2007 Mercury 50hp Compression numbers

[Sealuvrrr]

Hi,

I will be looking at a 2007 boat/motor combo this weekend to purchase. The motor is a 3 cyl 50hp 2007 Merc. The motor was serviced and pistons decarboned etc. in 2011. On the bill, the tech listed the compression numbers: #1 115, #2 125, #3 130. I am concerned with the spread between #1 and #3. Should I be? If it demos ok are we good? Seller states that boat is used often and there are no problems.

Michael

 

[Dave1027]

Re: 2007 Mercury 50hp Compression numbers

Going by the 15% rule, the highest cyl at 130 x .85= 110.5. You are OK since the lowest cyl is 115. Certainly not ideal but OK.

 

[JB]

Re: 2007 Mercury 50hp Compression numbers

She is just barely acceptable, sealuvrrr. Some say +/- 15%, others say +/- 10%. I am of the 10% persuasion.

I would first want to know all of the conditions under which the test was taken and exactly the procedure used. Seller is going to paint the rosiest picture he thinks he can get away with, and "no problems" means none that he wants to do anything about.

I would ask the seller to do a decarb procedure and retest exactly as described in the Engine FAQs Forum. Otherwise I would pass.