engine cuts in and out

[mcgee139]

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]

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?

 

[dingdongs]

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.

 

[mcgee139]

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]

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.

 

[mcgee139]

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.

 

[mcgee139]

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?