1963 Starflite 75hp low compression Stuck Rings?

[heryrg2711]

hey Guys,
Just did a legit compression test and i'm getting low values, they are all about the same around 50-55psi.

I think the rings are bad because when i sprayed a bit of oil into one of the cylinders the compression went up to about 65psi.

Is there a safe fuel additive for outboard that could free up the rings? Anyone heard of Yamaha Ring Free? Any good?

Also three of the four spark plugs are very fouled up, very blackish, One plug is a bit better but still not as clean as i would like, running too rich?

Any ideas? I've done quite a bit of work on the motor already so if info is needed ask and you shall receive.

Thanks guys!

 

[jbjennings]

Re: 1963 Starflite 75hp low compression Stuck Rings?

hey Guys, Just did a legit compression test and i'm getting low values, they are all about the same around 50-55psi. I think the rings are bad because when i sprayed a bit of oil into one of the cylinders the compression went up to about 65psi. Is there a safe fuel additive for outboard that could free up the rings? Anyone heard of Yamaha Ring Free? Any good?Also three of the four spark plugs are very fouled up, very blackish, One plug is a bit better but still not as clean as i would like, running too rich? Any ideas? I've done quite a bit of work on the motor already so if info is needed ask and you shall receive.Will it run; if so, your gauge is wrong and your motor is likely fine. Ringfree is good stuff if used correctly.

 

[BonairII]

Re: 1963 Starflite 75hp low compression Stuck Rings?

All 4 cylinders being that consistently...and low....is suspect in my opinion. Did you use a "screw-in type" compression gauge?

Find another gauge and see if they stay the same(which i doubt).

 

[heryrg2711]

Re: 1963 Starflite 75hp low compression Stuck Rings?

it does run, slow, no power at full throttle.
I don't think it's the gauge, tried the test twice with different gauges, both screw in types and both times the results were the same. The motor is old and probably sat for a while, leads me to think all rings are stuck, possible?

I put abit of oil in the cylinder and compression was higher, doesn't this mean rings are stuck? I will try this in all cylinders tomorrow.

 

[jbjennings]

Re: 1963 Starflite 75hp low compression Stuck Rings?

I had a 4.5hp mercury single cylinder that had 60psi and had totally stuck rings. It is possible that they're stuck, except for the fact that it runs. I don't think it would run at all with 55psi. I couldn't even get that single cylinder merc to hit a lick even with a high speed drill spinning the flywheel.
I really think you have 2 bad gauges.
If it idles at all, I'd almost bet that you do.
JMO,
JBJ

 

[heryrg2711]

Re: 1963 Starflite 75hp low compression Stuck Rings?

i think i'll buy a gauge today and see what happens. The motor does idle
Just to make sure, with 55psi should this motor run and idle??

 

[jbjennings]

Re: 1963 Starflite 75hp low compression Stuck Rings?

No, I don't believe it would do a thing.
JBJ

 

[JB]

Re: 1963 Starflite 75hp low compression Stuck Rings?

What jbj said. The probability that all four cylinders would go bad by the same amount and at the same time is very, very low

My guess is a bad test. Cold, dry, plugs in, weak battery, bad wiring to the starter, etc. If conditions and technique are not correct readings will always be (incorrectly) low.

Go to the Top Secret File ^^^ and do another test, exactly as described there.

Let us know.

 

[heryrg2711]

Re: 1963 Starflite 75hp low compression Stuck Rings?

Cold, dry, plugs in, weak battery, bad wiring to the starter, etc.

The motor ran idle for about 15 min prior to testing, don't think it was dry, plugs were all out, battery is not weak and turns the motor easily, wiring i think is good because the motor runs and was on the water couple days ago.

I disconnected the (+) on the ignition coil, took out all the plugs and then used key ignition to turn the motor over. Would it make a difference to start the engine by shorting the starter solenoid? I don't see how bypassing ignition could ruin the test.

Thanks again!

 

[heryrg2711]

Re: 1963 Starflite 75hp low compression Stuck Rings?

Ok, results are in. It was a bad gauge, but i'm still a bit low. Now i got about 70psi all the way around.

When i added a bit of oil and retested, i got around 88psi, so i think my original guess about stuck rings is corerct. Im gonna try to find a bottle of ringfree and see what it does.

Any opinions? Or suggestions??

 

[Daviet]

Re: 1963 Starflite 75hp low compression Stuck Rings?

You could do a decarb on the engine and see if the compression comes up.

 

[heryrg2711]

Re: 1963 Starflite 75hp low compression Stuck Rings?

Will do a decarb, should i get ringfree and do that? Or is decarbing basically the same thing?