Runs on high rpm but dies on lower rpms

[Don O'Gorman]

I have a 1992 MerCruiser 3.0L Alpha One in a 1985 Sea Ray Cuddy cabin. My issue is I recently had it in for a throttle shifter cable replacement. The mechanics said when they tried to start it, it would start but then die soon after. He said he made an adjustment to my mixture because he thought it was running too lean or maybe rich...I don't remember but I thought it weird because at the end of last season the boat was running as good as it ever did. Apparently I forgot to put stablizer in the gas for the winter and my little filter near the carb was all gummed up. I pumped out the old and put fresh fuel in it today but when I went to run it with the muffs on I could get it to run at pretty high rpms albeit a little rough but when I tried to back the throttle down it would die on me. I removed the fuel line near where it goes into the carb with a towel under it and the towel was wet with fuel so I am assuming my issue is not the fuel pump. Or could it be? Or is my problem that my idle and mixture is out of adjustment from that mechanic fooling with it? Or someone suggested that maybe I have a vacuum leak or do I need a carb rebuild? Any thoughts or advice is appreciated
Don

 

[Lazy Daze]

If the filter was gummed up... likely the carb is as well. Rebuild. It's NEVER a bad idea to clean and inspect a carb.

 

[Skybolt]

The primary side, low speed jets are clogged. As Dennis said, time to rebuild.

 

[Don O'Gorman]

So how complicated is rebuilding a carb? Is this something that the average boat DIYer able to do or do you need some in depth knowledge of carbs to accomplish this? Can you recommend a kit that won't break the bank and comes with step-by-step instructions?
Thanks

 

[Creekwood]

So how complicated is rebuilding a carb? Is this something that the average boat DIYer able to do or do you need some in depth knowledge of carbs to accomplish this? Can you recommend a kit that won't break the bank and comes with step-by-step instructions?
Thanks

Its not hard but setting it back up and getting the jets adjusted right can be a bit tricky. Lots of Youtube videos on it, so you could watch a few and see if you are up to it. Getting a mechanic to fix your mess if you screw it up might be more than just getting it done though.

 

[Don O'Gorman]

Any suggestions regarding which kit to get? And when you say " getting the jets adjusted right" are you referring to adjusting the idle and mixture once the carb is reinstalled?

 

[Creekwood]

Any suggestions regarding which kit to get? And when you say " getting the jets adjusted right" are you referring to adjusting the idle and mixture once the carb is reinstalled?

Yes, adjusting the jets. There is a starting point guidance, but it will need tweaking to run right. Get the kit that is for your carb model. If its OEM you can punch your engine serial number into Mercruiserparts.com and look up the part number.

 

[scoflaw]

Simple to do set the float height and adjust the idle mix screw.