Compression Test 500EFI
 

I'm looking at used 500EFI, what should the compression be?It has 400 hours on it. Change valve springs? Anything else? I figure I would run it for a year or so then freshen it. Any idea what its worth? Thanks, Doug

Re: Compression Test 500EFI
 

compression should be ideally over 150 with all cylinders within 10% of each other cylinder will fire with approx 100 psi realistically comp with 400hrs will prob be closer to 125.

really you should do a leak down test it will more accurately give you a better idea of the cond of the motor

Re: Compression Test 500EFI
 

From the Merc 500EFI Service Manual

Re: Compression Test 500EFI
 

......still stand by what I said....how many 400 hr motors do you know with 175 psi fresh broken in mtr yes........

Re: Compression Test 500EFI
 

Hey GOODT ..... maybe we should get your old Buddy Mr Cozzi in on this thread ??? :D

Re: Compression Test 500EFI
 

:evilb: actually we spoke hes really a great guy........

Re: Compression Test 500EFI
 

Joe,
I too was surprised that they called for a minimum of 175PSI. Seems high. It's also strange that it differs so much from the 525EFI Service Manual (below).

Dave

Re: Compression Test 500EFI
 

and both have the same copression ratio.........

with compression test I still go by the gen rules that I was brought up with ie...over 100 cyl is firing but bearly...all cyl within 10 % but the best way to tell the cond of a mtr is to do a leak down test....

Re: Compression Test 500EFI
 

yea ... he seems ok .... alot of friends here ..... I feel his pain though ...(52) .... not easy when the years pile up and you realize there is a stronger smarter YOUNGER generation ...........

Re: Compression Test 500EFI
 

42 here not much younger and I can feel the years piling up also...... :cool:

Re: Compression Test 500EFI
 

I had my 572,s tested average 225 pounds comp. I thought that was high,but thats what tested.

Re: Compression Test 500EFI
 

Hi Guys!
Joe is right on the money. A 400 hr. engine will only see 175 lbs. if the combustion chambers are loaded with carbon deposits! The numbers being consistent and in the 140s would satisfy me.
Ed

Re: Compression Test 500EFI
 

Thanks, Joe...right back at you!