outdrive ratio
 

Are there any know negatives to running a 1:35 vs the 1:5 on the 28?

i remember reading on here somewhere about this. it has to do with your prop. they talked about the desired prop being in the 23-24 pitch range being optimal for bow lift. if your there already with a 1.50 i wouldnt change. dont quote me on this tho. griff would have a good idea. he is pretty sharp with this stuff

I'm good with the theory and all I just didn't know if anyone was running the 1:35 and if there was any draw back in the performance on the 28 . I believe the prop shaft spins faster than the 1:5 therefore allowing a smaller prop. I don't believe I was going to have a problem running out of prop on my set up with the 1:5. I am a little concerned about diverting from the proven norm though.

If your concerned about diverting from the norm, it's to late for that one dude.. :bunnydance:

If you are below a 32" prop, then I would probably stay with the 1.50.
A 32" should be about a 90mph prop with a 1.50

LOL. You got me:silenced:

I was told by Imco that with all top speeds the same between the two ratio drives.( assume props were obviously changed to match equal top speed) that the 1:5 had a better "rolling torque". Basically the 1:5 would have slightly better acceleration.

Not sure why they say "rolling" when we are talking boats. It also seems slightly puzzling when you think about the gears and prop ratios as just a math formula and why there would be a difference in acceleration. I know with cars the rear end gear and the tire size can be changed to achieve the same results. I guess the prop speed and hydro action make the difference in slip or something. weird.:bong:

Any thoughts?

bblades would probably know the answer

I have 1.33 on number III's with 425hp and 15 3/8 x 26, I can only turn them to 4200 rpm. I am hoping for some more rpm with nickersons carb work? I was told that if I switched them to 1.50 my rpm would probably be about right but I don't know.

Good idea

If Torque is your friend then go 1.5. Generally I/O boats are always faster with 1.5 vs 1.35 or 1.33 if props are available and they are now up to 36" or more. Remember a smaller pitch prop spinning faster mandates each blade to travel through more water per mile therefore more hydrodynamic drag per mile will be less efficient as far as top speed goes. Endurance would be the only reason( other than true back to back test results) to use a lower ratio as that will not multiply the engine torque as much so there is less theoretical propshaft and bearing loading at the (output) propshaft. This seems to be why diesels (high torque) use 1.3 or lower ratios and 2 strokes(low torque) usually need roughly 2.0 ratios. So much for my 2 cents:daz: