Alpha One prop question
 

A friend who used to own an Alpha One gave me a nearly new SS propeller that I don't know whether I want to use it or just keep it as a spare - some thoughts would be appreciated.

The current setup is a 3.0l Mercruiser Alpha One that has an 3 blade aluminum 14 1/4" 21p prop. At WOT I am getting 4800 RPM and 43 MPH (speedo). The prop that was given to me is 3 blade SS 14 5/8" 23p prop.

I realize that I will need to measure for the extra 1/2" of diameter. What would be the effect of this prop on my configuration? Is this an upgrade or just a inexpensive spare?

Thanks!

Re: Alpha One prop question
 

Well, if you could count on the engine to still hit 4800 RPM: About another 4 MPH on top end, and being (a bit?) slower out of the hole.

But the reality is that, since the engine will be asked to do more work per revolution, odds are you won't hit 4800 RPM WOT anymore and she may become more than just "a bit" slower out of the hole.

Only way to know for sure is to try it.

Depends on what you want and what actually happens when you try it.

You're welcome.

Jim

Re: Alpha One prop question
 

I am actually happy with my setup. Perhaps a bit more hole shot but that issue really went away with the addition of the trim tabs. I have wanted a spare on board for awhile. My question remains the same - what would the effect of the larger prop and the 2p increase in pitch be on this configuration? More RPM, less RPM, etc.?

Re: Alpha One prop question
 

I believe I answered that. Did you not read what I wrote?

Jim

Re: Alpha One prop question
 

I did miss the first two lines Jim - many apologies. Your answer is exactly what I was looking for, thanks!

Re: Alpha One prop question
 

No worries :). You're welcome.

Btw: I'd note that swapping the prop is exceedingly trivial. When we hit something in on the bottom last season and spun ours, we limped over to a dock, tied off, ran down to the local West Marine for a prop, hub kit and wrench, and I changed it in the water, while hanging over the back with The Admiral sitting on my legs to keep me on the boat :D

http://www.linxnet.com/misc/pwrboat/...ny_pos2-2.jpeg

Jim

Re: Alpha One prop question
 

Your rpms at WOT will drop by about 400 and you will have much more difficulty getting out of the hole. Your configuration is nearly perfect so i wouldn't change it. Keep the SS for a spare or unload it on someone else.

Re: Alpha One prop question
 

Mikey - Thanks! I think that I will keep it as a spare until I find someone that can take advantage of it. I tend to doubt that any sort of prop would have a significant effect on my small motor. I often think that I would like a larger boat but giving up the fuel economy of this boat would be difficult. At 3000 - 3500 RPM's the 3L just sips fuel.

Re: Alpha One prop question
 

Funny - through a conversation with my wife my neighbor ended up buying the SS prop from me. The 3 blade Aluminum prop that I have appears to be the perfect setup although 1) I still want a spare on board and 2) the aluminum prop is fairly dinged up. As I stated previously I tend to doubt that a SS prop will have much performance gain on my small engine but I am leaning towards one from a resiliency perspective and making the existing aluminum prop a spare.

Any thoughts on a SS replacement for my setup? The current setup is a 3.0l Mercruiser Alpha One that has an 3 blade aluminum 14 1/4" 21p prop. At WOT I am getting 4800 RPM and 43 MPH (speedo). If I had a performance leaning it would be towards hole shot though I have little to complain about now.

Re: Alpha One prop question
 

I dunno how you are going to improve on those numbers. :) You could try a 21" - 4 blade SS to give just a little extra bite but your top end might drop 1-2 mph.