Compression on 1989 Johnson 88 spl?

[PheasantsForever]

Does anyone know what factory compression would have been on a new 1989 Johnson 88 Spl?
Thanks

 

[Chinewalker]

Nothing was ever published, but a good rule of thumb is 100psi or better. The bigger thing to watch for is how even they are. You want no more than 10% variance between high and low readings.

 

[PheasantsForever]

I have compression readings of:
Top Left 119
Bottom Left 119
Top Right 120
Bottom Right 120

I talked with a local marine mechanic and he said those were low numbers, and that it should be closer to 150 for this motor.... Can anyone verify or dispute this claim?

 

[ondarvr]

Find a different mechanic. 120 is typical and good.

 

[PheasantsForever]

Thanks,
I am having problems with the boat not idling high enough. Stalling when put in gear. He was trying to tell me that compression was my issue. That I did not believe, but I am still wondering what my problem is.

 

[ondarvr]

Idle set too low, dirty carbs, weak spark.

 

[interalian]

I get 125-130 (cold) on my rebuilt 140. Your compression is fine.

You could prove dirty carbs by doing a cylinder drop test at idle, although the idle jets contribute a lot to low speed running, well above idle speed.

Remove throttle cable and set idle at dockside in water to about 700 using the idle screw. If running on muffs, set to 1000-1100 to allow for backpressure difference in exhaust. Adjust and re-fit the throttle cable so it just pulls the throttle to the idle stop (adjust trunnion nut as needed).