new prop for increased power on 4.3

[steele in sc]

Hey guys,

I have a 1988 SeaRay Seville 18.5 foot, 2100lb dry, bowrider. Stock it came with 175hp 4.3 v6. The alpha outdrive has a 1.84 ratio to it. I have increased the power to somewhere around 235hp with many modifications recently and now I overrev the 13.75 x 21 prop. I have tried 14x23 (1 of 3 blades slightly bent) and it still would rev to 5500rpm. Any suggestions? I kept the stock cam but used newer vortec heads, 4 barrel intake and carb, flat top pistons, on and on.

Any help would be greatly appreciated.

Thanks,
Greg

greg.steele@charter.net

 

[fossill]

Re: new prop for increased power on 4.3

Maybe a Merc High 5 prop in 23 pitch or higher would keep it from over reving.
Trouble is they are pricey.

 

[nofuss]

Re: new prop for increased power on 4.3

any hints on easy mods that could improve horse power on the 4.3 with out taking the engine out. I have a 4.3 merc vortex EFI trottle body injection and I am told i should be getting 190 HP from each engine, some more wont hurt

 

[Slip Away]

Re: new prop for increased power on 4.3

Try an Apollo 3 blade stainless 14.25 x 25 3 blade. Part# 345136, but will also not be cheap.

 

[180shabah]

Re: new prop for increased power on 4.3

steele - you need to either find a prop exchange dealer in your area, or borrow a prop or two from friends to establish a baseline.

OR - if you can provide WOT performance data with your old setup, there are a couple guys on here that do math and and get your REAL close.

OR - you could regear your drive to get back where you can use "normal" propellors.

fossil - the high fives are smaller diameter, so his WOT would be comparable to a 3 blade of the same pitch.

nofuss - you need to start a new thread, not hi-jack. Short answer though, there is no quick, easy, cheap power to be had for your setup.

 

[steele in sc]

Re: new prop for increased power on 4.3

When the original 4.3 motor was fresh, the engine spun 4600RPM wide open throttle and would go 51mph according to the speedometer with a 13.75 x 21 prop. Who should I contact about the math?

 

[steelespike]

Re: new prop for increased power on 4.3

If the 23s condition is suspect your rpm may not be as a 23 should be.You could have it repaired perhaps add some cup.You might get enough base line to tell if you can do it with a prop change.My guess is geares from a 228 hp might work of course I think thats an 8 but I'm not an I/O guy.