Completed the compression test on my '85 merc 260
 

1- 132
3- 135
5- 130
7- 133
2- 155 noticed fuel in cyllinder
4- 150 also noticed fuel in this cylinder
6- 140
8- 145

How does it stack up? what does it mean when there is a noticeable amount of fuel in the 2 cylinders? Thanks guys. at least now I assume I have arrived at decision time. Thanks for any advice.

Jim

Re: Completed the compression test on my '85 merc 260
 

Compression test should be run on a motor that is "warm" not cold.
Disable the kill switch (or if it does not have one, remove the coil wire from the distributor cap and ground it). Open the throttle plates.

Then check each cylinder.


When you say you saw fuel in the cylinders, please elaborate.

Re: Completed the compression test on my '85 merc 260
 

yeah it was done cold. When I removed the #2 and 4 spark plugs I noticed fuel on them.

Re: Completed the compression test on my '85 merc 260
 

fuel ..or water ?

Re: Completed the compression test on my '85 merc 260
 

definitly fuel

Re: Completed the compression test on my '85 merc 260
 

JGB you having probs or just got some extra cash ???

Re: Completed the compression test on my '85 merc 260
 

It's certainly not an xtra cash issue. The Problem is max rpm only 4500, This motor has a little hotter aftermarket cam. engine iis running rough, carb has been rebuilt twice in two days. I'm at my wits end.

jim

Re: Completed the compression test on my '85 merc 260
 

Formulaz thanks, throttle was WOT during test. Carb as I mentioned in previous post has been rebuilt twice in two days ccause that's what I thought was causing the motor to run rough.

Re: Completed the compression test on my '85 merc 260
 

And I am getting blow by from the Valve cover breathers and not just a little.

Re: Completed the compression test on my '85 merc 260
 

was told engine had 40 hours on a rebuild. certainly can't belive that.

Jim

Re: Completed the compression test on my '85 merc 260
 

So would that mean I am looking at a rebuild if that's what the leak down test showed? thx


Jim

Re: Completed the compression test on my '85 merc 260
 

Proof is in the leakdown test,i did my motor a few wks ago and my weakest cyl had 120 psi crank compression (after 10 cycles),80% leakdown!!!,best cyl had 10 % leakdown and was bumping 160 psi after 4 cycles of motor. Funny thing was boat ran ok,was 1/2 mph off normal speed and didn't have much blowby. When you did your compressioin test did the lower press cylinders take more turns/cycles of the motor to get to there max? If they did it is definately weak,leakdown test,post your results,Smitty

Re: Completed the compression test on my '85 merc 260
 

Or they rebuilt it, and got the ring gaps too wide. This pearl of wisdom comes from the blowby encountered after a friend rebuilt his engine back in high school. That car was liking driving around a oil geyser!

Michael

Re: Completed the compression test on my '85 merc 260
 

the blow by seen is a alot. there are 2 mr gasket breathers on the valve covers(one on each side. When I slow down to idle after a run and open the engine hatch it looks like a smokehouse.

Carb was rebuilt twice because after the first rebuilt it started flooding the engine after 10 min of run time.


The motor has a mild aftermarket cam which I thought it should be running higher than 4500 rpm.