need help with compression test...

nguyen80

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Joined
Aug 23, 2009
Messages
19
i have a etec 115 outboard....E115TSLECM 1998 , idle fine and cruising is fine but once i give some gas, engine cut off. i recently did a compression test and it shown.

cyl 1 85psi
cyl 2 100 psi
cyl 3 70 psi
cyl 4 95 psi

can you tell me what this meant? i also just bought a adjustable spark tester but i couldn't get any spark off the wire to the spark plug..
 

wilde1j

Vice Admiral
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Apr 15, 2002
Messages
5,964
Re: need help with compression test...

i have a etec 115 outboard....E115TSLECM 1998 , idle fine and cruising is fine but once i give some gas, engine cut off. i recently did a compression test and it shown.

cyl 1 85psi
cyl 2 100 psi
cyl 3 70 psi
cyl 4 95 psi

can you tell me what this meant? i also just bought a adjustable spark tester but i couldn't get any spark off the wire to the spark plug..

Well #1 & 3 are not too good. I would try decarbing several times in hopes of a stuck ring or two and retest. If still bad, time to pull the heads and exhaust covers for a closer inspection, as there may be cylinder damage or a head gasket issue.

Decarb: http://forums.iboats.com/showthread.php?p=2648076#post2648076
 

jtexas

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Oct 13, 2003
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8,646
Re: need help with compression test...

A good compression result is when the lowest cylinder is within 5 or 7% or so of the highest. If you recover that much compression from a decarb be sure to post the result here.

Did you repeat your test a couple times, just to make sure? Does your compression tester screw into the spark plug hole, or is it the other kind? It's important to use consistently the same procedure on each cylinder, including, starting with a known-good, fully charged battery (to be sure you get consistent cranking speed).

Your spark tester...don't attach it to the spark plug - clip it to the engine block.
The half-inch gap on the tester plus the spark plug is just too much resistance...... Also, if you'd just finished the compression test, you might have forgot to reattach the emergency lanyard.

Good luck, keep us posted.
 

nguyen80

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Joined
Aug 23, 2009
Messages
19
Re: need help with compression test...

thanx for the response....i forgot to mention that i did rebuild the carb, just pull the carbs out and took another look to find out that one of the core plug came off :eek:, also pull the plugs and to find out that one of the plug is gap is bend so much that it touch the gap. and while putting the carbs back, another problem came up. One of the fuel line was tore up and a little puddle of gas sitting on the bottom carb... great...after all problems fixed, went and get some deep creep seafoam and spray the engine and carbs. hopefully all problems are fix, waiting for a nice day to drop the boat and take a test run, and prob gonna test the compression again after a test run.. thank you for all ur help.
 

AlTn

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Mar 9, 2010
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2,813
Re: need help with compression test...

might be wise to determine why the sparkplug gap closed before you run the engine
 

jtexas

Fleet Admiral
Joined
Oct 13, 2003
Messages
8,646
Re: need help with compression test...

if your spark plug electrode was bent all the way down, it's a good chance it was hit by a piston.

if you pull the cylinder heads now, it might still be repairable.

if, on the other hand you run it enough for the decarb, then take it out for a test run, there's a good chance you'll tear it up beyond repair.

sorry, wish I had better news.....
 

nguyen80

Cadet
Joined
Aug 23, 2009
Messages
19
Re: need help with compression test...

not what i want to hear , i just remember that i put in the wrong side plug last yr and i think the piston tore up the electrode on one of the plug..i guess i am gonna pull the head and see what 's goin on in there. I will update if i find anything wrong in there. so what should i look for when i pull the head? thanx.
 
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