97 4.3 merc. Phantom issues

[natsukau]

I have a 97 crest liner with a 4.3 merc. I am having issues with the motor stuttering and shutting down in rough seas at mid throttle. Motor runs perfect at low rpm and wide open. It will run all day in the river at mid throttle but as soon as I am in rough seas IE the Sf bay. the motor will start to stutter and eventually die. it will sometimes start after an hour or so but not always. I have replaced almost everything attached to the motor with new quicksilver parts and had the carb rebuilt twice. The only thing that I have not replaced is the icm. I have checked all grounds and connections. Removed the gas and dried out the tank just to make sure its not a fuel issue. Any insight is much appreciated.

 

[achris]

I also had a similar problem with my previous engine (a '94 4.3LX). Ran perfectly in most weather, but when the waves started kicking up, along came the phantom shutdowns... I tracked it down to wet electric connections, around the shift interrupt switch... Just a thought... Might help...

Chris........

 

[Scott Danforth]

First though is shift interupt switch or engine kill lanyard

 

[natsukau]

Thank you guys for your input. I have checked for wet and loose connections and can't find any. There isn't a lanyard on the engine kill. Could it be a faulty shift interrupt switch?

 

[Scott Danforth]

just because the lanyard isnt there on the kill switch doesnt mean the switch isnt bad. jump the two terminals on the back of the kill switch and go for a ride.

 

[Mad Props]

Sounds like an electrical issue to me... Try connecting a multimeter to the coil terminals in continuity mode and lightly tap on the coil with a small wrench or rubber mallet and see if you can cause an open circuit, then move the positive lead to the top terminal on the coil and do the same thing... There could possibly be an intermittent open in the coil...
Not likely but outside of the shift interrupt switch, kill switch, or just a bad connection, can't really think of anything else.

 

[natsukau]

Thanks guys, I bypassed the lanyard kill switch and found a wire tapped on to the coil wire. The previous owner wired an hour meter to the coil wire and used uninsulated connectors. It was not mounted and flopping around the engine compartment. Maybe the coil was grounding out with all the bouncing around in rough seas. I dont think its a bad coil because i already replaced it and still the same problem. I'm going to test on tuesday in sf bay hopefully the problem is gone.

The only thing I haven't checked is the shift interrupt. How do i check to see if its faulty?

 

[achris]

...The only thing I haven't checked is the shift interrupt. How do i check to see if its faulty?

Disconnect it. Just be aware that shifting will be difficult, may have to do it by shutting the engine down..

Chris........

 

[natsukau]

So I got the gremlin out of the motor finally. All my issues were due to a going bad oil pressure fuel pump cut off switch. Thank you all for your help...