another compression question

[Dawgs]

will there be different reading with the same motor if i do a compression test with the motor in the back of my pick-up....then do the same test with motor on the boat all hooked up and ready to go?

 

[wilde1j]

Re: another compression question

Not if you remove all the spark plugs for either test.

 

[Dawgs]

Re: another compression question

the reason i ask is...im just figuring if its all hooked up it will have a secure ground...better crank...etc.....no?

 

[wilde1j]

Re: another compression question

I have no idea what motor you have and no idea why you would not just check it on the boat.

 

[Dawgs]

Re: another compression question

i have a 1990 johnson 150...the reason im not checking it on the boat is because its in my pick up. i tested it in my pick up and got 70 psi on all 6 cylinders but it seemed low

 

[JB]

Re: another compression question

Dawgs, 60psi is not unusual for a big OMC V6 and does not indicate a problem. 70psi is even better.

So many factors affect compression readings that you might get slightly different numbers on the transom, but that would not indicate a problem either.

 

[tashasdaddy]

Re: another compression question

agree with JB.

 

[jonesg]

Re: another compression question

Seafoam it, betcha get more psi.

 

[Dawgs]

Re: another compression question

i cant seafoam it unless its running...correct? i need to mount it then hook it all up first

 

[wilde1j]

Re: another compression question

That's exactly right.

 

[Dawgs]

Re: another compression question

call me stupid....but what does "OMC" mean?

 

[wilde1j]

Re: another compression question

Outboard Marine Corp., the parent of Johnson and Evinrude divisions. OMC bellied up in 1999-2000 and BRP acquired the assets of the bankrupt firm.