Can I swap out my 1972 Johnson 50HP for a 1978 85 hp Mercury. Need new cables?

[andrewbabich]

Can I swap out my 1972 Johnson 50HP for a 1978 Mercury. Do I need to buy new cables?

I have my buddies 85 hp 1978 Merc that I can put on my boat (which is rated up to 85hp).

How much work is swapping them out. Can a backyard mechanic do it in a weekend. Are the steering and throttle cables interchangable? Will I need to buy new parts?

 

[Chris1956]

Re: Can I swap out my 1972 Johnson 50HP for a 1978 85 hp Mercury. Need new cables?

The steering cable will be adaptable. The fuel line will be adaptable with a new motor fitting. The controls will not work, but the wiring may be adaptable. The mounting holes will be different. The fuel mix will be the same. Get the Merc Controls, and life will be easy....

If you run the old cable and pully steering, that motor may be a bit too powerful for it. I ran a merc 85HP on a 16 footer with cable and pully steering, w/o incident, but I would think caution is in order.

 

[andrewbabich]

Re: Can I swap out my 1972 Johnson 50HP for a 1978 85 hp Mercury. Need new cables?

How heavy are these motors. Can a couple of guys move them or do you need a lift of some sort.

Will I need to make new mounting holes?

I think it may be easier to fix the beater lobster boat with the 85 hp motor then swap motors.

 

[Chris1956]

Re: Can I swap out my 1972 Johnson 50HP for a 1978 85 hp Mercury. Need new cables?

That Merc 85HP motor is liftable by two guys. It is about 225LBS, I would think. Mounting holes will likely be different. Seal the old ones with silicone, and seal the new transom bolts and holes with the same. Swapping should take an hour or so.....