Compression

[bobwalter]

I have a new to me 1984 Merc, 200 hp engine. I ran a cold compression test today. All cylinders were at 120 except the middle one on the left. It was 140#. The motor has 449 hours on it. It has not been run in 10 years. Pre-purchase, a mechanic rebuilt all three carbs and ran engine on a portable fuel tank. Said it runs well. My plan is to go through and replace water pump, thermostat and lower unit lube. Drain and clean fuel tank also. My main concern is whether this difference in compression means anything. Is it significant? Do I need to worry? I need some advice.
I have ordered OEM parts and service manuals and as soon as they arrive, I will get started. I have a lot of experience with all types of engines except outboards.

Thanks in advance for any and all input.

Bob

 

[Scaaty]

Re: Compression

Did ya check it dry? Crank it verticle, put some oil in the cylinders, crank it a touch, and do it again. I think your OK anyway..don't worry about it. On the rest, your right on the money. Run 25-1 oil for the first few tanks of gas, then back to 50-1

 

[ddennis]

Re: Compression

Run some seafoam through it too. Good stuff. Cleans all the carbon out of the cyl's and helps clean (and keep)the goo out of the carbs...