OMC to Johnson swap???

[justdoit]

Hello everybody, I recently bought a boat with a blown 1985 OMC Sea Drive outboard motor. This boat has that looong bracket at the tramson that puts the outboard like 2 feet away from the transom (not your typical 3" type) and I bought a 1972 Johnson to replace it but the SWIVEL bracket is NOT compatible. The OMC mounts with 4 bolts and the Johnson has only 2 bolts and they don't even lineup!!! How can I use this motor for this boat? Do I have to get an OMC motor to make it work? Help!!!

 

[WillyBWright]

Re: OMC to Johnson swap???

You can bolt a jackplate to the transom and hang the outboard on that if the configuration will allow the motor to tilt and not jam the powerhead into the transom. Otherwise there are outboard motor brackets that can be mounted to the transom and the outboard can be hung on that. The SeaDrive is an obsolete design.

 

[Dhadley]

Re: OMC to Johnson swap???

The transom design will tell you if you can use a jackplate or if you need a bracket. What you're looking for is clearance when tilting the motor so the hood doesn't hit the transom. A typical V4 set back is about 25" or so. A typical V6 is about 28" or so. If the top of the transom is low you'll get by with less. Since you're using a 20" motor (not usually a good idea on a bracket) you'll probably need more. If you were to use a 25" or 30" motor you could get by with a little less.

Another option which is very popular around here is to use a Porta Bracket. It's a sissiors type jackplate that has a lot of travel. It'll lift a 20" motor way up so you have lots of clearance.

To be honest, I'd rebuild the Sea Drive powerhead before using an old motor like the 1972. BTW -- we'll assume the 72 motor is a V4. It is held on with 4 bolts, not 2. Make darn sure you use all 4.