Engine Idle Surging Up & Down

[LuvBoating]

This is a 1992 Celebrity 200, 5.7L engine, Alpha 1 Mercruiser Drive (I/O). The carb has been rebuilt twice, both times in 2009. Previous owner had it rebuilt right before putting the boat up for sale, but did not tell us. After we bought it and was having new plugs put in/carb adjusted, mechanic recommended we have it rebuilt. The mechanic didn't remember that he had rebuilt this same carb two months earlier! Anyway, we still had somewhat of a problem with idling in Neutral after that, until I adjusted the idle up some and it was ok. Yesterday, after wife/I had been on the water and then tied up to a dock for a couple of hours, started the boat and the idle was again surging up and down some while in Neutral, but was able to underway and it ran fine. Got back to the ramp area, pulled the boat up to a dock, so I could get the trailer, and noticed (in Neutral) the surging going on again. Soon as some extra money shows up, will take it in for an evaluation and have the new distributor cap/rotor (came with boat) put on. May need a new carb.
Suggestions/comments?

 

[Bondo]

Re: Engine Idle Surging Up & Down

Anyway, we still had somewhat of a problem with idling in Neutral after that, until I adjusted the idle up some and it was ok.

Ayuh,... How High Up,..??

Much more than 750rpms, in gear, in the water, 'n you'll blow the outdrive by the time you replace the carb...

 

[LuvBoating]

Re: Engine Idle Surging Up & Down

Having a problem with engine running at the right speed (and smoothly) while in Neutral after returning to the marina after a couple of hours on the water.
What happened: pulled the boat into public docking (after returning from a ride on the ICW over Memorial Day Weekend), put the throttle in Neutral and the engine RPM's were pretty low (around 100 to 200). Had no problem running in Idle while going to the dock. Kept the boat running while I went and got the trailer (wife was with it). When I got back to the boat and the engine stopped, but was able to restart, put into gear/Idle and get the boat onto the trailer, but then the engine stopped again. Didn't need to restart. Still have a little problem starting the engine cold, but once it starts, seems to be fine when warming up to op temp. Have got a can of Prestone Carb Cleaner, but only sprayed the linkage so far. Don't know if spraying the inside of the carb will help our carb problem OR if we just need to take the boat into Service and have the carb checked out and possibly get a new one. Still frustrated with the carb!