OMC 120 repower

Considering repowering my pontoon to a modern outboard, currently powered by a 1975 OMC 120 stringer. Would be a relatively easy swap (compared to a v-hull), cut out the existing engine bay (basically an aluminum box) installing new crossmembers and installing a transom pod.

My question is, the OMC 120, how would that compare to an equivalent horsepower outboard? Do you get more of the horsepower to the prop with a modern outboard? I would assume also that the power-to-weight ratio would be better with an outboard?

Thoughts?

Thanks!
Stan

Ayuh,..... Horsepower is a mathamagical equation, that hasn't changed,....

120 hp is still 120 hp,....

I'd say ya need atleast a 120 hp outboard, or bigger,....

I appreciate your feedback and I guess I understand that horsepower is horsepower, but I would think that the way it is generated and delivered varies.

Is HP apples to apples when you start talking about gearing, powerbands, RPM's etc? I believe that WOT for the OMC 120 is around 4,500 RPM's, whereas I see many outboards are WOT at 5,500/6,000.

I guess another factor to consider is that you can't trim out an OMC stringer with a ball gear drive like with an outboard to get the best prop angle in the water. Not that I'm planing out my 24 foot pontoon much but depending on load distribution the nose can be pointed up somewhat.

A modern 400 lb 120 outboard would be propshaft power.----I do not believe the roughly 600 lb 120 sterndrive was rated at the prop.---------You might be surprized what a 90 outboard would do on that pontoon.-----Find a dealer in your area that sells / installs motors.