Prop size vs RPM - speed???

getrdunn · 03-27-2009, 10:00 PM

With a twin application if you ran 27 pitch mirages @ 5200 RPM = What speed??? Approx.

(32' light layup 6500 pds) flat/chop water.

John

Griff · 03-28-2009, 03:06 AM

That would depend on the drive ratio and approximate prop slip %

http://go-fast.com/Prop_Slip_Calculator.htm

bbladesprops · 03-30-2009, 06:56 PM

12% slip gives you 78 mph.

B

getrdunn · 03-31-2009, 09:07 PM

Quote:

Originally Posted by daredevil

What ratio ????

I realized I forgot to mention the ratio with the first thread and then I figured it out from the website mentioned. I use to be so good at this when I was running a lot more. I could always tell when somebody was full of s**t when they said how fast they were going when I knew what props/rpm/'s they were at.

anyhow I am pretty certain the merc. trans / trs set up is 1.5??? the boat was running 23's with stock 330's at 4600 rpm at near or around 62 - 64 mph.

I not real familiar with the trs drives and trans. I've always had bravos in the past.

any help with the said set up..

bbladesprops · 04-01-2009, 10:39 AM

That would be under 6%. Probably too good to be true.

Speedo or GPS?

getrdunn · 04-01-2009, 09:03 PM

Quote:

Originally Posted by bbladesprops

That would be under 6%. Probably too good to be true.

Speedo or GPS?

speedo, sorry about that and not gafrig either.

is there a common ratio for the old trs drive and merc trans. this is a 1978 boat.

getrdunn · 04-03-2009, 10:49 AM

Need a single screw I guess.