115 johnson not releasing exhaust pressure

[Bonanza79]

I have a 1979 johnson that apperas to not be releasing the exhaust pressure properly it is building up inside the cylinder heads and not allowing the motor to crank properly. Does anyone know how the exhaust system works on these motors or what can be causing that problem.

 

[tx1961whaler]

Re: 115 johnson not releasing exhaust pressure

I really doubt that exhaust pressure is the problem. There are no valves or anything like a 4 stroke engine has. The exhaust comes out from around the prop directly from the cylinders' exhaust ports. There is a remote, very unlikely possibility that some critter has crawled into the exhaust from the prop and has built a nest up in there. But probably not.
The reason your motor turns over faster without spark plugs is because there is NO compression at all.

I'd continue troubleshooting the starting system (with a fully charged battery) using a voltmeter, and measuring the voltage (negative voltmeter lead directly on the negative battery terminal):

At the positive battery terminal (not cranking)
At the positive battery terminal (cranking)
At the battery side of the solenoid (cranking)
At the motor side of the solenoid (cranking)
At the starter lug (cranking)
At the connection to the engine block for the negative connection (cranking)

 

[Bonanza79]

Re: 115 johnson not releasing exhaust pressure

Thank you I will try that this morning