motor project

**loop** · 09-01-2011

I posted this on S&F but this may be a better place to find this kind of info.
I plan on building an outboard this winter. By building I mean I will use an existing powerhead,probably an OMC v4 and mate it to a fabricated midsection similar to Jon Wrights Tinkertoy. All of this will be on top of a lower unit that I havent picked out yet. I want something smaller with a diameter than the stock v4 has.
I need to find the best gearcase possible that:
1. isnt too expensive,this is a low buck project
2. has parts readily available
3. has a relatively small bullet diameter,smaller than the stock v4
4. has a gear ratio in the 1.87 - 2.0 range give or take a little
5. can handle up to 150 horsepower for short bursts

I really dont care who makes the gearcase as long as it does what I need
the input splines wont matter since I will match them to whatever powerhead I end up with.I know this is quite a wish list but maybe someone out there knows of a good choice.
Durabilty isnt the number one concern as long as its not breaking parts everytime I step on the gas.
My goal for the project is for a 12"-15" shaft ,100-150 horsepower motor thats basically stock and weighs under 200#. It will be on my 13' Allison. My interest is in quick acceleration more than top speed.
If anyone has any tips on what would work I'd really appreciate it

**Aeroliner** · 09-01-2011

A couple choices might be available. The old Mercury Speedmaster 1 or 2. Parts are a little hard to find but this might work for your application. Another option could be found from the OMC racing applications. We are using a 45 SST lower unit on our 75-H MOD engine.

Alan

**largecar91** · 09-01-2011

I agree a super speedmaster or a Chrysler speedie but if you have to have a 1.87 - 2.0 gear ratio, that would rule these out.

**loop** · 09-01-2011

I probably should have pointed out that shiftable would be a plus but not a must.

I was thinking more like a stock type lower just because parts and props might be easier to come by,even if I have to do some adapting. Seems like theres plenty of old SE / EP / SST 60 props around.

Aeroliner- do you think the 45ss ower will handle that much power?

Largecar - My thoughts on the gear ratio was mostly to help with prop selection.
The Chrysler or Merc speedies would be cool. Sad thing is I had a Chrysler racer at one time..

thanks for your ideas and keep em coming!

**Aeroliner** · 09-01-2011

Look on this page for the 6 cylinder MOD engine. It has the 45 SST lower unit. The folks are also using this on the OMC Super E engines which are making a bit over 100HP. If your not to hard on it I think it should give you good service.

http://www.boatracingfacts.com/forum...t=6393&page=46

Alan