Re: omcto mercruiser swap
You could probably use the OMC harness. Depending on the year there may be more pins in the Merc harness.
I used the Merc harness in mine because I wanted to rewire the boat anyway.
The Cobra engine harness might work but you'll have to remove the ESA and rewire it anyway. I would completely rewire the engine if you don't have a usable Merc engine harness.
You'll need to use the Merc trim pump. (you might be able to use the OMC pump but I wouldn't waste my time trying to make it work)
Also, take the time to clean up the engine compartment and maybe splash a little paint in there.
Here's a before and after picture...
I've posted these pictures so many times I think everybody is getting tired of them
Before
After