Logo
FULL SITE MENU

1984 Merc 200hp v6 compression test

C

ChocolateBayouGator

New member
I did a compression test today and here are the findings;

2) 108. 1) 95
4) 104. 3) 95
6) 103. 5) 92

I know from factory compression should be close to 120, and it appears one bank of cylinders is lower over all than the others and there is 15 psi difference from highest to lowest. The motor runs, hard to start when cold, but idles well. Do I need to go ahead and rering the pistons if I am taking the power head apart anyways?
 
re ring is a option providing the motor was never over heated. personally if i had to do it id resize the piston and start from scratch . id also do both sides.
 
Alright, found out lower unit was suspect, so not tearing apart power head just yet. Is there something out there that can be added to fuel to help increase compression in the powerhead, or maybe changing out cylinder head gaskets?
 
Depending on how is has been run, there might be a heavy carbon build up. Try decarbing w/a very heavy dose of SeaFoam. When I had my Mercury 200 hp I would do 16oz can /1 gal gas and 2 stroke oil just to be safe and the run for 15 minutes, let it sit for an hour or so to soak and then repeat until I used all the fuel in the small can/tank. I had a 3 gal tank I used so was an easy mix. It will really smoke the 1st couple of times. Then recheck compression.
 
You just let it idle about 15 minutes while on a hose so the water pump has water. Let it and repeat until the gallon of gas is gone through the engine.
 
Back
Top