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barefooterh2o
06-22-2009, 02:35 PM
I have the original 13x13 3 blade OJ prop on a 2007 Outback. RPM's are 200 higher than mph for barefooting speeds of 38 mph (4000 rpms to 38 mph and broader range at 43 mph for 1 foots). On my 05 Malibu it's rpms are same as mph with the 13x13 prop. So 38 mph is 3800 rpms. The Moomba sounds like it's screaming at 38 to 43 mph. Any recommendations on different prop for barefooting? There is no nicks in the prop and it has been like this since the boat was purchased new.

Thanks.

maxpower220
06-22-2009, 05:10 PM
It's pretty common for the OB to be 2 mph off of RPM, that is the way my boat is also. You should call Acme or OJ for a recommendation for a prop.

Hoopskier
06-23-2009, 12:42 AM
I would recommend calling the prop people for the best answer.

I do know that as far as prop solection that at wide open throttle you want to be at the very top of the rpm range. This way you are using the most of you engine. The steeper the pitch the more load you create on the engine. If the engine can turn the steeper pitch the faster you will go. If the engine can't turn it to the top rpm you will be going slower you go (as compared to the prop with less pitch). I hope you follow what i'm trying to say.

I have an 03 OB with the 320 hp engine. I run 4600 rpm with the OJ legend 13x13 3 blade prop. I don't know what speed it is. I never figured it out as i know the speedos are off.

barefooterh2o
06-23-2009, 05:02 PM
I use a GPS twice a year to adjust the mph on the speedos. It's different in cold water than warm water. About a mile and a half to 2 miles off from 30's degree water to 70 degree. And if you didn't catch it, we barefoot ski until the lakes freezes over. Last year we skied when only a 1/2 mile stretch was not iced over (out of 7 miles of lake).

Sharpie647
06-23-2009, 05:05 PM
I use a GPS twice a year to adjust the mph on the speedos. It's different in cold water than warm water. About a mile and a half to 2 miles off from 30's degree water to 70 degree. And if you didn't catch it, we barefoot ski until the lakes freezes over. Last year we skied when only a 1/2 mile stretch was not iced over (out of 7 miles of lake).

THATS JUST CRAZY!!! Good for you. I don't think you'll see me out there.

snowboardcorey
06-23-2009, 07:45 PM
Not sure but I think the Bu has a little less wetted surface area which is likely why you are seeing the difference in rpm/speed. Give the boys at Acme a call, I know most of the three event clubs around here running MC's with a 310 or 350 hp engine and 1:1 are running the 13x12 Acme with 0.08 cup, not sure if thats what the footers are running or not.