1989 5.0 merc starts but no idle or acceleration

[JoDo]

1989 Maxum Cuddy 5.0 carbed mercruiser. Four barrel. I tested it all week, ran it over and over after sitting all winter with an almost empty tank. Everything ran fine. Had a stall issue when shifting to reverse so I cleaned and lubed the interrupt switch and fixed my problem there. Left for lake and put 20gal of fresh gas in. When at the lake, I backed off the dock just fine. When I went to accelerate forward it died. Then it would not idle either. I could rev the engine but the rpm's fluctuated. Whenever I tried to put in fwd it died. I was just about to flag someone for a tow when I tried "feathering" the throttle. I could creep it to the dock that way. I thought it was the fuel filter so I ran to the marina and bought one. This didn't solve it. Ended up loading it up and coming home. I wonder if the new fuel picked up some crap and sent it to the carb. I picked this up from a friend two years ago after it had been sitting unused in his yard for a couple years, I have never changed plugs, cap or rotor and don't know when he ever did. Thank you.

 

[searay3]

Re: 1989 5.0 merc starts but no idle or acceleration

start by giving it a complete engine tuneup. The stalling when shifting is a classic symptom of a worn lower shift cable. It is possible the carb may need work, but you won;t be able to determine that until the ign is right. If you haven't done it yet, you also need to pull the drive and replace the water impellor and check and lube the u-joints and gimble. Your gonna need a manual so post up a serieal number and someone will guide you to a manual for you engine and drive.

 

[JoDo]

Re: 1989 5.0 merc starts but no idle or acceleration

Thank you. Did the tune up: Cap, rotor, plugs and wires. Started, ran great in my driveway with the "earmuffs" on. Took her to the lake after work and launched. Ran fine, backed out, started full forward for about 30sec and she bogged right down. This tells me it's happening when the engine gets warm. I learned if I manipulate the choke plate by hand I could keep it running. So after talking to a mechanic buddy while tied to the dock, he determined it's a fuel metering issue which probably means a carb rebuild or at minimum a good cleaning. So I called another buddy to ask who could do this and turn it around by our camping trip this weekend. After giving me a name he told me to try this first: One can sea foam in the tank. Douse the carb really well with spray cleaner and let sit, start and blow the gunk out. Then while running pour one more can sea foam down the carb to see if I can knock what ever it is loose. I did this and she ran great, again, in my driveway. I let run for at least 20min and no problems. I guess we'll see tomorrow.