No Low Idle Running

[bthorn1983]

fair enough. For others, as well as for my organization i would like to redescribe the problem to make sure i am as clear as possible, as well as to recap solutions.

- Bought the boat this year, it is a 2008 Maxum 1800 MX with a 3.0 Merc TKS 4Cyl.
- Checked everything out this year before putting it in the water, seemed good. Was told it was winterized by a guy last year. The boat was stored with about 2/3 of a tank, i do not know if there was stable put in the gas before storing.
- Topped off the tank with premium fuel, went to the lake.
- The engine will start for a bit, sputter and then stall out before being able to put in gear.
-Takes many tries, then have to get it to start and pretty much immediately put it into 3/4 throttle to keep the engine running.
- took the boat out and went around the lake at about 3000 rpms for about 25 mins, then when throttling down it stalls back out. Hard to restart, have to give it a lot of throttle to get it going again. This creates a very hard time when trying to dock as i have to come in hot and shut down.
- so far i have pulled some fuel out to see if there is water (no water fuel separator) appears there is no water in fuel.
- ran the engine without the spark arrester on, seemed to run ok but couldnt run for long without muffs.
- Trying to get this thing running good by this friday for Jobbie Nooner so i dont look too much like an amateur having to stall out and such when i pull up. Any and all Help is appreciated, so far im just trying to see what could have changed over the winter and trying to sort out the obvious so i dont HAVE to take it to a boat mechanic.

[mmwjr]

Originally Posted by shrew

@Mike. Do you know if these carbs use a pilot jet? This sounds a lot like a clogged pilot jet. This was the exact type of issue on my dirtbikes.

Other than the enrichment circuit which uses a temp sensor and solenoid to add gas when cold the rest of the carb is a standard 2 bbl.

[mmwjr]

Originally Posted by bthorn1983

well got some gas in a jar, let it sit over night, no separation. Also i do NOT have a water/fuel separator in line between my tank and my fuel pump. Any other things i should look at before i go buy a new solenoid for the TKS system? Also, i have a question, should the manifolds be drained of fluids? there are those two hoses that come up to the right of the engine, how often should those be drained?

The two hoses are to drain the engine and exhaust when winterizing the engine.

[bthorn1983]

good to know, so leave them be during the season? thanks

[mmwjr]

IMO since it will not idle even when warmed up if it is the TKS it would mean the circuit is not closing and running to rich, somehow I doubt this is the issue.

When winterized last was gas treatment used and was it ran to ensure it filtered all the way into the carb, if not gum may have built up in the jets.

A small vacuum leak can cause this issue.

Idle setting could be to low but should not have changed itself over the winter.

Use carb cleaner to clean the flame arrestor and let it dry before reinstalling it.

[bthorn1983]

MMWJR, thank you, those all seem like relatively simple things to try and correct, i will work on these things tomorrow and update. If anyone has any other suggestions please comment, other then that you guys have been and are awesome! i hope to have a trouble free boating day on friday and for the rest of the summer.

[mmwjr]

Originally Posted by bthorn1983

MMWJR, thank you, those all seem like relatively simple things to try and correct, i will work on these things tomorrow and update. If anyone has any other suggestions please comment, other then that you guys have been and are awesome! i hope to have a trouble free boating day on friday and for the rest of the summer.

Call me Mike

hope you resolve the issue soon so you can enjoy the season.

[Baby Blue]

vacuum is a good call. Definitely check the vacuum lines and also make sure choke is open. pick up some muffs and trying to keep it running while spraying carb cleaner in carb. could possibly need a carb rebuild.
I would give it a full tune up regardless. cap/rotor, wires, plugs, etc.
Let us know when you get it fixed. It's always good to hear what the solution is and helps others in the future.
Keep at it.. you'll get it going again.
BB

[mmwjr]

There are few to no vacuum lines on a boat however vacuum leaks can occur in a carb (bad gaskets), at the carb to intake, or intake to heads.

[Kevlar7r]

Vacuum leak on a boat engine is a bit of a misnomer, as for all intents and purposes, a boat engine doesn't develop vacuum (of any useable amount for operating accessories/systems). Useable vacuum is developed while the throttle plates are closed, and the engine is working to draw air around those plates. When the throttles are wide open, there is very little vacuum in the intake. This is because a boat engine is run with throttles wide open, so the system is open to atmospheric pressure, with no restriction (besides that of the intake passages themselves) to cause a pressure differential.



A better term on a boat engine would be an intake leak, as it is allowing air into the engine without going through the throttles. Since its not metered, it would lean out the engine mixture.

[mmwjr]

Since the OP issue is the boat will not idle the plates are mainly closed and engine vacuum will exists at this point, therefore a leak will cause a bad idle from being too lean.

Higher rpm your are correct which is why there is no vacuum advance on a marine distributor.

This reminds me of a friends 39' Ford that had vacuum windshield wipers, hit the gas and they stop.

[Kevlar7r]

Agreed Mike, I was just expanding on your comment about no vacuum hoses.



A friend of mine had a Karmann Ghia. The windshield washer was powered by the air in the spare tire.

[mmwjr]

Better yet VW had a gas fired heater option.

Man were old to know all this

[Kevlar7r]

Originally Posted by mmwjr

+1 back to helping the OP

And for the record I'm leaning towards gummed up carb and/or bad gas. May need to just go run it for a while, and flush some good gas with Lucas fuel system cleaner in it through the carb.

[bthorn1983]

Well guys thank you so much for your input. I got it out to the lake and it fired up and idled great until i put it into reverse, then it died out. Had to do the same thing, get it to idle then give it 70-80% throttle to get going, once out on the open water it drove great! No overheating (thank god! that was a scare) until we got out to the island, then of course going into a lower idle to creep into place for anchor and it kept dying. On our way back, mind you its about a 25 minute boat ride each way at near full throttle, she ran great. got close to the dock again and it actually idled pretty smooth until we got close then when i went to put it in reverse to adjust my approach it died out, had to manually get it to dock. Im thinking it will benefit from a good tune up, so far this year i have ran about a whole tank of premium fuel through it, so im ruling out bad gas and going with gummed up carb. I did get muffs and when i get some time this week i will fiddle with it in the driveway. We will get this thing running like a 2008 boat should run sooner or later haha! Thanks Again so far!

[mmwjr]

Try disconnecting the shift interrupt switch to see if the problem goes away. It is located on the shift bracket on top of the 3.0.

Do not leave it this way as it will cause wear on the dog clutch.

[bthorn1983]

Will try that, but it doesnt seem like an immediate shut off just trying to engage gears, it definitely seems like the engine is just dying out on its own when a load is being applied.

btw you guys were talking about vacuum operated things in cars, my 68 lincoln has vacuum operated everything! Also hydraulically operated windshield wipers, crazy old engineering haha

[mmwjr]

Yea I know the interrupt switch stumbles the engine only when coming out of gear, but if alignment or a bad cable this thing can get out of whack.

Just head stracthing and trying to eliminate a few things.

[Kevlar7r]

Running at speed doesn't pull fuel through the idle circuit in the carb. Check plugs, wires, rotor, cap, idle rpm, if nothing else wrong, might be worth getting the carb rebuilt.

[oldno7]

Was at Lake Powell last week, had the same thing happen on my 7.4 MPI.
Would start but quickly die out, attempting reverse.
I climbed into the engine compartment, had someone fire the motor,
Could hear a whistling noise--went to the air intake and it was plugged with dog hair.
removed all the fouling--fired it up and never another stumble.
Had me worried for a bit, though.