Fighting a miss under load
 

I have been fighting a miss most of the summer. It only seems to do it when the engines are under load. Ive switched msd boxes, distributors, and coils. Put new pick ups in the distributors. I have put new caps, buttons, plugs and wires. Rebuilt both carbs and switched them from one engine to the other. I even leaked both engines down and they checked out great. Im lost on what to do next.

https://youtu.be/LE8quU-Ef_k

Did you check for a lose wire?

Plug wire?

I see both tach dropping which eliminates all individual engine issues like wires or plugs. Does the boat actually loose speed when this happens and sound like its missing? If not I;d lean towards engines being electically tied together on positive posts and an alteranator issue in one engine. Hard to guess on the internet thou...

Doesnt sound like a miss on the video , looks like gauges have a bad ground.

Thought similar to you. The tachs don't jive with the engines either. Hard to tell by speaker quality of iPad however it sounds like the harmonics of a twin engine boat. Did you tap on tacks when their jumping around to see if the needle changes at all?

Check all grounds on engine and also one ground block behind dash panel.

I did a little digging since more often than not problems like this happen when someone builds bigger hp engines,and I see you have also.
http://www.offshoreonly.com/forums/p...dimension.html

Did you tune the carburetors for the engines ? You could be in a lean spot and causing this miss. I've run into this many times, as I'm sure many others.

Another MSD issue not talked about much is the rotor spring metal section (tongue) to dist cap button. Some rotors don't have this bent up high enough which causes a large air gap that makes it tough for the electrical energy to jump.

I switched the distributors before i took it out the last time. Prior to that the port engine was the only one that had a miss. When the port motor misses i can feel it loss a little power. I did not tap the tachs while running. It is hard to hear the miss due to the dry exhaust and the wind blowing in your face. I i guess ill check the grounds to the engine and to the tachs next.

I didnt change anything in the motors from last year. I was kinda wonder if have a transmission would have some kind of effect on the tuning if the carbs. At wot the port motor will run 500 rpm less than the port.