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Question

hi working on a 2005 carb. 200hp mercury engine idle fine, but while cranking with a new battery and the spark plugs out of the block i cannot get the timing allignment pointer to line up it is jumping all over the place.I manually advance the timer base and cannot get the marks to line up. Timing light is on the wire correctly i should be at 25 degrees BTDC or atdc whatever the flywheel key and magnets are good triggers voltage and resistance are in speck what else is there?

Answer 1

Brad J hit it on the head follow the man's advice!

Answer 2

OK.

There is nothing wrong with using timing light on this engine while it is cranking. That is actually the correct procedure for setting a basic timing.

For starters lets talk about your timing light. Make sure you are not using a light with a variable timing feature. These can read wrong on outboards. Also bear in mind that some timing lights are more shielded to RFI (radio frequency interference) than others; this can be a big issue on RFI rich engines like outboards. A RFI sensitive light may “misfire” when it picks up fields produced by the other cylinders when firing. You can sometimes negate or lessen this by insuring the cord for your inductive pick-up is routed away from the other plug wires.

Second, I see that you have the plugs out of the block. There is nothing wrong with that; just make sure the plug wires are somehow grounded to the engine block (in the shop we use a spark checker). If you need to you can put a bolt in the plug end of the wires and ground that to the block. Make sure all the plug wires are grounded or you could damage the ignition system. Also keep yourself clear of the plug wires when cranking the engine.… You could damage you!

The last thing you need to do is take the throttle advance cable (there are two cables that go into the cowling of the engine. The top one is the throttle and hooks to a large lever on the port [left] side of the block) Now when you have this lever cable loose you can hold the top of the timing lever all the way towards the stern of the engine. With the arm in this position have someone crank the engine and check your timing. If you still don’t see the marks near the timing pointer then you need to stop! If your marks are way off you need to take the engine to an authorized repair shop… You may have a problem with the bias circuit in the ignition + that’s something you need a knowledgeable tech to troubleshoot for you.

Good luck and I hope this helps!

Answer 3

To use a timing light the engine must be running.  When you use the starter motor the engine does spin consistently and the actual point at which the ignition sparks may vary.  If the engine is idling at say 700 RPM the spark point will be much more stable and the timing mark for low speed timing mark should be quite clear.  When you increase engine speed to say 2500 RPM the ignition will be fully advanced and the high speed timing marks will look like they're standing still.

Timing is usually BTDC to take advantage of compression to insure there is complete flame spread across the cylinder.