72 115hp merc stops like a kill switch

[Alphabiatch]

Just got a 72 Cheetah w/ 115hp Mercury (also 1972). The idle, throttle and spark advance were all in need of adjustment. Got those pretty much dialed in but when driving at high speeds for about 1 minute the motor just stops, suddenly, like a kill switch. Could this be some sort of automatic shut-off? As low as this boat sits in the water the last thing I need is a sudden stop. oh, it starts right back up and isnt overheating.

 

[Clams Canino]

Re: 72 115hp merc stops like a kill switch

Got a voltmeter on it? That unregulated charging system can rise the 12v system up to 17+v - This can cause your ignition to do strange things. If that's the problem - drive with your lights on and the radio etc to use up the extra current available.

If that's not the problem - you have a thermal intermittant fault in the switchbox or trigger - likely switchbox. There is no auto shut-off except for the little mercury tilt-kill switch on the port side of the switchbox.

-W

 

[Alphabiatch]

Re: 72 115hp merc stops like a kill switch

So it wouldnt have anything top do with the fuel lines (people keep telling me to check for air leaks, dirty, etc.) or the rev limiter?

 

[Chris1956]

Re: 72 115hp merc stops like a kill switch

Alpha, There is no rev limiter on that motor. You might try pumping the fuel primer bulb at high speed to see if you have a weak fuel pump. if that doesn't help, it may be the ignition issue that Clams cited.

 

[croSSed]

Re: 72 115hp merc stops like a kill switch

I would be really surprised if this were a fuel issue. The fact that it suddenly just quits points to an ignition/electronic issue. A fuel problem would not do that. Even if the flow of fuel were suddenly and completely cut off, it would stumble along for a few seconds before complete shut down.

TG