Guys, its a 1992 Mach 1 endeaveor 290. Essentially a CC 260 stinger stretched about 1.5ft and then a 1.5ft molded platform. Anyhow, my port big block will crank and fire, but the starboard engine will only barely crank once then stop. Batteries are good and charged. The marina that had it, dewinterized it and claimed both ran smoothly... Its a dual battery system and I've tried all the switch positions. I know its not hydro-locked due to the motor turning over once. Drives are disengaged. Ground cable between motors is attached. Idea's??

I would put a big ratchet or a breaker bar on crank bolt and see if engine turn over easily first. It shouldnt take too much effort to turn it over if there isnt a bearing issue. If you feel crank bolt tighten STOP. Something is broke internally. If engine turns by hand check starter amperage draw. Should be about 100-120 amps.

Needs new starter.

Chris

Tow, she spins as a bbc should by hand... So I'm assuming nothing broken thats immediately evident. Will I blow my normal amp meter checking a starter?
Blueabyss, starter you think? Is it easy enough to swap that I can swap starters and make sure?

Depends on how much room you have.. Some boats require the removal of the engine.. I was not thinking about that when i told you the starter.. Might be worth checking the amps as suggested.

Chris

Check the ground strap and battery cable connections for corrosion or half broken wires before you pull anything

Just realizing I never updated y'all. It turned out to be a starter. It was a buddies boat and unfortunately didn't make it on the water, but she runs alright. Long straight pipes out the back and holy frak its loud.