Mercury 2.5 Timing

[rs2.2]

After a bit of advise regarding setting max timing on a 225 promax. When checking max advance with just no1 plug and the rest grounded to the block I can only get to 21/21 dev max advance then the trigger wiring hits the bearing carrier preventing any further advance. However if I remove the plug and crank the motor I get 25 degrees on the light? Is it normal to have a discrepancy with the plug in and out, if so which is the more accurate method for setting the max advanced please?

[25two.stroke]

Run it WOT at the ramp on the trailer and check the timing. Put a low pitch prop on, spin it up to 4500 rpms and you should get like 22 btdc

[OnPad]

All plugs out.
Is your idle stabilizer/advance module removed, or unhooked?
I've never had a problem getting 25°, maybe your trigger is jacked up.

[XstreamVking]

Sure the pointer is adjusted accurately? You using the one on the flywheel cover? I just use the dial indicator to prove TDC and for the desired number of advance

[rs2.2]

Thanks for all the replies. There’s no idle stabiliser on the motor, I’ve double checked the TDC pointer using a dial indicator and the 25deg mark at .150” and each time they come back spot on. The standard flywheel cover is fitted with the original adjustable pointer. I’ve always checked with all plugs out before it’s only that one of my early service manuals says about leaving no1 plug in so thought I’d try it!

[patchesII]

Thanks for all the replies. There’s no idle stabiliser on the motor, I’ve double checked the TDC pointer using a dial indicator and the 25deg mark at .150” and each time they come back spot on. The standard flywheel cover is fitted with the original adjustable pointer. I’ve always checked with all plugs out before it’s only that one of my early service manuals says about leaving no1 plug in so thought I’d try it!

Check all cylinders. If you still need more I’d look at the metal elbow where in goes into the plastic trigger body. That’s usually where you run into the first interference