Proper compression testing on outboard?

[JoeMan]

Need to know the 'proper' way to compression check an outboard. I've found a few threads here on the subject, but the information is different, so let me just get clarification for what I don't know.

I know that I need to warm up the engine, remove all 3 plugs, attach the gauge and crank for several seconds to get a good reading. Some threads I've read here tell different ways to disable the electronics prior to testing, and other advice mentions nothing about that. If I need to disconnect a wire to protect electronics first, tell me which one to unhook, and where it is. I'm still learning some of the outboard language. Thanks mates.

 

[jaymasta]

Re: Proper compression testing on outboard?

Need to know the 'proper' way to compression check an outboard. I've found a few threads here on the subject, but the information is different, so let me just get clarification for what I don't know.

I know that I need to warm up the engine, remove all 3 plugs, attach the gauge and crank for several seconds to get a good reading. Some threads I've read here tell different ways to disable the electronics prior to testing, and other advice mentions nothing about that. If I need to disconnect a wire to protect electronics first, tell me which one to unhook, and where it is. I'm still learning some of the outboard language. Thanks mates.

Warm up the motor so it is at operating temperature, and then remove all the spark plug wires but leave all the spark plugs in, ground out all the spark plug wires to the block so that they still spark into the block, and then remove spark plug #1, and do test, put spark plug #1 back in, and remove spark plug #2, do test, put spark plug #2 back in and remove spark plug #3 do test and put back in etc...never do a compression test with any plugs removed except the one that you are testing and adding the compession tester anyways so its like there is still spark plugs in all of them, and you remove all the wires so that the engine won't fire up on you and cause a disaster, just remember to ground all the wires to the block firmly so they don't fly off when turning over yet still fire...anyways hope you can understand this maybe someone will chime in with an better written way

 

[AMD Rules]

Re: Proper compression testing on outboard?

Check this short video out. It shows some techniques for spark & compression test.

Topic: TMD Video Chronicle Comp and Spark check

 

[dhauser]

Re: Proper compression testing on outboard?

Hi

I checked out that video - and wondering, what is the plate he has attached when doing the compression test? Is that what he's using to ground the wires to the block? Hard to tell on my little laptop screen...

Also, who is this guy, and does he have other videos online somewhere?? ;-)

Thanks

 

[LubeDude]

Re: Proper compression testing on outboard?

Never do a compression test with any plugs removed except the one that you are testing

I don`t see where this is an issue, aspecialy if you can just pull a kill switch. One cylinder has nothing to do with the others and the engine spins much easier. I always do it this way, cars, trucks, boats etc. Also. it`s best if you can open the throttle some.

 

[j_martin]

Re: Proper compression testing on outboard?

I pull all the plugs, pull the kill switch. Leave the key switch off. Hook up a mash-button switch (or just a jumper wire) to the starter solenoid. Jam the throttle valves open with a wood block. Check all six in a couple of minutes. No sparks, and just me-no helper.

John