1973 Merc 500 Compression Readings

[mbnjagn]

Hi All.

I just did a compression check after having some issues with idle and acceleration and a carburetor rebuild and this is what I found.

Cylinders 1 through 3 are 126 lbs and cylinder 4 is at 108 lbs.

Is there something starting to go wrong here? It only has about 25 hours since the fresh rebuild last year. I run the synthetic blend oil with a little Mercury decarb in each tank of gas.

Thanks.

 

[Dunaruna]

Re: 1973 Merc 500 Compression Readings

Yes, that is a problem. I would suggest you redo the comp test with a freshly recharged battery and start from #4 ( a weakening batt can give false readings).

If the comp readings are valid, time to revisit the shop that rebuilt it.