'88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

[Sorrento 25]

Would this be a decent propeller for this combo in my Sorrento 25 (1.47 ratio??).

 

[walleyehed]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

The large-blade Apollo is a real good, heavy-load prop...Now, with that being said, what prop do you have now and what RPM are you getting?
Are there any problems with the prop you have now? Anything you don't like, I should ask...

 

[Sorrento 25]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

Well it looks like about a 15.5 and it says 15 pitch but its in bad shape - nicks, corrosion, pitting, one blade seems to have no cup. It pulled 4400 RPM with a very nasty bottom - multiple heavy flaking layers of bottom paint that will all be gone by spring. No speedo though... I found a deal on this prop and am hoping the additional efficiency of the newer SS design and the light loads I'll usually carry will make it work well, and was hoping that maybe someone with a similar boat might be using a similar prop with success.

 

[walleyehed]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

What is max recommended RPM, and how did the prop perform in the begining?
I know we are going to gain some with a clean bottom but we need some data as to how it performed with the previous prop if possible.

 

[Sorrento 25]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

Its a new boat to me and I only had it out once to rinse the salt off. It came up on plane very quickly IMO so I thought I could get away with a little more pitch especially after considering the condition of this prop and the bottom. In spring I'll have GPS to evaluate it better but for now all I can do is guess. I think recommended RPM on a 7.4 is 4200 - 4600?

 

[walleyehed]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

The more a prop wears, the higher the RPM will be...considering we have some bottom fouling, it may even out. If we go to a 17P, I would recomend a test prop first because by my calculations, a good 15P in SS is going to be the best bet. The 17 may put you in the lower part of the RPM range, so a test prop would be best if you can get one to test...possibly a Mirage plus.

 

[Sorrento 25]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

Thanks I'll try to find one!

 

[Crownie2]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

I agree with Kenny - 17" may prove to be too much in a SS so see if you can try one at a Merc dealer - some do offer loaner props.

Also - Merc doesn't usually recommend a Mirage on an Alpha drive - but in your case it may work...

Bob

 

[walleyehed]

Re: '88 7.4/Alpha 5500 lbs. Apollo 15.5 x 17

We're talking a 7.4L here with-in the years they put the Alpha behind it. My Merc Quide says V6 to 500+ HP for the Mirage, and I've been using the Mirage on an Alpha for several years with no issues until I ran the Apollo, which is now mounted to the 350 powered Wellcraft.