Yes u could do that.

dont mean to be a di@k,,,, but if you just had both motors out and replaced,,,, shouldnt all of that be new, and or cleaned while apart !!!!!!!???????

no no no, you are not being a dick. The engines were both removed by a local marina. the usual chop and hack. I am a Auto tech and he dropped off two bad complete assys. and two new longblocks. I just transfered everything... Did not know those were the grounding studs. and they look like crap. and i have replaced two ground leads they were so corroded. it partially sunk in florida. even the pans rusted through.

If thats the case u need to replace the whole wiring in that boat !!!!!!!!!

The salt eats thru the coper wires faster then u could replace them.
Been there.

last night wile installing stereo in boat with amp hooked to battery 2, no battery in one, I tried to raise trim tabs, they would not move but light on bilg and blower switch would come on, installed battery 1 and everything worked fine, I dont know what this means but I thought it was strange.

Last week had 2 motors on another boat that would not start 2 minutes after shutting off (yamaha 2 cycle boat). cleaned plugs, nothing, replaced plugs, nothing, then 2 hours later I found out there was no spark to either engine, turned out to be the lanyard, it was not pulled out but just enough to keep engine from firing

Ok, it was kinda bad ground... but now on the port engine everything is great. it turns on and cranks with the key and the fuel pump cycles and the alarm beeps once quick. the starboard will crank but there is no power to the fuel pump. but get this... the round connectors to each engine main harness. if i switch the port harness to starboard and the starboard to port the port still works perfectly. the pump will run and the alarm beeps. the starboard still does not. what could cause this? i swapped PCMs from engine to engine and no change. i checked everything. everything is hooked up and all my grounds are new and great. all of the power leads are new too. all re-located to the heads. (not the power leads) anyone know what im missing? Volvo poop!

Since you swapped harnes plugs from side to side and they problem did not fallow then you are looking at the wiring in the motor. If the boat went for a salt water swim then I would look VERY close at all the wire ends. They can look fine but not pass any voltage or current. My guess is you are still missing a ground some place or a wire is broken internally. Unfortunatly it is just testing wire to wire tell you find the problem. This is were a manual with a wire diagram would be invaliable.