Ta12sec

iTrader: (1)

My boat has twin 5.7 mercruisers in it. Engines have 500 hours and run strong. Except the starboard engine when it's hot it doesn't want to idle and will die under 1000 rpm. Really not fun when docking and loose power steering and one engine. I did plugs, wires cap rotor and a coil and no change once it's warmed up it doesn't like to idle. I'm looking at pulling the carbs and having them rebuilt anything I should be checking before I do that?

Brandonb_05

Timing.

Unlimited jd

iTrader: (5)

Most likely debris in the idle circuit of the carb. I've yet to see timing move itself unless something else is wrong.

Brandonb_05

Yea that was my thinking as well. I would check it just to make sure, it only takes 5 minutes.

Unlimited jd

iTrader: (5)

Never a bad thing to confirm.

Bondo

Ayuh,..... Sure sounds like plugged up idle jets in the carb,.... A Rebuild will confirm it, 'n fix it,...

Check the Contents of the fuel filters for clues,....

Did ya check the timin', when ya replaced all the ignition hard parts,..??

FIXX

iTrader: (2)

what lil red said..try this first...get some card spray..disconnect the throttle from the carb..start it and rev it by hand,,spray some carb spray into the carb until all the belt material is gone..yes the fan belts ware and get sucked into the carbs and plug chit up..ok now rev the engine to 3 to 4 k and snap the choke shut,,this sucks the crap out of the idle circuits..when you snap the choke shut you also open the throttle further to keep it running to try to keep the rpms up when doing this and open and snap the choke shut several times when revving it up..you will see a lot of black smoke coming out of the exhause so make sure your out in the open..it usually works for me..

F-2 Speedy

iTrader: (6)

Did I miss something or did the OP say it only happens when its HOT, Im not a carb guy but it sounds like its trying to Vap the gas in the bowl, starboard engines being Carb or EFI seem to have issues in hot & high humidity days in a lot of cases

Drew555

What about bad manifold or headers. Have you pulled your plugs? If you rev the motor up does it clear up for a short while?

Ta12sec

iTrader: (1)

I have not checked timing but next time I go down there I'll bring a timing light but the engine runs strong off idle so I don't think timing is off, I also haven't done the carb clean thing, I'm scared to do it on the water and feel bad doing it at the marina. The boats new to me I've only put 5 hours on it they may be original, rebuilding the carbs wouldn't be the worst thing in the world. Bad manifold, that's actually possible the starboard motor does have a small water leak though the casting on one manifold. I have the new manifold that's Saturdays plan Don't see how that would cause stalling. Guess I'll try the carb clean on the water after the manifold and if it still stalls after I'll take the carbs with me and have em rebuilt.
I'm new to gas powered boats just wondering if I was missing anything obvious.