I have twin 440s in my boat (with Carter AFBs) and they ran great this summer. I run 1860 rpm all day. My question is, after a day's run coming into a harbor, my stbd engine would begin stumbling as if wanting to die. If I gave it a little higher throttle to keep it from dieing, I could still feel the stumbling/dieseling. RPMs would jump 620-680. If I left it at the same RPM as the opposing engine (530), it would surely have died. Has not done this in the past.

I should add; at cruising RPM, my rpm's would not fluctuate as they do when idling.

Carb cleaning?

Thanks

 

That's a good place to start. Also check the basics i.e. timing, vacuum leaks, fuel supply, filters. You definately want em running the same.
Is the prop free? No transmission right?

 

Whats better than a 440 Big Block?.....TWO 440 BIG BLOCKS!!!!!!!!! Grrrrrrr! Must sound great when you sync them up!

 

In the immortal words of 'Tim the Tool Man'....More power!

I'll check on the filters. I ran it today and it ran fine. Must have some crud in the fuel system somewhere.