Johnson Super Seahorse 40hp (1965) BACKFIRE

[steveo555]

Hello again chaps. Fitted all new coils and ignition kit, leads etc all nice and clean. I have spark at last! Start her up and the starter has real trouble turning her over. Once he does, nothing. Do it again, nothing, couple more goes and Kaboom! huge backfire from exhaust, prop spins once water goes everywhere. Is my problem a simple timing issue? Also how easy is it to repair the thread on head cos the spark plug on the bottom cylinder just spins (an over zelous helper!)<br /><br />Cheers

 

[R.Johnson]

Re: Johnson Super Seahorse 40hp (1965) BACKFIRE

What did the flywheel key, and keyway look like? The cam that opens the points lifts up, and off the crankshaft. Did you have this off when working on the magneto? It is marked "UP". What did you set the points at? You will have to repair, or replace the cylinder head. You are probably loseing a lot of compression as is. You said you replaced the spark plug leads. Are you sure you don't have them turned around.

 

[Chinewalker]

Re: Johnson Super Seahorse 40hp (1965) BACKFIRE

I suspect the issue is much simpler than that. Sounds like a classic case of "got the wires on backwards". The FRONT coil fires the TOP cylinder...<br />- Scott

 

[itstippy]

Re: Johnson Super Seahorse 40hp (1965) BACKFIRE

Do not run it with a plug that "just spins". That is not what the OMC engineers designed for this motor.

 

[Paul Moir]

Re: Johnson Super Seahorse 40hp (1965) BACKFIRE

Ditto itstippy.<br />As for fixing it, it's pretty easy. Simply remove the head, install (or have installed) a 'heli-coil', and torque the head back on with a new head-gasket. Needless to say, a service manual is needed.<br />Some may tell you that you can install the heli-coil without removing the head. But not me. A good reliable engine is worth more than a $10 head gasket.

 

[rolmops]

Re: Johnson Super Seahorse 40hp (1965) BACKFIRE

Chinewalker usually hits the nail on the head so no comment there.As far as your "spinning" plug is concerned.You have to take the cylinder head off(no big deal)and stick a helicoil in the ruined thread.Just make sure to rethread the old thread nice and straight before inserting the helicoil.<br />You can get helicoils in most car part stores.Just bring your plug along and the people there will get you the right size and explain how to use them.They are not expensive at all.