Technical help needed for 2 stroke outboard from the brains trust

[crash n bern]

My boat mechanic and I are stumped, so I thought I would ask on here because this forum has the greatest wealth of mechanical knowledge. I know it not bike related, but some of us fish aswell, I'm sure.

My boat capsized when my yard flooded during cyclone debbie. The motor was under water (fresh) for about 8 hours before I could retrieve it. The next day my mates and I  removed plugs cranked her over sprayed her with CRC, dewatered and got her running. No problems. I started her up a few times over the next month or so and would have her running sweet. Took her out on the water and under load she would cut out. So I gave her to a mechanic, because I'm still dewatering bikes.

The mechanic has swapped over coils, cdi unit, pick up sensors, gearbox,  fitted a pullstart to eliminate the starter circuit etc. Motor has good compression. It starts and will run on a hose for as long as you want. But in the water it will conk out after say 20 minutes. It will start straight away and run fine, then randomly conk out. Each time it starts straight away and runs fine. The cutting out happens at random intervals. The only thing he hasn't replaced is the wiring loom, that will be the next effort. Someone also suggested crank seals. And also selling the motor and buying a new one, but I can't pass on a lemon. If anyone can shed some light or point us to something obvious that has been overlooked that would be great.

Its a low hour Mercury 40HP lightning 3 cylinder.


Thanks in advance.

[80-85 husky]

what about the ign line from the control box or is it a handle steer job?. got to be electrical shorting under load? OB's usually fluff about if its fuel related. not a drop of water still in the carbs floating about?

[crossedup2]

Sound odd but have you checked the fuel tank vent?

Peter B

[crash n bern]

Husky, yes the mechanic fitted a pull start to disconnect the control box. But it does seem electrical. The motor runs smooth until it conks.

Peter B, the obvious, haven't checked, but you could be onto something

[pokey]

Multi cylinder. if it conks out clean and doesnt splutter its electrical issue.
 I read it does this only under load.

Have we isolated the over heat sensor? I note it lives directly next door to a component Mercury call the stopper.

http://www.boats.net/parts/search/Merc2/Mercury/40%20LIGHTNING%20XR%20%28International%29/0N000513%20THRU%200N056164/Electrical%20Components%28Electric%20Models%29/parts.html

[bazza]

Is that model 2 or 4 stroke? no shit got in to water spout (out) holes causing overheat and cut out?
Lucky my yamaha 60hp still going strong.

[crash n bern]

Thanks Pokey, just msg'd  your advice to the mechanic and he's onto it. I told him yesterday it will be a 10 cent part that we've overlooked.

Bazza, i'st a 2 stroke, plenty of water coming out of the spout. My guess has been as Pokey has said electrical. Water damage comes back to haunt you in the form of corrosion. I've been having to pull apart starter motors and clean rust off armateurs and free up brushes on everything that went under.

[80-85 husky]

MOBIL (My Old Brother In Law) sank the 225 evinrude in 10 metres of h2O. we managed to refloat it then unplugged the plugs, drained all trhe carbs, cranked her over for a bit, hooked up a tinny tank and replugged it and fired her up. instructions were "run it for an hour", still going strong today ...(the gbox poohed itself 3 years later...we forgot to drain that).