Setting maximum spark advance question.

[jhodge]

86 merc 3 cyl 60 hp
The manual says to put engine in a test tank or if mounted on the boat to put in the water for setting the max spark advance. Is a test tank something more than a 30 gal garbage can? That's all I've got for now. The engine is mounted on the boat so figured I would put it in the water. During this test the engine is run at 5300 to 5800 rpm in forward gear, while the spark advance is tested with a timing light and adjusted to 23 degrees max. Can this safely be done while still tied to the boat trailer, or should we be running thru the river? Seems kinda dangerous tied to the trailer but thought I would ask because it might simplify making the adjustment if not bouncing around on the water? Either way it will take two people to do the test, unless someone has a better way. Thanks JH

 

[CharlieB]

Re: Setting maximum spark advance question.

A barrel is too small, even a 10 HP will throw much of the water out before you get a chance to turn on your timing light.

Ideally timing should be verified WOT while running, either in a test tank or on the water. In the real world many use the cranking method spelled out in some OEM Service Manuals.

Remove the spark plugs and ground all the plug wires.

Remove the prop.

Connect the timing light.

Connect a remote starter button.

Turn the ignition ON

Shift into Forward gear and WOT

Press remote starter button and verify timing with your light, adjust if required.

Some Service Manuals specify setting timing 2 degrees less than specification to allow for timing advance once running. I haven't yet experience this problem.

 

[jhodge]

Re: Setting maximum spark advance question.

Charlie B. Thanks for the heads up on setting the max spark. I haven't seen this procedure in the Merc manual but it sounds like something one person could do safely. I will try it and then do a test run to see how it is under real operating conditions. Much appreciated. JH

 

[jhodge]

Re: Setting maximum spark advance question.

I made one small change to the method that Charlie B gave for checking max spark advance. Rather than remove the prop I put the bottom end in a plastic tub to keep my size 11's away from it. Seemed like a quicker method than removing the prop. It doesn't spin too fast at cranking speed anyway. So, it would be slow damage to the lower extemities. JH