Spit & Sputter - Maxum Boat Owners Club

spydermann22 · 04-19-2015, 02:45 PM

Hi guys, I have a 2000 23 SC, 5.7 Alpha, 2bbl. Carb was rebuilt by a marine mechanic, installed by myself and mechanic friend 2013. It purred after this and ever since. on our final outage last fall the engine started to spit sputter and kill while idling in gear, barely keeping itself going while in neutral.
I got the boat out of storage yesterday and ran it with the hose hookup. It fired right up and idled for about a half hour, running very well. I then took it to the lake where the spitting & sputtering immediately started. It runs like a top as soon as you can get it into gear and get a little gas flowing but this isn't an easy task, especially at a busy dock.
Any help is greatly appreciated.

Phillbo · 04-19-2015, 04:43 PM

Pull the fuel separator and pour the gas into a glass jar. let it sit overnight and see if you have water in the fuel.

mmwjr · 04-20-2015, 01:11 PM

So you are saying it has a bad idle but once accelerated either in or out of gear it smoothens right out, correct.

What rpm is it idling at? Could be a small vacuum leak or an issue with the idle circuit of the carb. Checking the fuel for water is not a bad thing either.

spydermann22 · 04-21-2015, 06:19 PM

gas looks good, no separation at all surprisingly..
Idle was around 800 RPM.
I will have to check it out for vacuum leaks. I did replace the intake manifold last year due to it leaking (posted previously). I did purchase factory gaskets from the local Marine store.
I also found a male spade (wire connector) that I can't find a home for. I will take a picture of this to see if anyone recognizes it and can tell me where to stick it.. ;-)

mmwjr · 04-21-2015, 09:48 PM

rpm is a little high and should be about 650 rpm.

Yep I remember your woes last year.

oh we can tell you were to stick it

Phillbo · 04-22-2015, 01:55 AM

Loan wire connecters are not uncommon. They use the same harness for all possible options and if an option is not selected the wire just goes unused.

spydermann22 · 04-27-2015, 02:59 PM

Well, Sunday I finally was able to work on the boat. I started in the driveway with muffs again. This time it would hardly run at idle, it was really a chore to get it to run long enough to give it a little gas to keep it running.
I used Carb & Choke cleaner to search for any vacuum leaks, spraying around the base and all of the gasket areas but couldn't find anything. I then ran the engine up to about 2000 rpm and sprayed the carb cleaner all around inside the carb using the red straw and really focusing on the jet areas. After this the engine would idle but very low and rough. I then turned to the idle adjustment screw. I marked it's position 1st then turned it out maybe a 1/16th of a turn and it seemed to smooth out. I then shut the engine off and turned it all the way in to record how many turns out it was (1-3/4 turns from bottom). I put it back to where it was (before I messed with it) and it would idle but again low RPM - not a smooth idle. I turned it out to the 1/16th turn beyond the starting point and it seemed to smooth out again. At this point the RPM was right at the 650 RPM - maybe a hair below.
I headed to the lake stopping for boat fuel and added a can of additive (seafoam - delete this if you like, this isn't a plug but is a preference). When we hit the water the engine idled, seemingly rough but running. It would idle up and down a hundred RPM or so, up to 650, then down, then back up. We decided to Idle around and drag some crank baits for a while to have some fresh gas and additive run thru the idle circuit. We continued this for about a hour. After this the idle wasn't glass smooth but very much improved. After a couple of hours of regular use the idle did seem to smooth out, when we left it was very smooth.
The boat didn't sit for any length of time last year, we used it a lot after July 4th, using it at least every other weekend. I guess our usage would have thinned out towards fall but I wouldn't think the boat sat anywhere near long enough for the gas to gum up. In any case I am hoping this was the case and running the additive has dissolved the interference.
I am hoping the issue is resolved.

mmwjr · 04-27-2015, 04:56 PM

Idle should be 650 rpm and less and it will run rough. Sounds like the carb may of had some gummed up passages.

Have you checked the based timing?

spydermann22 · 04-27-2015, 06:22 PM

I had my mechanic buddy check the timing earlier last year. It was set right, we hadn't moved it..
I am hoping you are right Mike, I appreciate your guys' help!
Keep up the good work..

Kevlar7r · 04-27-2015, 06:41 PM

Have you pulled and checked the plugs? I find I go through plugs about once a season. Pay attention to any signs of rust on the plugs, could mean water intrusion.

I had an experience with an older boat where a stuck-open thermostat made the engine perpetually run cold, and it ran rough until I really got it under load. Couldn't hurt to check the thermostat.