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.

Re: Alpha One prop question
 

Hi phlorida, I ran a 4 blade Mach Sterndriver prop on my old Searay 170 with the same power package. It was an 18 pitch. Hole shot was great. I could pull both my boys up on skis (took everything she had). Mach's not around anymore but Mercury offers some nice props as well as other companies.

Re: Alpha One prop question
 

OK, no more procrastination......I bent the crap out of my aluminum prop this weekend leaving a local restaurant. I ordered a SS prop from iBoats that is the identical configuration of my current prop which everyone seem to agree was perfect for the boat. (3 blade, 14 1/4" x 21p)

I had originally thought that I would have the aluminum prop reconditioned and keep it on the boat as a spare but now I am second guessing that. Beyond falling off, can much go wrong with a decent SS prop? Don't I really just need a spare hub on board?

Re: Alpha One prop question
 

Having a spare hub will help with the minor impacts but if you bang it hard off a rock you will damage the SS prop. I would keep a spare around, whether its repairing the damaged one or looking for a used 20 - 21" 4 blade.

Re: Alpha One prop question
 

I had a chance to run the boat today with the new prop and got completely unexpected results. The old prop was a Mercury aluminum 14 1/4" x 21p. The new prop is a SS Stiletto with exactly the same specs to I had anticipated similar performance. With the previous prop I was getting 44mph at 4800 RPM WOT. With the new prop I am getting 42mph at 4200 RPM WOT - disappointing to say the least. It was windy today so I really didn't get a chance to test it out much but so far I am ready to dump the SS prop. Any thoughts as to why the performance hit?

Re: Alpha One prop question
 

Unfortunately if you move to a SS prop you normally have to drop 1-2" pitch for the same performance, particularly on a 4cyl sterndrive cuz it just doesn't have the torque to push the stiffer prop at that size. There may also have been a slight difference in rake etc which had some effect. A 19" 3 blade Stiletto would likely have given you the same rpms & performance. See if you can do an exchange?


btw...heres some test results i saw on a guy with a SeaRay 180 and the 4.3 engine....

14.25 x 21 Black Max (Good all around prop)
14 x 23 Black Max (Big mistake, don't ask, LOL)
14 x 21 Aluminum Hustler (couldn't get over 4600 RPM and lost a little speed)
14 x 19 Aluminum Hustler (OK... I guess)
13.625 x 21 Stainless Vengeance (not too bad actually, only the 14.25 x 19 Stiletto was better)
14.25 x 21 Stiletto (a bit too big for me, take off suffered)
14.25 x 19 Stiletto (The very best of the whole group, in all categories)
14 x 20 Alpha 4 (not impressed at all)

Re: Alpha One prop question
 

I can get my money back for the 21P. Another question for you all please. There is a great deal on a new SS Stiletto 14 1/8" x 19P on my local Craigslist. I went over to look at it and balked as it doesn't use a rubber hub like the 21" did, it has a round solid brass insert where the square rubber hub was on the 21". Otherwise it looks flawless. Any thoughts?

It is stamped with 10319 M1419 which seems to align to a Stiletto Advantage II.

Re: Alpha One prop question
 

I'm not quite clear on the hub used but does it look like this one or like this one? If not then here's Iboat's hub kit page.

I'm assuming also that the prop is hubbed for a Mercruiser and not some other application? Just another thought though, the Advantage II is designed for engines of 135hp and up. The Advantage I is for engines of 70 - 140hp.

Re: Alpha One prop question
 

I'm running a Michigan Wheel 14x17 on my Diablo with the same power package as your boat. I had a 14x19 on it prior to eating a stick and damaging it.

My experience is that my 17p pops the boat out of the hole instantly. I nail the throttle 3/4 of the way and within a few seconds the boat is on plane and I can back off the throttle. RPM's max at around 4500 with a top speed of 38mph. I actually tested it out today and this was with my wife and a little under 1/2 tank of gas. My old prop only achieved around 42 mph ( I believe, but this was with passengers onboard.. more fuel, and I don't remember the RPM's I was running).

I plan on following your thread because I want to eventually buy another prop. I have my old one 14x19 which isn't in bad shape. I'm considering having it fixed and maybe repitched so seeing what you end up with may nfluence my decision.

Good luck,
Nick

Re: Alpha One prop question
 

It doesn't look like either of those - it really doesn't have a hub per se. On the back of the 21P there is an empty, squarish cavity where the hub drops in. On the 19P there is a round piece of brass with a hole through it for the prop shaft - it doesn't appear that it can be removed. On the front of the 21p you drop a piece into the hub that fits onto the spline. On the 19P that piece is an integral part of the prop and cannot be removed.

It is for a Mercruiser. The guy bought it for a 4.3L but sold the boat before using it. The 3.0L is 135HP so I guess that either would work?

Re: Alpha One prop question
 

I searched your part # and came up with this: 2008 Stiletto M1419 10319 Used -Excellent - AvidBoater.com

Which is odd, because I think the pictured prop has an OMC hub... :confused:

Re: Alpha One prop question
 

That looks like the same one except the one I am looking at has the Merc hub. It is also brand new and $100 which is why I am interested.

Re: Alpha One prop question
 

you might try the 23 pitch but have the prop punch pitched which will lower the leading edge pitch. should get out of the water the same if not better gain 2-4 mph will probably lower the rpms. however you can have your prop man check the cup and make sure it follows around the prop . this will give you your r's back as you will be able to trim the boat higher,.