chance by matching what came off. The ss will put more load on the engine and hopefully bring the results you want.