Help to Diagnose 90hp Mariner Suddenly Won't Start

Hope someone can help diagnose this late season engine problem. Don't know what might be important, so I'll just put in all the facts.
This is a 90hp Mariner outboard.
At the start of the season I noticed fuel mixture was being sprayed on the inside of the engine cowling (hood). I traced the problem to a fuel line low on the right side of the motor (as you face it from the stern). The rubber hose was cracked/ worn, and the fuel mixture was spraying out. I replaced the rubber tubing, and ever since then, the engine worked great all summer....until last night.
Just after sunset on the way in, we stopped to help a boat in distress. They had a dead battery and jumper cables. I undid the cables from my battery, and they started their boat with my battery (it took only 1 turn of the key for them to start). I then, put my cables back on my battery and went to continue in, but the engine would not start.
At first it would only crank, but soon (and now) cranks and 'does start', but only for 1 second or 2, and then kicks off. I mean, the engine cranks, catches, the oil beep, and water exhaust come on, then it quits, it never really gets going.
I tried reapplying the battery cables. Made sure there's gas going from the external tank to the engine, checked the 1 fuel line I replaced months ago...all are ok.
The primer bulb gets firm as usual. All the lights, stereo etc. work, and the engine does crank normally, and catch, but only for a second.
Any ideas on what it could be?
On what I should check next?
Was the whole incident with undoing the battery cables, and jumping the other boat, just coinidental, as seems likely?
Anyway, I spent one cold night stranded on the lake and just got back today.
All ideas welcome...........................

Re: Help to Diagnose 90hp Mariner Suddenly Won't Start

Maybe you bunped the kill switch on the control set when you were wrestling with the battery.

(wouldn't be the first, or the last one to do it.)

Along that vein, other wires accidentally loosened up.

It could be coincintental. If you only replaced the one hose, another may have blown out internally and plugged up the fuel circuits in the carbs. When they look bad on the outside, they've been bad on the inside for a long time.

hope it helps
John

Re: Help to Diagnose 90hp Mariner Suddenly Won't Start

Thanks for the suggestion, j_ Martin,
Didn't have a chance to work on the boat till today 9-8, as you'll recall it concked out Labor Day night, I didn't get back till the next day, then had to arrange a tow, then several days rain.
Anyway, it's working again!
I fixed it, lol....that's what I've told people around the marina today.
Actually it concerns me, because I don't understand it, and that means it could happen again. I have no more idea 'why' it's starting then I did 'why' it wasn't. Any ideas welcome.....
Checked kill switch, no kill switch, this boat.
What also I did today is go back to the battery cables/ wires. The whole problem started Labor Day when we stopped to help a smaller craft, 'I thought' I removed all the cables/ wires my battery and started their boat from my battery ( some mentioned possible difference in voltage?).
Today I noted on the positive (red) terminal a smaller red wire beside the main red cable. As far as I know this smaller positive lead powers only the boat stereo. Unlike the main positive cable, the main negative (black) cable, the negative ground, this smaller positive wire is pretty 'narrly' having lost it's connector and being just bare copper on the end (clean and free of corrosion though).
I tried cranking the motor without this wire being attached...got loud backfire.
Then reattached it, made sure all else attached and clean to battery terminals, and...started right up and ran fine......Great!...but..why?
I guess I better trace 'where' the small red wire goes...oil alarm, ignition, a kill switch no longer active?
Just wanted to keep all informed, and thanks for the help.

Re: Help to Diagnose 90hp Mariner Suddenly Won't Start

First thing is pull your spark plugs and see how blackened, sooted they are.

How much trim angle did you have on the engine?

Is it possible that you 'flooded' the motor and since it has had time to dry out that all seems normal again?

If the plugs look poor, try a new set, and/OR carry a new set along for when this happens again.

Re: Help to Diagnose 90hp Mariner Suddenly Won't Start

On my 115 Mariner the small red wire supplies +12V to the ignition, gauges, etc. The large red just goes to the starter and tilt/trim.