propell`s and speed
 

I have a scarab III 34` with twin carburated 502`s
510 Hp 5700 o/min and 540 torqe . TRS drives. what is the posible speed for this boat with the best propell??
4 or 3 blade and pitch ??. To day I have 3 blade and 21
Speed 60 knots:

jhyt

first .....that is a HEAVY boat!
Second......what RPM's are you turning at full speed? By the numbers you posted you make it sound like the engine is makeing its numbers at 5700rpm? are you running at that rpm on the water?
The 21p Prop seems a tad small .....i would try a 23 mirage. They seem to be the best prop for most applications on our scarabs. who knows you may actually need a bigger one with the power you are running.
My 30' ScarabII has 25's on it but they are a tad big. I'm turning 4800rpm right now and would like it to be closer to 5200 so i may have them pitched down to a 24.
I had 23's on before and was hitting my rev limiters so i found a great deal on two used props and took em......
I think generally you get about 200/300rpm higher for every pitch you drop and the other way araound for raiseing the pitch. It all comes down to trial and error for most boats cause they all react differently. Good luck :D

I am looking at a '88 scarabII. What kind of deadrise does this model have? Any history on these boats anywhere I can pull up?
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