Thanks Chris
Brand new Odysseys and they are fine. Going to switch it back like it was. Just thought it was interesting that one single ground change like that could cause that much draw...
Dave

so was it ever determine where the power lead was hooked for the tilt / trim ?

Also engine back side ground cable installed from (studs) one engine to the other engine is a normal install. This cable needs to be spec sized and the same size as the ground cable from the battery to back side of engine ground stud.

But also make sure and always install a proper size ground cable(s) from the starting battery to back side of the engine stud . Make sure all is clean, rust free and tight.

All ground cables need to be of spec sized if not they will cause a voltage drop. And the goes for all positive cables. All cab;es need to meet the correct spec size - all sizing is determine how long the cable runss are. The longer the runs the larger the cables need to be. This is ABYC speced as well.

If all cables are clean and tight - the next cause for voltage drops is the wrong size cables themselves. To small always causes voltage drops.

Found this for reference for whomever.

USCG just like I mentioned

page 24 and on ---- even refers grounding 2 engines together in which I mentioned is normal - and that cable needs to be the same size at least as the battery ground cable. But again that cable needs to be the correct size as well. Same goes for the positive cables Sizing diameter is important

https://www.uscgboating.org/regulati...ELECTRICAL.pdf

PAGE 25 has a good reference diagram of what I was trying to make clear.

Update
 

Took the boat for a ride this morning and seems like the problem turned for the worse now it pops holds back at 4700 RPMs without touching anything left (port) engine. Hands off the trim.
Tonight going to disconnect stereo amplifier and swap carburetors also check Perko switches for corrosion tightness excetera.

ignition rev limiter ? If applicable for the exact MAX Volt set up that is installed ?

I don't know if they have rev limiters...Hardin-marine ready to run. Timing is locked at 34.. no advance. We also swapped distributors and it still does it

That would be a kick in the nutz. LOL. Not uncommon for rev limiters to start dropping cylinders before the rpm value set. ON MSD's and others. I set the rev limiter at least 800rpm higher than the max rpm the engine is going to be run at.

I didn't read the whole thread, Did you do a compression test? how do the plugs look and is there a difference how they are now.

These engines are brand new 10 hrs maybe. Not rebuilts http://www.1800runsnew.com/new-base-......502(8.2L)LH 435 hpGen VI Roller Camshaft
High Output Rect. Port Heads

3 weeks ago it ran great until we hit a wave??

Oh crud 1800 runs new, they have changed names many times and I had an issue with one of there motors years ago