engine cuts in and out

M

mcgee139

Cadet
Joined
Jun 24, 2012
Messages
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Hello I have a 1990 4.3merc. when driving say around ? throttle, their is a sweet spot were if I leave the shifter in that spot it sound like the engine cuts in and out every 30sec or so(cutting power to the engine) could I have a bad shift interrupter? If I move the shifter a hair forward and backwards it will not do that. Can I bypass the shift interrupter to test it? If so what wires do I disconnect or connect together?
Thanks
 
NHGuy

NHGuy

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May 21, 2009
Messages
3,631
Re: engine cuts in and out

That won't check it. The shift interrupt is needed to get the drive into neutral. Does your cutout happen at the exact same rpms each time, or is it more of a load dependent thing? Does the boat run well at higher speeds than the problem one? Which carburetor do you have?
 
D

dingdongs

Chief Petty Officer
Joined
May 29, 2009
Messages
649
Re: engine cuts in and out

take a photo of your shift interruptor and post it.there should be a setting on it and maybe vibration is tripping the microswitch.a photo will be required but should not affect the ignition until changing from gear till neutral.
 
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mcgee139

Cadet
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Jun 24, 2012
Messages
7
Re: engine cuts in and out

Hi thanks for thge replys, It happens around the same rps everytime im not sure what carb I have all I know at this time is a 2barrel card.

I will take some pics tomorrow morning and post them.
 
NHGuy

NHGuy

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Joined
May 21, 2009
Messages
3,631
Re: engine cuts in and out

Well if it always happens at the same higher rpms I'd check the timing and the ignition stuff like wires, plugs, sensor, cap & rotor. The controller increases the timing advance based on engine rpms. Maybe there is something going wrong at that advance value.

If you can run the motor faster than the trouble speed, what I said is less likely.
 
M

mcgee139

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Joined
Jun 24, 2012
Messages
7
Re: engine cuts in and out

I have already checked the plugs and regapped them(all good), It looks like new wires, cap and roter looks good. I checked the timming it was at around 10-12deg brought it back to 8 deg. not sure what sensor to check.

It is weird it only happens at the same spot all the time if i go on either side of that spot it runs perfect. trying not to spend a lot of money at the end of the seasion.

Thanks.
 
M

mcgee139

Cadet
Joined
Jun 24, 2012
Messages
7
Re: engine cuts in and out

Just to give a update. I ran the boat the hole day with out the shift interrupter and had no issues so I either have to re adjust it or replace. how do you adjust it?
 
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