How do I do a compression test?

[DKennimer]

Hello all,

I just bought a compression gauge and want to do a compression test on my 1981 Evinrude 150V6. I just want to make sure I do it right. I have heard that I can damage the ignition system if I do it the wrong way. Should I disconnect the kill switch before taking the spark plugs out and doing the test? Also, what is it when people talk about grounding the wires to the block while performing the test, is this necessary???

Thank you!!! I don't want to screw anything up!!!

 

[fattypackard]

Re: How do I do a compression test?

disconnect the fuel line, pull all the plugs, turn over the motor by crossing the starter connections. checked each cylinder. they should all read around 110 - 120 and all be within 10 psi of each other.

thats how i do it atleast....somebody else chime in if thats wrong...

 

[mark1961]

Re: How do I do a compression test?

Motor should also be run first to warm up so that its near normal operating temp when the compression is checked.

 

[F_R]

Re: How do I do a compression test?

You will get a dozen how-to replies on that question. That is why I quit answering. Not worth the arguements that are sure to come.

 

[tashasdaddy]

Re: How do I do a compression test?

this is the official answer from iboats forums. http://forums.iboats.com/showthread.php?t=313963&highlight=compression

 

[DKennimer]

Re: How do I do a compression test?

You will get a dozen how-to replies on that question. That is why I quit answering. Not worth the arguements that are sure to come.

I hear ya, I just want to make sure I don't screw something up! But, I understand what you are saying---lots of opinions out there... But, I do need the information, and will consider all, this is the best forum!

Thanks again!

 

[tashasdaddy]

Re: How do I do a compression test?

did you read the link i gave you????

 

[DKennimer]

Re: How do I do a compression test?

Hi tashasdaddy,

Yes I did and thank you for the information! Since I don't have a set of muffs (yet) I just started the engine for 10 seconds to lubricate the block, and this is what I came up with:

Cyl:
#1 106
#2 100
#3 105
#4 104
#5 104
#6 104

I was pretty happy with these numbers considering it is a 1981 model, what would be the difference if I did warm the engine up first??

Thank you for your help, I really appreciate it!!!!!!!

Derrick