1990 Johnson 175 VRO compression problems

[derekamundsen]

i have recently bought a 1990 johnson 175 VRO. on one side im reading about 50psi and the other has about 75psi. no problems starting the engine and putting it in gear. any help on why my compression would vary so much or any other information would help greatly. thanks


what would be the oil to gas ratio for this engine?

 

[Dhadley]

Re: 1990 Johnson 175 VRO compression problems

That's a 50:1 motor, a quart of oil to 12 gallons of fresh 87 octane.

There may be several reasons for the numbers but it's a good sign that each side is even although a little on the low side. If there was any real bad damage it wouldn't idle well.

Let's make sure the heads are a matching set. The casting numbers should be in order with the port head one number lower than the starboard head. It may have low compression heads and / or gaskets. The motor may be turning over a bit slow or not enough times. Then there are gauge differences.

In any case start with a good decarb job using BRP's Engine Tune. Follow the directions on the can closely. Let us know how it turns out. We'll go from there.

 

[derekamundsen]

Re: 1990 Johnson 175 VRO compression problems

Thanks for the info. The gas i mixed and put in the tank is 50:1 but its 97 any problems with that? I will check today and make sure that both of the heads are a matching set. I did some futher troubleshooting this past weekend and found that one of my sparkplugs had a very weak reading almost none at all. so im currently looking for a new coil pack. I think that would be contributing some to my rough idle and probably make it even easier to start..reply back with any info that you feel would help thanks.....