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Help with timing Merc 20hp 200

scubadoo2

scubadoo2

New member
Hi, and help anyone please!! My Mercury 20hp model 200 can't be timed to 33 degrees BTDC, i can only get about 24 degrees with the trigger as far advanced as it can be. It's a new trigger, new switchbox, new spark coils, and spark plugs. Anyone know what could be the cause of this?
Any help appreciated.
 
No the key is in place. I was trying to time this with a timing light turning it over without running it. The engine was in forward at full throttle setting. Will this make a difference? I will be mounting it to my boat and checking it running at too.
 
33 degrees is max spark advance, primary pickup is 3-7 degrees BTDC. The carb should just begin to open at 3-7 degrees BTDC you need to check max advance on the water in forward gear at WOT. Pick a nice day where the water is smooth. Be sure and turn the motor off to make the adjustment the flywheel will never say ouch.
 
kimcrwbr1 said:
33 degrees is max spark advance, primary pickup is 3-7 degrees BTDC. The carb should just begin to open at 3-7 degrees BTDC you need to check max advance on the water in forward gear at WOT. Pick a nice day where the water is smooth. Be sure and turn the motor off to make the adjustment the flywheel will never say ouch.
Click to expand...

What does "primary pickup is 3-7 degrees BTDC" mean. I tested the engine on my stand running and at very low idle, the timing -2 degrees, running with the grip twisted to start, butterfly opens a very tiny bit (not sure what rpm it is at) the timing is +6 degrees advanced. Trigger rod has no more room for adjustment. The rod is no where near the position is was at previously before the old switch box and one of the coils packed it in.
 
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Primary pickup is engine sync between ignition timing and throttle opening it sounds like it is within spec. Max spark advance should happen around 3500-4000 rpm enigine speed is not important as long as the spark advance never goes over 33 degrees BTDC at wide open throttle. What is the serial number of your motor?
 
It is a Canadian serial number, 7068346. Thanks for the input, it seems to run very close how it did before , just seems to not push the boat as fast.
Only 28 kilometers per hour pushing a 12.5' inflatable with two people. My new 2016 20 hp Mercury 4c will push my 14' Mercury Hypalon HD with two people at 38 kph.
 
You can time that motor in a barrel, and safely, by removing the cam atop the carb. That allows you to hold her wide open safely--about 3,000 rpm.

Jeff
 
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