97 Yamaha SWII 150 low compression one cylinder

[mac83]

Yesterday, I was tuning up my motor to get it ready for new season. Before we started, we ran a quick compression test. All cylinders were 120 PSI except bottom port side read 110 PSI. I know that if it’s within 10%, it should ok. I’m looking for some wisdom from the thread on what you would do. I’d love to be able to get a couple more years on it but I have to have reliability and this motor has been nothing but!

Thanks I’m advance.

 

[seasick]

The two lower cylinders on the SX motor has lower compression by design. I would expect a little lower reading in a perfect world on 2 cylinders. That said, a reading of 120 psi for all but one cylinder and 110 for the other is excellent for a motor that is almost 24 years old. To be honest, there isn't much you can do at this point to extend it's life. t is already extended Just keep the maintenance up, use decent gas, continue to add a carbon cleaner like ring free if you have been. ( If a carbon cleaner has not been added in the past, doing it now may not help all that much but it won't hurt.

 

[mac83]

Thanks so much! I’ve run i
Ring free plus additive religiously since I’ve owned it. I’m not ready bite the bullet yet or a 4 stroke

 

[Topjimmy]

My 1994 SW 150 is around 115-120 all cylinders for the last 10 years and runs great and probably will for the next few years these motors are TOUGH! although gas guzziling Stinkers

 

[DennisG01]

Yup - you're good. I woudn't worry about it one bit. It's very common for all of the cylinders to NOT be the same - even brand new ones can be different - even 6 different readings.