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In article ,
says...

Gudmundur wrote:
Hi all,

The number is SSO-515-II-C and it is supposed to be a Michigan Wheel.

I tried the Michigan website, no luck.

Here is what I do know, I have an OMC 391198 13.75 X 15 aluminum
and the engine ran exactly 5000rpm w.o.t.
This Michigan stainless prop was in a box marked 13.75 X 15 stainless.
When I installed this stainless prop, my w.o.t. went to 6000rpm. That
makes no sense at all!! I would say the prop behaves like a 13 pitch
or even an 11 pitch. The boat holeshots like a rocket, and although
I don't have a speedometer, the boat does seem a tiny bit slower at
the original 5000rpm line.

This prop is about 10 years old dealer stock. Did someone put the wrong
prop in the box?? It really does look very much like 13.75 X 15 from
all I can measure. What is going on here?

Thanks!

Describe your boat. I have a 1975 Johnson 50hp w/ a 15" prop that spins
6000, & jumps out of the water on a 15' Feathercraft.

I'm thinking perhaps your aluminum prop might be faulty, or has been
re-pitched, and/or cupped.

Rob

70hp Evinrude 20" 3cyl 2stk 1981 on a FourWinns 15ft Catalina tri-hull.
It is similar to a Horizon model, but older, heavier, and kind of a
wide-glide. Being a tri-hull it is unusually wide for it's length. Rated
as six passenger and 100hp max. It creates a large wake up to about
12 knots and runs in the displacement mode, above 15 knots it planes out
real well, picks up about another 10 knots while reaching full plane
and proper trim. The GPS seems to show 25mph with the aluminum prop,
and 23mph with the stainless prop, both readings taken with the engine
at 5000rpm. Redline is 5500 for this motor.