2001 Mercury 9.9 2-stroke keeps stalling - help?

[LutherDLG]

Hey All,

My buddy and I took his family's old fishing boat out yesterday and the motor kept stalling out when we were trying to troll. The motor hadn't been started in 7 years, but was well maintained. We changed the lower leg gear oil, cleaned the spark plugs and fogged the cylinders the night before. The carb was extremely clean and the fuel filter looked fine. When we were full throttle it ran fine, but would stall out after a minute or two when we slowed down to troll. All I can think of is weak fuel pump - would that makes sense? It seemed like it just wasn't eating enough fuel at idle. The fuel mix was fine, etc. We didn't check the water pump or impeller, but would that cause stalling issues?

Any help is appreciated. If this should be moved to general discussion, please let me know.

[oilngas]

the first thing I would change would be the fuel (use fresh non ethanol if u can get it) as well as the fuel line, maybe ethanol fuel ate up the lining and somehow it passes lot of fuel but not a little.

[harrydude]

I would check fuel lines for good connections and for sucking in air .... Also check fuel filter

And the most forgotten on 'is the vent on fuel tank open'?

[LutherDLG]

Interesting - didn't think of the lines. We cleaned out the fuel bowl and got fresh fuel and new oil. It was still doing it after hours on the water and would run fine with throttle, so I kind of ruled out any bad fuel still being in the system, but I never considered the lines.

[LutherDLG]

And yes haha, the vent was open. It wasn't at the start, but we corrected that one pretty quick!

[alltoys]

You have carbon in the cylinder take the spark plug out spray in some carb cleaner in the cylinder let it sit overnight. Start it the next day run it till it cleans out that should be enough if not repeat one more time.

[Tom Pullings]

Does it idle in neutral?

[Habfan]

Get new spark plugs !!

[spurly]

Mix a couple ounces of Seafoam, in with your gas, new plugs, and maybe adjust your idle, just a smidge.

[Kingfisher]

I'm with Spurly on this one. Seafoam, Seafoam, Seafoam. Even if you get it running run some of that in the fuel. It will help any small motor not gum up.

http://www.ipdusa.com/uploads/images_products_slideshow/fullsize_5993.jpg

http://seafoamsales.com/

[Kingfisher]

The more I think about this, the more I think it could be a fuel pump issue. Or a cracked fuel line letting air get in the system. The fuel pumps are really easy to rebuild.

You may also need a carb rebuild.

You can get all the parts shipped to you from http://www.boats.net/?gclid=COHpi9S8tMYCFUFufgodDR0E7w

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[Kim473]

Seafoam, new premeum gas, fuel filter, new plugs, check fuel line for cracks, if this all fails then fuel pump and or carb. May be just carb adjustment. My guess is carb needles and seats just gumed up slightly.

[-JR-]

Can you restart the engine right away after it stalls,or do you have to wait 10 min or more.

[nast70]

What oil/gas mix were you using?
I have a similar motor but much older with the opposite problem, idles good but stalled when you gave it gas. I mixed 35:1 and think i may have mucked up the math for the mix ratio. But that being said the tank and fuel line are old too, the bulb gets soft after a while so i might have a bad line too.

[CanuckShooter]

Are the coils good? Check all the connections for corrosion.

Nast70~~my old merc idled good but would stall giving it gas to speed up...was a bad coil causing the problem.

[Tom Pullings]

Even though the carb looks clean it would still be wise to take it apart and clean thoroughly. Possibly a carb rebuild kit. The jets are super tiny and they can quite easily get gummed up.

[LutherDLG]

Thanks for all the tips, Guys.

Yea - I thought it was strange, but it would idle fine in neutral. It was stalling out when we slowed down from plane to troll. We figured out that it would stay running longer if we squeezed the fuel hose ball a couple times every minute or so, which made me think weak fuel pump.

I'll probably knock off a couple of these things - like the Seafoam and new plugs,
Etc. but wait until the end of the season to tear his carb or fuel pump down. The coils idea is also interesting, I didn't think of that. But that definitely happened a couple times - would stall out once we put it in drive and give it some gas.

Thanks again - any more ideas keep letting me know!

[trouty]

sometimes it's far simpler than you think. Try a new fuel line, I had similar issues lately and that was it. There are check valves in the bulb that get worn out. New hose and issues gone.

[Rick.]

Go to the mercury forum at Iboats.com
Some one will give you some help I'm sure. I'm not that familiar with Mercury but it sounds like the carb. needs a thorough cleaning to me. If it runs well at high speed I would think that rules out a lot of things mentioned above. There is a slow speed gas path and a high speed gas path in OMC carbs. Sounds like the slow speed could be plugged. Best of luck. Rick.

[huntsfurfish]

Get new spark plugs !!

^^^^^^^^^^^^^^^this^^^^^^^^^^^

[dutchman]

First thing I would look at is the carb. Because these toys don't get used a lot, our crappy gas evaporates and leaves behind residue to plug off the pilot jet which runs the idle circuit. The pilot has tiny holes that plug real easy. Usually you don't even need a kit, just remove the jet, clean and reinstall. Happens all the time to carbed sleds, bikes, lawn mowers, etc.
If you can live with the stall, try the Seafoam first. It does wonders and if lucky, cleans this up with out removing the parts.

[Kokanee9]

First thing I would look at is the carb. Because these toys don't get used a lot, our crappy gas evaporates and leaves behind residue to plug off the pilot jet which runs the idle circuit. The pilot has tiny holes that plug real easy. Usually you don't even need a kit, just remove the jet, clean and reinstall. Happens all the time to carbed sleds, bikes, lawn mowers, etc.
If you can live with the stall, try the Seafoam first. It does wonders and if lucky, cleans this up with out removing the parts.

As mentioned several x previously, try the seafoam first. Do not over mix it by adding too much to the gas. After adding the proper amount, make a bunch of runs around the lake to loosen up any gum or varnish. This may take up to an hour or more.
You will know when the lines and carb are clear by proper idling.

Using premium gas is also a must, as well as visually inspecting the inside of the gas tank for any sediment in there.

The fuel line should also be drained by pushing in the check valves at each end and holding it at an angle to drain out. Drain the fuel line into a glass jar or something similar and inspect the gas that came out for anything that shouldn't be there. Drain it before adding the fresh gas and seafoam.

Double check your fuel/oil mixture. I believe 50:1 should be right.

[Kokanee9]

sometimes it's far simpler than you think. Try a new fuel line, I had similar issues lately and that was it. There are check valves in the bulb that get worn out. New hose and issues gone.

Also try and remember if the priming bulb was sitting level when you were on the water. They are designed to work while sitting level.

[Kokanee9]

Another thought is to try putting the old plugs back in unless the new ones are the exact same as the new ones. (Brand and spark plug #.)

[Kokanee9]

Coil will be suspect if it is running on one cylinder when trolling. You will hear the second cylinder cut in as the rpm's increase.

Not sure what else to try, but if I think of something, I will post again as I have been.

[Kim473]

I had a small crack in the primer bulb once and had similar problems in the past, sucking air rather than gas. Also, is it a old metal gas tank? Rust in it pluging stuff up? Had that problem too. Flush it out. Do the cheap simple things first.

[LutherDLG]

Thanks so much for all the input.

We should be back out in the next couple weeks, we'll take care of a few of these smaller items and i'll report back!

[Big Red 250]

Check the rubber O rings in each end of the fuel line connectors. One at the motor and one at the tank, they could be dried out or cracked from sitting for 7 years.

[dgitz]

I had this issue with a boat once. Would run for a bit and then die. Let it sit for a while and it would start back up and then same thing. What it turned out being was all blades on the impeller in the water pump in the leg busted off so it was overheating. Must have sucked some crap up. Replaced the impeller and she ran like a dream again.