Changed a few things wires, coil, headers, plugs, and electric fuel pump.

Swapped carbs no change.

Runs good at 1,250 and above under that it dies. If I pull it back to idle it quit if I slowly pull it back to idle it stumbles and dies.

No connection with drives imo
both were ok lets say last year? It started for both at the same time?
need more info to try to help you!

Ck fuel psi and charging system at idle.

Check or adjust points? those need replaced at tune up time also....

Swap carb no change. I assume 2 engines? Carb idles on other engine, both carbs won't idle on this engine? Bad vacuum leak.

Yes twin engines.

have you double checked the firing order after changing the wires, vacuum leak ? what's the fuel pressure

Could be trash in your carbs. I have had one of boats not idle and die like that but would run ok with more rpm. Ended up being trash in the jets.

I think both carbs run good on the other engine, and both won't idle on this engine. Makes me think vacuum leak cuz engine is ok under power. Check if it has pcv and broken hose. Otherwise intake manifold gasket.