Anyway to check Voltage / Amperage of the ignition? Are you sure the ignition is holding up on both sides at WOT?

That's why I suspect coil vibrating in boat and not dyno, or a wiring issue in my harness maybe that we didn't see on dyno, we did not use plug we wires ignition direct to dyno, I checked voltage running at idle, no way to really check under way at WOT... Ten again I can probably wire a volt gauge to ignition for temp use and have someone watch it... Hmmm

I am tonight and test this weekend I never messed with that dice they were same on dyno,!but I am thinking vibration and waves could make it act up and that is not the case on dyno, so yes I was swapping them tonight ..

I meant to touch on same thing earlier and then forgot. is it possible to run both engines off both battery's.

If you've cked everything mentioned as it sounds like you have I would almost have to think its past the engine. Not a water pump or alternator seizing up or any other belt driven accessory? Again just thinking out loud.

Right I really have addressed nearly every possible thing, the coil idea just came to me yesterday, it's really seems to something that shows up when in boat not on dyno, I also dynoed with sea pump and alternator charging and engines still 1 hp apart. Like I said it's been down all last summer and all this year... Really annoying since it wasn't when I first put them in boat I saw full rpm just a few times... The rest it's always lagged over starboard

Has to be a really fukked up issue that's obviously hard to figure out... Ugh

No water pumps, no power steering just alt and sea pumps.

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Do you see the RPM difference from the start, or does it gradually show up as you run the motors, heat up, WOT ...

move the beer to the other side of the boat.

Seems ok to 2500 ish then I notice lag

Lolol