Compression ok??

[wishihad]

Just did a comp check on my 88 70hp 3cyl merc. Top 2 were 105lb bottom was 90lb. Should I be concerned?
tnks

 

[05GlastronSX]

Re: Compression ok??

my general rule of thumb is that they should all be within 10-15% of eachother and yours is just at that 15%. try preforming a decarb and see if that brings up compression any. if not, you should investigate further.

 

[wishihad]

Re: Compression ok??

my general rule of thumb is that they should all be within 10-15% of eachother and yours is just at that 15%. try preforming a decarb and see if that brings up compression any. if not, you should investigate further.

Tnks
Will try this weekend and report back.

 

[studlymandingo]

Re: Compression ok??

The numbers seem just a bit low as well. Do a thorough decarb as suggested, and also spray each cylinder down through the spark plug hole with Deep Creep. Let it sit overnight like this. Run it the next day until the smoke clears up, bring it up to operating temperature before checking the compression. You will probably get some higher numbers.

 

[timmathis]

Re: Compression ok??

Like said above. Give it a good decarb. And retest the compression. You may be O.K..
Tim

 

[wishihad]

Re: Compression ok??

Like said above. Give it a good decarb. And retest the compression. You may be O.K..
Tim

Tried to find some decarb @ west marine today but they had none...? Will have to order.

 

[timmathis]

Re: Compression ok??

Advance auto has seafoam and deep creep on the shelf In most of their stores if you have one in your area. Also you can try NAPA. I'm not sure but AutoZone may carry it .
Good Luck, Tim

 

[timmathis]

Re: Compression ok??

If you can't find Deep Creep / seafoam. You can try Ring Free or Mercury power tune.
Tim