Mercruiser 120 I/O prop

[dozerII]

I just purchased a 72 Starcraft 18' SS with a Mercruiser 120 I/O the prop that is on it is in very bad condition, one blade is bent backward quite a bit and the other two are dinged up. The numbers on the prop are 48-79576A-4 21 P Acording to a search in the Iboats prop section it is a 15.25 X 21 p prop. Is this a good place to start, The only Hustler listed is 14.25 X 21p and there is a Michigan listed as 15 X 21P. I live in a remote area so I have to purchase these so I don't want to have to buy to many. Where should I start?
Thanks for any help.
Glen

 

[steelespike]

Re: Mercruiser 120 I/O prop

Don't worry about the diameter it will simply follow the design.
If you buy a prop from iboats on some the shipping is free.
Assuming the motor is healthy The 21 is a good place to start.
Experience has been that the Hustler props are unpredictable.

 

[dozerII]

Re: Mercruiser 120 I/O prop

Thanks for the reply Steelespike. The motor I am finding is in real good shape, Ijusr ran it on the muffs to warm it up and doa compression test and it was real good 135,155,155,150. Would the Michigan 15X 21 be a good choice?
Thanks again
Glen

 

[steelespike]

Re: Mercruiser 120 I/O prop

Nothing that I know of against a Michigan prop.

 

[Rick-]

Re: Mercruiser 120 I/O prop

I have a 85 Cheetah 17' with the mercruiser 120 I/O. My prop is a 14.5 X 17 Michigan. I have only owned this boat a few months and this is what came on it. It doesn't have the top end like i want but out of the hole it pulls very well.

 

[180shabah]

Re: Mercruiser 120 I/O prop

Kinda hard to make suggestions on a new prop without a baseline. Anyway to borrow a prop or two before buying one???

 

[usskydvr]

Re: Mercruiser 120 I/O prop

I know your current prop is bent up a bit, but what kind of WOT RPM are you turning with the boat normally loaded? Generally for your boat/engine I would say 21 for best speed, 19 for all around , 17 for waterskiing. Of course loading (and high altitude) can change all that.

 

[dozerII]

Re: Mercruiser 120 I/O prop

I'm sorry I don't have any numbers yet for a base line. When we took the boat for a test ride I didn't think to look at the tach and the speedo isn't working. Once I get it in the water here I can get these #'s. Th prop that was on it is in such bad shape I don't want to run it, one of the blades is bent back at least an inch and the rest are all chewd up. I have no place around to borrow props, so I just ordered one from Iboats in the same size as the one I have, as a starrting point. Once I have the numbers I will post them.
Thanks everyone for the help.
Glen

 

[180shabah]

Re: Mercruiser 120 I/O prop

Which prop did you get?

 

[dozerII]

Re: Mercruiser 120 I/O prop

180shabah, I ordered a Solas Amita 3 Blade 15.3 X 21 from Iboats
Glen

 

[180shabah]

Re: Mercruiser 120 I/O prop

cool, guess we'll see how it does....