rebuilding a 70hp johnsohn outboard?

[desertgoldhound]

I have just purchased a boat that has a 70hp Johnson outboard. I was told that the motor was no good. They said that piston #3 was bad. I will be picking the boat up in two weeks.

I would like to save this motor. I would like to rebuild the whole thing.

What tests would be good for identifying the problems it is having (I.E. Run a compression test)?

Can you bore the motor? What is the highest bore you would go?

Thanks in advance

 

[Dhadley]

Re: rebuilding a 70hp johnsohn outboard?

There are a couple of different versions of the 70, depending on what year it is. Both are very good motors. Both can be bored to .040 over. It'd have to very trashed to be unbuildable. If you can get the rig for what you consider the boat to be worth, go for it.

A compression test would be a good starting point, among other things (wouldn't hurt to check the gear oil etc). Then we'll probably get into pulling the head just to take a peek.

 

[desertgoldhound]

Re: rebuilding a 70hp johnsohn outboard?

Can any machine shop work on boat motors or do I have to find one that is for boat motors. The reason I am asking this is that I saw somewhere on the net that when you put your head bolts to tork it warps the hole and that you need to simulate the heads being on it during the boring process. Is there any truth behind this or is it someone’s Idea to make money?