4 stroke compression test

[Dave S]

I have a couple questions regarding compression testing a 4 stroke outboard:

Do I open up the throttle while cranking over engine?

Should I take all plugs out or just one at a time?


THANKS!

 

[IMRINC]

All the plugs out and the throttle wide open. 5 revolutions of the motor is standard.

 

[Seafever]

That's got me curious.........why do you need the throttle wide open?

It's only going to turn over as fast as your starter will allow...

With the plugs out throttle makes no difference to compression from what I can figure.......

ok you've got the compression tester in one of the holes.....but still.........

 

[trendsetter]

That's got me curious.........why do you need the throttle wide open?

It's only going to turn over as fast as your starter will allow...

With the plugs out throttle makes no difference to compression from what I can figure.......

ok you've got the compression tester in one of the holes.....but still.........

The open throttle allows for more air and fuel to flow into the cylinders during the test. It provides a more accurate result of compression.

Another thing you should do is pull off the safety lanyard from the control box to ground the ignition system. Otherwise you may get sparks shorting out between the loose plug wires and the block.

And make sure you have a fully charged battery before the test.

 

[finaddict]

The open throttle allows for more air and fuel to flow into the cylinders during the test. It provides a more accurate result of compression.

Another thing you should do is pull off the safety lanyard from the control box to ground the ignition system. Otherwise you may get sparks shorting out between the loose plug wires and the block.

And make sure you have a fully charged battery before the test.

Wise and solid advice.