Missfire or cough every now and then

[hlavery]

I have 1988 5.7 on ski boat Runs great but every now and then misses or coughs.
At high rpm will miss then keep going and run fine.
At slow speed like idly it will dye but starts back up quick.
New boat for me and have replaced Plugs, plug wires, dist cap, dist ignition sensor, coil and rebuilt carb.

We were out for 2 hours today and happened 3 times, twice at high speed once idleing in.
Thanks

 

[ryan04]

Even though you've rebuilt the carb it's possible that the fuel mixture needs to be adjusted. I'd check the plugs to see if any of them are fouling even though they're new. Make sure your flame arrester is clean as well.

 

[Fun Times]

Also you'll want to check your water separating fuel filter for any signs of water or debris and install a new filter.

 

[hlavery]

Thanks for posts,, Water separator is new and I drained tank 100 % and put in all new fuel.
I will try and check Arrestor today and check to see if any plugs foul.

 

[ihearth2o]

Check your oil too for gas or water contamination.

 

[hlavery]

Thanks again for post, I could not take boat out today but was able to check Arrestor and it is good. Oil also looks good.
I spent some time looking around and found ground wire from Ignition Modual to Distributer not connected. I connected it but cant test until tomorrow.
I will provide update.

 

[hlavery]

Tested today and same issue When running at 20 or 30 knots it will miss or quit then keep running.
Same at idle will just quit.

Dist. is grounded, new fuel, new fuel filter, Carb rebuilt and took out plug after quit but was dry. Disconnected Tack and still quit.
I had replaced throtle this summer so I disconnected wire to shift interupt and still did it.

I am thinking Ignition control module, please let me know if you think I am on wrong track?

 

[hlavery]

FIXED IT, It was loose wire on the back of the Tackometer. We tried bypass red to purple wires on ignition but still did it but we thought still could ground out. While at Idle we began taping on gages and shaking wire and found it!! This was hafter I went by local marine shop and they suggested looking hard at power supply to coil before purchasing ECM.



THANKS