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  Can you turn a 12 5/8 x21 on a 115 Yamaha?

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Author Topic:   Can you turn a 12 5/8 x21 on a 115 Yamaha?
eaglet1122 posted 10-13-2002 01:18 AM ET (US)   Profile for eaglet1122   Send Email to eaglet1122  
I have a 1996 17 outrage with a 96 115 Yamaha. Current prop is 13x17. WOT now =6000 rpms. I was looking at a aluminum prop with a 21" pitch. Is this to much for a 115? I will have no less the 2-3 full size adults and 3/4 full tank [45 gal]90% of the time. I would like to pull a kneeboarder/tube. Shold I let this prop go and get a 19"? Any and all info is greatly appreciated. Thanks, Stan
John from Madison CT posted 10-13-2002 08:02 AM ET (US)     Profile for John from Madison CT  Send Email to John from Madison CT     

You are turning a little too high RPM's with that Prop, but not really all that bad. Nearly all OB mechanics will say to be in the higher RPM range rather than lower.
Personally, I would get a 19" prop. You will still be in the top RPM range as you should drop around 400RPM's.
You will see a Top end speed increase IMO.

Giddie Up and go get 'em.

John from Madison, CT

Clark Roberts posted 10-13-2002 08:17 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
John's advice is on the mark... suggest you borrow a 19" and make a test run before buying! Happy Whalin'.. Clark.. SCN
Sal DiMercurio posted 10-13-2002 11:17 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
What is the recommended maximum rpm for that engine?
If i'm not mistaken, i think it's close to 5,500 rpms.
By going from a 17 pitch, to a 21 pitch, your going to drop from 6,000 rpms, to 5,200 rpms.
For the best performance, [ & the engine will live longer ] prop it for the highest recommended rpm.
The reason for this is, if you prop it for the lower end of the rpm scale, & you put any type of load at all on the boat, your going to be lugging that engine/
It would be like towing a 22 ft boat behind a stick shift pickup, going up a steep hill in 5th gear, & not down shifting in order for your rpms to run at a normal rate, like going 30 mph up the hill, in 4th or 5th gear, with your foot to the floor.
Thats a sure way to kill an engine very, very fast.
eaglet1122 posted 10-13-2002 01:47 PM ET (US)     Profile for eaglet1122  Send Email to eaglet1122     
Thanks, I will try and find a 19". are there any good placed to find used props? Thanks, Stan
DanT posted 10-13-2002 04:05 PM ET (US)     Profile for DanT  Send Email to DanT     
Stan, if your current 13X17 prop is stainless steel, would you be interested in trading it for a 13X19 SS prop?
eaglet1122 posted 10-13-2002 05:22 PM ET (US)     Profile for eaglet1122  Send Email to eaglet1122     
You have a working email? Thanks so much, Stan
eaglet1122 posted 10-13-2002 07:59 PM ET (US)     Profile for eaglet1122  Send Email to eaglet1122     
If you are intrested in selling a 13x 19 or anyone else for that matter please email me @ or Thanks, Stan

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