1957 Ev 7.5 rpm info ???

[64osby]

I was given a box that contained all the parts of a 1957 evinrude (7522-12322) except the power head. I'm trying to figure out the specs for the RPMs this engine would have had, Idle and Max RPM's.

I am looking to see if I could repower this lower end with a 5HP Briggs Quantum XM (12F802 / 2017E1) that is on a non operating power washer. The Idle rpm of the B/S is listed as 1750, the HP is calculated at 3600 RPM 5 HP. Engine runs great

I'm trying to see if a direct coupler would work or if it would be best to use gears or belts to raise or lower the operating RPMs.

I think it would be fun to convert this with a 4 stroke air cooled engine and put it on our 12' row boat.

Any input would be great, Thanks

 

[64osby]

Re: 1957 Ev 7.5 rpm info ???

Bump, Anyone out here happen to know RPM's Help

 

[1kruzer1]

Re: 1957 Ev 7.5 rpm info ???

Interesting project. The original powerhead would have run 4000 to 4500 RPM wide open. Your problem is going to be getting the Briggs to run slow enough to shift the motor, as 1750 is too high and you may tear up the clutch dog and/or gears in shifting between forward-neutral-reverse. The original powerhead would idle smoothly all the way down to 600 RPM or even lower, however, it didn't need to be idled down all the way in order to shift. Anything below maybe 1200 would have been fine for shifting. If you could shave a few more hundred RPM off the idle speed of the Briggs you'd probably be ok. That engine has a governer so no worries about over-revving it on the top end, but if you do anything with gear reductions to slow down the coupling to the lower unit you won't have much top speed left, as you'll already be running at least 400RPM below the original powerhead.
I'd say tweak with the Briggs to get it to idle slower, hopefully down to 1300-1400 or so, and hook it up and see what happens.
Good luck and have fun!

 

[64osby]

Re: 1957 Ev 7.5 rpm info ???

1kruzer1

Thanks for the info. Before I get going too far I'll look to see how slow the B/S can idle.

I know my wife will roll her eyes when I start this project, too many going now, but I'm thinking the kids will love it.