1977 175HP low compression 1 cylinder

[kmaxwell]

Looking to see if I'm on the right track. My 175 has 120 pounds of compression on 5 cylinders and almost none on 1. I fogged the engine at the end of season. It fired right up this spring and sounds good, no missing and idles nicely. Is it possible that a ring has stuck? Would it be worth the risk of using a "ring free" oil product and run the engine to see if this corrects it? Or am I risking major damage? When I did the compression test it I had nothing. I tached the engine to 1500rpm and the tester jumped to 60 pounds. I left the tester on for 15 minutes and it did not drop pressure. Any thoughts or suggestions would be great. I am currently suffering from compression depression.

 

[jonesg]

Re: 1977 175HP low compression 1 cylinder

foggin oil stuck the ring?
Spray some seafoam in it and let it soak half an hour.

 

[tashasdaddy]

Re: 1977 175HP low compression 1 cylinder

the compression tester has a check value and will not drop the reading. so you got a false test. you can try a decarb, and see if it helps.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[floffshore]

Re: 1977 175HP low compression 1 cylinder

if youre somewhat mechanically inclined, you can just order a new head gasket (about $15-$20) and pull the head off on the side you think has issues. it's really easy to do and it will tell you for sure. it took me about an hour to pull it off, inspect, and reinstall. and i took my time!

if you have scoring, streaks, or gouges along the cylinder walls, you know that cylinder is toasted for sure.

 

[kenmyfam]

Re: 1977 175HP low compression 1 cylinder

Compression tester will fix at the highest reading it gets to until you release that valve. It may well sound and appear O.K. on the muffs but as soon as it has a load on it it could well be a different story. Could be as simple as a head gasket. If you are willing to invest in one then you can have a good look at the cylinder wall while you are in there. How does the plug on that cylinder look compared to the rest ??
If all looks well within and the head gasket is replaced and torqued, give it another compression test then try the decarb.
Good Luck and keep us all posted.
Photos are always a big help for everyone to diagnose from as well as symptoms.