Help with formula 242ls with 509 prop problems
 

Hi, I have a 88 formula 242ls. It has a fresh built 509 mag mpi. Couple little goodies (cam roller valve train etc) I'm having problems with finding a prop. I see these other guys with this boat and motor combo running in the mid 60s.

First prop I tried

23p mirage plus. Could over spin and blow it off

23p 4 blade Merc evolution, could spin to 5100rpm and see about 58mph

25p Mercruiser stainless 3 blade. Could only spin to 4800rpm, forgot to check speed

Now I have a 23 mirage on there (which is what everybody recommends for that boat) and it runs good with it but I can get on plane and do the initial trim up up and put it to 5100rpm seeing about 56mph.. The stock formula 242 with 454 runs that speed..

If I put all those numbers in for the 23 mirage on the slip calculator, it says I'm getting 23% slip..

Any help would be awesome, thanks

I had a 1990 242LS a while back. With the stock 454 (365HP) I ran 58 with a Mirage (non plus) 23P. I built a 620HP 496 and went to a 27P Mirage Plus and ran 71 at 5100 RPM.

That's what I'm saying. I'm not getting it

And that's what I have on there is a 23 non plus. Think the prop could be worn out? It run smooths and no dings, clean looking prop

Anybody?

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Make sure you have enough timing in it . Sounds like a power problem, Good luck!!!

But would it be a power problem if I can spin it all the way up to 5200rpm?

Yes , a motor can still turn up full rpm without making power. If your motor made 250 hp on the dyno , you could get it to spin 6000 rpm if you keep backing down on pitch . Check timing , throttle opening , ect.

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