1994 Mercruiser 3.0 running smoothly but dies on neutral or low gear

[dlogvine]

I am working on my 1994 Maxum with 1994 Mercruiser 3.0 two barrel carb. It is running smoothly when a little gas is added by pushing the throttle but starts choking when Im switching to low gear and dies on neutral. I looked at the carb, Mercarb, and used some carburetor cleaner. It looks pretty clean in the barrels but it might be dirty inside or might have a dirty filter. Should I rebuild it with a new rebuild kit or is there anything else I could do prior to rebuilding? Thank you

 

[QBhoy]

Check it’s not getting water back into cylinders from exhaust/risers. Pull the plugs and check for signs of water. That would sure do exactly what you describe.

 

[Scott Danforth]

pull the carb apart, clean the idle circuits. there is no mechanic in a can. check the content of your water separating fuel filter to make sure you only have pure fuel ( replace the filter)

 

[Weathersbytaylor]

Gonna mention to try bypassing your shift lock interrupt switch and eliminate that as a potiential culprit since your having issues around the coming in and out of gear portions of the throttle.

 

[fishrdan]

The carb probably needs to be rebuilt, but I'd adjust the idle mixture and idle speed adjustments before tearing into the carb.

Before adjusting the idle mixture, count how many turns it takes to lightly seat the mixture screw (1 1/2 turns, 2 1/4 turns?, etc), so you know where it started at, then back it out where it started at. If you have to rebuild the carb, you'll have a good ballpark starting point for idle mixture. I've rebuilt my carb 4-5 times (ethanol.....) and my bench idle mixture adjustment is almost spot-on, since I know where my boat's carb needs to be adjusted.

Does it idle normal while in neutral, and only have problems shifting in/out of gear, or run bad all the time. The engine dying while shifting is most likely the lower shift cable

 

[dlogvine]

The carb probably needs to be rebuilt, but I'd adjust the idle mixture and idle speed adjustments before tearing into the carb.

Before adjusting the idle mixture, count how many turns it takes to lightly seat the mixture screw (1 1/2 turns, 2 1/4 turns?, etc), so you know where it started at, then back it out where it started at. If you have to rebuild the carb, you'll have a good ballpark starting point for idle mixture. I've rebuilt my carb 4-5 times (ethanol.....) and my bench idle mixture adjustment is almost spot-on, since I know where my boat's carb needs to be adjusted.

Does it idle normal while in neutral, and only have problems shifting in/out of gear, or run bad all the time. The engine dying while shifting is most likely the lower shift cable

The engine dies in low gear, when not much gas is getting into the carb. It has no problems with the shifting. I think the boat was sitting for a while in the storage before I bought it (Im replacing all the decking and some stringers) so most likely it is the carburator that is at fault