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

[fleetwin]

A relative on the west coast has a larger boat with a 120hp force along with this 25hp merc auxiliary engine.   Horrible combination, I know.  The 25hp is a remote electric model with its own controls/key switch up at the console, another horror story.   I’m guessing the Merc is a 90s model, it has a silver strip around the cowl, I can get its serial number if that will help.

In any event, he killed the started motor trying to get it to fire up, and insists it has no spark.  Insists that all safety switches are properly positioned.  Being an OMC guy, all I can do is troubleshoot this kind of ignition like it is an OMC.  So, the first thing I would do would be to eliminate the “stop circuit”.   Need, less to say, I know nothing about the Merc wiring or how to find the stop lead coming from the key switch back to the engine’s “switch box”.  I’m hoping this lead has a screw connection to the switch box so it can easily be removed to check for a faulty stop circuit.

So, am asking for guidance here, that I can hopefully relay back to my brother inlaw, so he doesn’t spend big bucks guessing, and replacing good parts.

Thanks

Don

[billw]

Sorry, Don…I just saw this now. I don’t visit this site too much anymore. 25s were not that common in my area, back when I was gainfully employed fixing two-stroke Mercs. A serial number would be good. I still have most manuals. Usually, two stroke Mercs will have the stop wire the same color as OMC…Black/yellow.

Long live American manufacturing!

[fleetwin]

Thanks Bill!  I did figure out that the stop wire has that same color code as OMC/ black with yellow tracer.  My brother inlaw disconnected the stop lead, got spark, then found that the stop lead had been melted/shorted to the block, so the engine is running again.  But, I am sure there will be more issues, he is a nice guy, but tends to wreck stuff fiddling around with it.

Now that I look at a picture he sent me, looks like it is a 9.9hp, not a 25hp.   Looks like the serial number is:  DL 266900.

I can email a picture of the engine if that will help, probably won’t post here due to size.

Thanks buddy, hope all is OK.

don

 

[seakaye12]

fleetwin wrote:

Thanks Bill!  I did figure out that the stop wire has that same color code as OMC/ black with yellow tracer.  My brother inlaw disconnected the stop lead, got spark, then found that the stop lead had been melted/shorted to the block, so the engine is running again.  But, I am sure there will be more issues, he is a nice guy, but tends to wreck stuff fiddling around with it.

Now that I look at a picture he sent me, looks like it is a 9.9hp, not a 25hp.   Looks like the serial number is:  DL 266900.

I can email a picture of the engine if that will help, probably won’t post here due to size.

Thanks buddy, hope all is OK.

don

 

Don if you want….always feel free to email me a picture that needs re-sizing to post here.  Just takes me a second and I’ll e-mail the smaller version back to you

[fleetwin]

Thanks!!  I just can’t seem to figure it out.   Don

[outbdnut2]

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

[fleetwin]

outbdnut2 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

[outbdnut2]

fleetwin wrote:

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.

I haven’t found a good serial number to year list for all Mercurys since the oldmercs . com website disappeared.  It seems that they changed some formats occasionally over the years and that doesn’t help.   Sometimes I can get close to the year by looking up parts I don’t need, like carb kits, in my 2004 Sierra paper catalog, where it will list year, or year range for some motors along with a serial number range column, but it’s not complete.  At least some of the online parts dealers like Marineengine have serial number input for some year ranges that gets you to a parts list, but to use it, it sometimes gets you to a HP list where you have to click on a few models of that HP to find your serial number – confusing!

Dave

[outbdnut2]

I found the site below that lists Mercury serial number ranges by HP and year from 1969 to 1996.   Click on the HP range in the left column and the chart for those HPs years and serial numbers will come up.

They leave off the “0” that’s in front of the letter at the beginning of the serial number.

Dave

https://maxrules.com/models/Merc_model_files/

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