Stalling issue fixed, surging continues

[liquidlew]

Update on question I posted for a bud with a 1997 Merc 5.7 Alpha 1 Gen 2 with a 2bbl Mercarb. It would stall throttling back to idle and surge while cruising below 3000 rpm. He had the carb rebuilt, no more stalling and gets right up on plane when he opens it up. However it still surges badly running under 3000 rpm. Still a carb issue? Or could his boat/model year have an ECU? I told him to break out his manual in the meantime, and I would try to help by posting here. Thanks guys!!!

 

[alldodge]

Update on question I posted for a bud with a 1997 Merc 5.7 Alpha 1 Gen 2 with a 2bbl Mercarb. It would stall throttling back to idle and surge while cruising below 3000 rpm. He had the carb rebuilt, no more stalling and gets right up on plane when he opens it up. However it still surges badly running under 3000 rpm. Still a carb issue? Or could his boat/model year have an ECU? I told him to break out his manual in the meantime, and I would try to help by posting here. Thanks guys!!!

Still sounds like carb. No mention of how it idles, so I'll take that there are no issues. Idle circuits are used just for idle rpm. It gets right up on plane and does fine but surges when you start going slower that almost WOT or hard at it. I would suspect the float level needs to be adjusted, probably down a bit. Guessing it may be getting a bit to much fuel.

On the other hand you may have a vacuum leak. If you have a gauge, put one on it and let us know what you find

 

[Bondo]

Ayuh,.... The carb was rebuilt,... Was the rest of the fuel system cleaned, 'n serviced,..??

Fuel filters checked,..??

 

[liquidlew]

I don't know about the fuel system (tank), but I did insist the first thing he needs to do is change fuel filters which he did. He said they found some crud in the carb filter bucket and jets were clogged when it was rebuilt. I also asked him about the plugs and cap/rotor and he said they are only a season old. He said the boat runs much better and idles good aside from the surging. I think all you guys are right that it's probably in the fuel/delivery system and I will mention that he should check for a vacuum leak. What about timing?