I have a 1979 ArrowGlass 17 1/2 foot modified tri-hull with the original 115 hp Evinrude Outboard motor. I recently lost my prop to a hungry lake becuase of an aged cotter pin. I'm using my spare prop.
What I don't know:
The diameter/pitch of the current prop cause she's in winter storage.
The max RPMs cause the tachometer is broken
What I do know:
The spare prop does not pull skiers half as good as the lost prop.
I've read that the max RPMs are 4500 - 5500 and that the engine is rated at 5000.
I also read about someone with a 1979 115hp Evinrude that had a 19 pitch prop and was maxing at 5500 RPMs.
She starts to purr right around 30 mph.
What you should know:
I refurbished the boat with my dad a few years ago, so I don't know hardly anything about boats. My dad thinks the original prop was 14 x 7 (which doesn't make sense to me considering the things I've read...maybe it was 14 x 17). I mainly use the boat for skiing and tubing, so I want something that gets the skier out of the water quick and doesn't stress my engine while running about 25 - 30 mph.
I'm thinking of getting a 3 blade aluminum prop with a 13 - 14 diameter and a 17 - 19 pitch. Am I completely off base?
Welcome, You Should read the stickies at the top of ther page.
You really shouldn't make any prop changes without a tach.
A tinytach is reasonable and easy to install.One for your motor will fit any 4 cylinder 2 stroke.
That said a 17" pitch is in the ball park.However if it lets it over rev or causes it to lug you may end up with premature repair problems and poor performance.