'94 - 305 slight surge at idle

[Calae 2000]

Took the boat down to the river Sunday evening. River was high an rough, so I chose to simply back it in the water and start it up on the trailer, with the goal of testing engine performance. I Let the engine warm up, put the motor in gear numerous times just to place it under a load. Ran fine. Only problem I noticed was in looking at the tach the motor was surging from about 600 rpm to 750 rpm. Was would cause the engine to surge up an down at idle ? I did just prior to running the engine clean the 4 barrel quadrajets small fuel filter. I also tried adjusting the idle mixture screws for smoothness. Runs good but not a perfect idle....... Feedback welcomed.

 

[Realmsteel]

I'm relatively new to boats and haven't tuned a Quadrajet in 30 years, but I would try adjusting the mixture again. It could be running lean.
With a Holley, I would always lean it out until it would just start to run rough and richen it up about a 1/2 turn depending on the engine.
Another thing could be the float adjustment, though with a Quadrajet, it's not as adjustable like a Holley.

Has the boat been sitting for a long time?
If so, did it do this before it was stored?
If not, then I would guess the carb is gummed up a bit and may be idling off only one side.

 

[NHGuy]

What carb, are you certain It's a quadrajet? Many are Webers too. Does it idle well in neutral?

 

[alldodge]

Took the boat down to the river Sunday evening. River was high an rough, so I chose to simply back it in the water and start it up on the trailer, with the goal of testing engine performance. I Let the engine warm up, put the motor in gear numerous times just to place it under a load. Ran fine. Only problem I noticed was in looking at the tach the motor was surging from about 600 rpm to 750 rpm. Was would cause the engine to surge up an down at idle ? I did just prior to running the engine clean the 4 barrel quadrajets small fuel filter. I also tried adjusting the idle mixture screws for smoothness. Runs good but not a perfect idle....... Feedback welcomed.

Probably the carb needs a good cleaning/rebuild and adjustment. If it's been a while since running it may smooth out but in most cases the idle circuit has some crud in it

 

[Calae 2000]

I'm relatively new to boats and haven't tuned a Quadrajet in 30 years, but I would try adjusting the mixture again. It could be running lean.
With a Holley, I would always lean it out until it would just start to run rough and richen it up about a 1/2 turn depending on the engine.
Another thing could be the float adjustment, though with a Quadrajet, it's not as adjustable like a Holley.

Has the boat been sitting for a long time?
If so, did it do this before it was stored?
If not, then I would guess the carb is gummed up a bit and may be idling off only one side.

I just bought the boat back in Jan from a dealer up in MIch. Was used last yr was the story. It runs pretty good it seems. I need to take it out and really run it to find out. Thanks for your feedback.

 

[Calae 2000]

Probably the carb needs a good cleaning/rebuild and adjustment. If it's been a while since running it may smooth out but in most cases the idle circuit has some crud in it[/QUOTE

Makes sense... Thanks.

 

[Calae 2000]

What carb, are you certain It's a quadrajet? Many are Webers too. Does it idle well in neutral?

Yeah am certain its a quadrajet. When in gear, and then pulled back to neutral the engine slowly comes back down to idle around 700 rpm. Takes a while for it to idle down..