what is the correct prop size?

[Frankiea87]

hey guys i have a 1988 sea ray sundancer 268 with a 454 merc and alpha one drive, i have a 4 blade (dont know the pitch) and my motor full throttle is around 5k rpm with speed 30mph, ive been speaking to people and they say to switch to a 3 blade and it will lower my full throttle rpm by 200rpm per every inch of pitch changed? also 4 blade ive heard gets you on plane faster and 3 blade will get you more top speed (so i haveto compromise on one or the other). so i figure hey once im on plane with a 3 blade (eventually) then i can gain my speed. anyone know a correct size prop i should have on this? thank you!

 

[blaster]

5,000 rpm's seems high. Might want to check the Wot range for that motor I think its 4,600 max. The pitch can be found stamped into the prop hub. If there is no pitch check the model number on google. I have seen a couple threads on your size boat actually gaining speed with a 4 blade which is not the norm. Seems mid 20's cruisers bebefit from the 4 blade. Is your prop aluminum or steel?

 

[Frankiea87]

Cant read the numbers..all corroded..alluminum prop