Reply To: Need help with later model Merc 25HP two stroke ignition system

[Don]

David Stanton wrote:

I’m not much into Mercurys either, but fix a few for friends and neighbors, so maybe I can help some.   Double-check that serial number, as the Merc serial numbers with a letter in them that I’ve seen all start with a zero “0”, so maybe that D is a zero.  That would make it 0L266900, which, as a 9.9 2-stroke, puts it in the serial number range of the link below.  Note that Mercury’s first 9.9 HP was, I think, 1986, and was a totally different (and in my opinion much better) motor than the 9.8 it replaced.  I’ve only worked on one of these and that was a 1986.

Good Luck!

Dave

https://www.marineengine.com/parts/mercury-outboard-parts/99/0g760300-thru-0t979999-usa

Dave, you are right, the D must be a zero.   I never understood the “merc method” of identifying engines, seems complicated and confusing.  Am wondering how you determine what year the engine was produced by using serial number.  Oh well.   Fortunately, I was able to help the brother inlaw diagnose his issue over the phone and it was a simple one.   The stop lead from the boat harness was chafed/grounded to the block.   But, even the stop leads seem confusing on this thing, seems like there is an extra stop lead “pigtail” buried in there.  Don’t know why it is there, perhaps to make a simple connection if a tiller arm was added.  Nonetheless, you unplug one connection thinking you have separated the boat’s stop circuit from the switch box, but you really haven’t.

I anticipate more calls for help with this thing, so will attempt to find a proper service and parts manual for it, thanks for the help!  Don