1989 Mercruiser 4.3 dies at idle

[mia9516]

My 4.3 dies at idle and idles rough. This happens on the water and in the driveway on muffs. I've adjusted the timing, fuel mixture, idle speed, changed spark plugs a month ago, rebuilt the carb last season, and replaced wires, cap, and rotor last season as well. I've read lots of posts tonight and the only thing I have not done is adjust the float from 14mm to 11mm. The boat runs great at wot and gets on plane fine. Temperature is within specs to @ 140°. I'm at my wits end and all of this is harshing my boating season mell...thanks in advance for any advice. Milton

 

[Fun Times]

Hi there, have you inspected the fuel condition for water or debris? May want to try running off of a external fuel tank to see if it helps any.

Also maybe the choke is out of adjustment.

Be sure to pull a spark plug or two to see if it looks rich or lean.

Just a few thoughts to start off with, hope it's an easy find for you, good luck.

 

[mia9516]

So I ended up adjusting the float to 11mm last night. I went to install the carb in today and the fuel line was cracked at the carb inlet. After a failed attempt at bending and flanging a brake line, I cut the original line after the break, splicing a 3/8" rubber line, and re-installed. My boat now runs like a champ. No more black smoke, no more dying at idle, and what's even better is that it stays running until I decide to cut it off. If anyone has a problem like me, adjust your float first! It'll save you tons of headaches. Happy boating everyone!