Engine won’t idle

I have a 92 SN with a 351 and a Holly 4bbl. The engine runs fine at cruising speed but then dies when you throttle down to a slow speed or idle. Then it is hard to start unless you throttle up right after it fires. Any thoughts? Its really tough to dock at a fast speed!!

Dave

I tuned up the engine tis spring and there is only 364 hours on the boat.

Check the adjustment of your idle mixture screws.

Spray some carb cleaner down each side of the intake and see if you have a leak. If it idles up, you found the leak.

Since it just started two weeks ago, I'm much less inclined to blame it on the carb. It is an expensive part and you'll probably want to try some simpler stuff before you plop down that amount of money. There have been some good suggestions here already, and I'm sure more will follow in the morning.

The poor idle and hot stall issue with my 4010 went on for years and I just dealt with it. It can be hard on a transmission though. I had the carb rebuilt several times and even went as far as shipping it off to Holley and paid $325 to have it completely stripped, replated with the original finish, and reassembled with all new parts. The top pic is the 4010 when i got it back from Holley. Looks brand new; unfortunately, when I put it back on the boat it was the same old story: crappy idle/hot-stall. I'd spent that much money so I just lived with it a couple more years.

Last winter I found a thread about how bad the 4010 was; if I remember right, it was on this forum. I took a chance and bought the 4160 from Summit. Just WOW; what a difference. Now I crank the cold engine and hold it at about 1k RPM for about 30 secs and then drop to idle. The boat just sits there and idles, that was amazing to me. Then just put it in gear and it goes at 500 or so RPM without any further input to the throttle. For the rest of the day, it's just turn the key to crank, put it in gear, and it goes. No coughs or sputters; no more feathering and blipping the the throttle just to get the dang thing going without it stalling out. The sad part is that I'm so amazed that my boat actually runs like it should. I don't think I could tell a difference between the new carb and efi except for the starting procedure and somewhat better fuel economy.

I'm not saying the carb is definitely your problem, it could very well be something simple. I just wanted to share my experience and thought it might be relevant here.

I see very little reason to spend a lot of money to retrofit EFI to an older boat. A properly functioning carb can do the job nearly as well as EFI with a lot less cost and complexity.

Dave, what all did your spring tune up include?

Improper timing can screw up the idle as well.

Weak voltage at the coil can also cause this. With the ignition on, check the voltage on the post of the ballast resistor that is NOT connected to the coil and compare it to the voltage at the battery. Do the same with the engine running.

It's late... not sure if any of this makes sense. L8R, DKJ

My friend tried injection, he ended up putting the carb back on also