370 Da Port engine rpm drops at cruise speed

[Nauti-Kal]

Has anyone else experienced this? As I'm cruising at 3200rpms the port engine rpms drop 200-300rpms so I throttle up on the port, a few minutes sometimes less the rpms rev up 200-300, back and forth, up and down....sometimes won't happen for 30-40 minutes, at times it happens often! Scratching my head.
I've had the carbs rebuilt since this started but did not help.

 

[kap2]

Are the engine's RPMs actually dropping or could this be a tachometer issue? You can try cleaning the electrical connectors contacts to ensure good connections. Also, if you haven't replaced fuel filters it might be changing them.

 

[Nauti-Kal]

You can hear the change in tone with the port motor and the fuel filters I checked by pouring out the gas in a jar to see if there was any water in the filter separator. I think it maybe the mechanical fuel pump that's attached to the raw sea water pump! I had issues yesterday with port engine not starting, pulled off the fuel line from the carb and cranked the motor and zero fuel was spewing out. Thankfully I was only three miles from home port and docking was no fun with only starboard engine.

 

[kap2]

Glad you got back in safely. Sounds like you might have found the issue. Let us know if the new fuel pump solves the RPM issue too. Good luck!

 

[Jeff6566]

I had the same problem, turns out just tightening the throttle lever solved it. Carb spring pulling it back..