A friend is putting together some 540's for his 95 31 Scarab.
They should make around 575hp at the prop. He is wondering which ratio to go with.

Any suggestions ?

1.5 The only time you need to go with 1.36 is when a 30-36" prop is too small when used with 1.5 gears. I do not think he will be needing props that big.

It depends a lot on the boat too. My formula311 run much faster with 1.36 gears than with 1.5's. This allows you to run lower pitch props which are more efficient in theory. It doesnt apply to every boat. I know of some formulas that ran better with 1.78's so its not an easy decision. There is some debate that the 1.35 drive is stonger too but I dont want to start that argument again. I suppose the engines characteristics might have some effect too.

Damn Tom what kind of answer was that?
You know that I know that they know ya know

My guess would be to stick with the 1:50 with that power size combo

Swing a bigger prop slower until you run out of prop pitch. Thats what I have been told. 1.50 Ratio and 32's would be close.

Howabout having him run his, then try Johnnies, he's got the 1.36s he's running ?

..........Yeah, what Ray said.

jt

i ran a 1.36 on my old scarab and did not like it. stay with the 1.50. on my hustler the factory told me that the 1.50 was faster than the 1.36 .i guess more efficient

I also would like to stick with the 1.50 gears, BUT the larger the pitch in prop size the more STRAIN and STRESS it puts on your drives and everyone knows that this can lead to breakage. I may eventually switch to the 1.36's on my drives just to help keep the stress off the drives from my 540's. It's certainly food for thought!