Setting WOT Timing

[Roy W.]

I read references to setting WOT timing at .150 (the equivalent of 25 degrees) I'm assuming this is .150 BTDC on #1 measured with a dial indicator. I've set timing this way on breaker point ignitions, but how do you set timing this way on a Mercury breakerless system? I'm still doing it the old way with the boat tied down on the trailer and using a timing light while holding the advance lever wide open and blowing water all over the place.

[Bill Rogers]

Just spin it with the starter. I prefer to remove the plugs and terminate the plug wires on a spark tester. With #1 at 0.150" BTDC, adjust the timing pointer to exactly 25 degrees. Hold the throttle open far enough to fully advance the trigger, spin it with the starter and use the timing light to check. Spark advance/retard modules must be removed or this procedure might over-advance the timing at higher rpm

[bill mason]

what and where are the advance/retard spark modules??

[Bill Rogers]

Bill - I think the modules only came on fishing motors. I don't think any of your motors have one

Usually they're mounted on top of the block over toward the port side. On early models they were up front above the carbs.

[bill mason]

gotcha thx for reply

[Roy W.]

Why not just pull the kill switch ? Is there any reason why I can't make a new pointer for the 25 degree mark ? I don't think my factory pointer will move that far. My advance/ retard and detonation modules (200 EFI) have already been deep sixed.

[Bill Rogers]

Roy - when you set #1 to 0.150" BTDC, it'll be very close to 25 degrees - shouldn't have to move the pointer very far. We are talking about a V6 Merc, right? Don't pull the kill switch - the ignition has to be hot to trigger the timing light

[Roy W.]

Bill, Thanks for the input, yes it's a '98 200 EFI Merc. Duh.......on the need to trigger the timing light (senior moment).