Will Replacing Rings Increase Compression >105PSI?

[Shinyboat]

My 91 Johnson 50 two cylinder is running 105PSI in both cylinders. It looks like other Johnson 2 stroke 50s from the 1980s to 2000s on this forum are running as high as 140-150psi.

In the past I’ve increased compression of 2 stroke small engines by replacing rings only, but I’ve never worked on a larger engine. Do I have reasonable chances of increasing compression if I do rings only and don’t hone the head or replace pistons?

 

[Crosbyman]

are you having problems with th eengine ? is the gauge OK and accurate ??

 

[Scott Danforth]

Just replacing rings won't help.

First start with running ring free.

If that doesn't help, it's rebuild time

 

[Shinyboat]

are you having problems with th eengine ? is the gauge OK and accurate ??

Engine runs really well but is slightly underpowered.

Gage is definitely accurate!

 

[Shinyboat]

Just replacing rings won't help.

First start with running ring free.

If that doesn't help, it's rebuild time

I’ve never heard of this. Wouldn’t this significantly reduce compression? What should be expected?

 

[Crosbyman]

Engine runs really well but is slightly underpowered.

hum... will a ring job provide a cost effective solution on a "really well running" 32 year old engine.

 

[flyingscott]

I doubt that would be a good running motor with only 105 psi. How fast is the starter spinning? Both plugs out?

 

[racerone]

Head gasket is cheap.----Remove cylinder head to inspect cylinders.

 

[tphoyt]

I’ve never heard of this. Wouldn’t this significantly reduce compression? What should be expected?

Ring free is an additive that may or may not loosen up stuck rings and restore some compression.

 

[ONERCBOATER!]

I'm guessing ring free is like doing the seafoam treatment on a fully warmed up 2 smoker....as a decarb treatment.

If so this would be a good idea as I have had it make a world of difference on engines that had Carboned up rings and low or uneven compression.

Remember try everyone else's advice before mine... as I usually asking questions too.

Sean

 

[racerone]

Putting new rings on old pistons / worn ring grooves is a mistake !----Pull cylinder head now.-----Head gasket is cheap in the big picture of owning a boat !

 

[tphoyt]

I’m with Racer on this one.
If it’s a high hour motor it really needs to be inspected before anything is done.
The ring free can work in some cases but in my eyes you have a 50/50 chance of it helping a bit or helping to much. I have seen these snake oils free up so much carbon that things start coming apart and causing a lot of damage. As in rings breaking and scoring cylinders.
An inspection is worth it’s weight in gold.
Best

 

[Faztbullet]

It needs inspected ..as in cylinders miked, most likely bored to .020 and a set of 60HP carbs installed...Vola!! more compression and 10Hp