1964 johnson 18hp compression?

[Direct Hit]

This motor is hard to start, compression test showed 60 on top and 80 on bottom. I am assuming the motor is wore out. Found another powerhead with 90/90 compression, is that good for this motor? I gave it new points and condenser and caeb rebuild and did not help with anything, still hard to start It has elect. start.

 

[nwcove]

Re: 1964 johnson 18hp compression?

if your guage is right 90 psi isnt bad, but isnt good for that motor but it should still run ok. did you replace the coils and plug wires? did you do a "carb rebuild", or just blow it out and replace the gaskets?.

 

[Daviet]

Re: 1964 johnson 18hp compression?

Have you checked the spark at the plug wire ends, should jump a 1/4" air gap, and be bright blue. I know you said you replaced the points, maybe you have weak coils.

Might think about replacing the head gasket and take a look at the cylinders and pistons while you have the head off.

I have one similar, the compression runs 60-70, not the greatest but it runs pretty good.

 

[Direct Hit]

Re: 1964 johnson 18hp compression?

Havent replaced plug wires or coils,cleaned ceaned carb with new gaskets,pulled head off and dont see any wear or damage. It starts fairly easy when cold but after it warms up its really hard to restart. it has elect. start. Just lost here on this.

 

[Daviet]

Re: 1964 johnson 18hp compression?

Have you checked the spark when it it warm? A weak coil will show up when warm.

 

[kfa4303]

Re: 1964 johnson 18hp compression?

Hi Direct. Inability to start is usually an electrical/ignition issue. If the original coils have never been replaced, then they are alomost certainly bad. Not to worry, they're only about $20 each and you can get them right here at iboats. You may as well replace the points and condensers too. You can also get a "tune up" kit right here for about $20. Here's a great link that can walk you through an entire tune up from top to bottom. Holler if you get stuck.


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