1988 15hp mercury no fire when cold...

[dizzy_craig]

Absolutely no fire unless engine is warmed, either by sunlight with cover off, or as my uncle discovered, if you take a blow dryer to it... lol. This is really what he does to get it going everytime he takes it out. But don't think that was his first choice. He first replaced the coils, plugs and plug wires. When that didn't work, he figured out that when he had the top off for a while in the hot sun... it would start up and run great for the rest of the day, even though he had accomplished nothing with his tinkering. He then took it to a local boat shop, who called and informed him that there was nothing wrong with it. It had been in there lot in the sun all day. He told them to bring it inside early the next morning before it had time to warm up. They called the next day and said there was still nothing wrong with it. But sure enough, the next time he took it out.... same old problem. I'm thinkin it could be the switch box. He's been blow drying the area around the left coil, which sets right behind the "black box", which sets right behind what I believe is the rectifier??? I've tried disconnecting the black\yellow wires, which accomplished nothing... Any help with this puzzler would be greatly appreciated... Thanks much! Hopefully?

 

[achris]

Re: 1988 15hp mercury no fire when cold...

You'll probably be able to fix this one with a multimeter. While it's cold, check the resistance of the trigger coil and the stator. If you get an open on either one, that's the fault. If not, then it's probably the switchbox. I'd be checking that one with a DVA...

Chris.......

 

[dizzy_craig]

Re: 1988 15hp mercury no fire when cold...

Thanks Chris... I'm not extremely boat savy, I have to admit. Is there any way you might know where the stator, and trigger are located on this thing?? And if that is indeed the rectifier in front of the switch box...?

 

[achris]

Re: 1988 15hp mercury no fire when cold...

ok... Ignition systems 101..

The ignition system consists of 4 major parts:
1. Stator (is a set of wire coils and lives under the flywheel), which produces an AC voltage around 250-400 volts as magnets in the flywheel go past it.
2. Trigger (also under the flywheel) is a single coil that produces a pulse as a single magnet goes past it.
3. Switchbox, which stores the voltage from the stator in a capacitor, and discharges the capacitor across one of the ignition coils on the signal of the trigger. If the trigger pulse is positive, then #1 coil is fired, if it's negative, then #2 gets fired.
4. Coils and spark plugs.

There is also a 'kill' circuit (black/yellow wires). When you press the stop button you effectively ground the capacitor in the switchbox so it can't produce sparks, thus the engine stops.

Chris...........

 

[dizzy_craig]

Re: 1988 15hp mercury no fire when cold...

Thanks... think it is the switchbox. Having trouble finding out which ones are compatable. Does anyone know if 339-7452 a10 is compatable with 339-7452 a15, or a19? The box looks the same, and it shows to cover my serial number, but says it replaces a-15, and a19. Mine is the a-10.