problem after stopped for 10-15 min

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rewinder

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I have a 2001 Merc 2 stroke. Always starts 1st or 2nd pull after normal cold start prime routine. runs just fine, and runs full throttle like it should.

i can stop and start it, fine, but if I wait 10 to 15 min, it will bog down on acceleration, but will run at idle the way it's supposed to.

Bulb seems to not be as firm as when I pump it to 1st start it, but firimg it up does not make it accelerate normally.

the only way to rid this acceleration problem, is to pull the primer button out a few times, while trying to accelerate, it catches, and will power up normally.

Again, if I start it within 4-5 min, there is no problem, only if i fish for a bit and then start it.

does this sound like a weak fuel pump problem?? or an air leak??

I'm baffled
 
Sounds like you hit the nail on the head. Having to prime it to get it going a fuel delivery issue. You said it runs fine after you have prime it, so I don't believe it is a carb issue.

Sounds like you may want to investigate your fuel line and fuel pump. If you can, to use a known good hose and tank. Sometimes, with age the hoses can crack and allow air in the line along with the fuel. The fuel pump is great for pumping fuel but has issues with pumping air.

If the external fuel line is not the issue, then evaluate the fuel hose going from the motors fuel connector to the fuel pump. With today's ethanol enriched gasoline, the original motors fuel lines and fuel pumps are degraded and breakdown with cracks and pin holes.

Another thought, if you have in line fuel filter between the tank and the motors fuel connector, then check it for blockage or trash. May have change it out. Some boaters, might even have placed a filter between the motor's fuel connector and the fuel pump. I am not familiar with Mercury's fuel pump...I am Johnny Rude guy, but if there is a filter screen in the fuel pump that may need to be cleaned or changed.

Try the no cost stuff first and always check to make sure the vent on the tank is open. It is hard for a fuel pump to pull gas from a tank that isn't vented.

Just a couple of things to think about or look into before dropping some cash for a new fuel pump.

Good luck!
 
thanks for the reply!

I have 2 plastic tanks, 3 and 6 gal, one new and one older, both have new hoses,bulbs and connector ends, and the motor acts the same way on either tank. Merc has an inline verticle small cannister style filter, and it had nothing in it after todays problems.

Ya it is 1o years old, the under hood hoses look fine, but i should probably change them out anyhow. I bought new Atwood connectors this spring, and notice they have to be pushed in really hard to get the spring keeper to lock on the tapered pin.

I've always had OMC motors in the past, now I have the 15 and a little 3.3hp Merc for a kicker on this boat, so I'm getting used to Merc's , where as I've always shied away from them before

There's a fuel pump rebuild kit I found online for $16, Probably should spring for one.

Just seems odd that shutting down for 5 min or so causes no problems, but 15 min or more does, but it starts and idles down nice, with only a half hearted pull on the cord.

Going out in salt water tomorrow, will surely bring the kicker!
 
I believe you have what is commonly called "Heat Soak" as your scenario fits the issue perfectly. Am betting you are up North a ways where you may still have a Winter blend fuel in your gas tank and trying to run it in warm to hot weather. Alcohol extended fuels will exhibit this also in warmer weather. Winter blend fuels will do it in a heartbeat.
Couple things are happening here. First, when you shut your engine off the cooling water drains out of the block allowing the block, intake and carburetor to heat up to a common temperature. Also, you have no airflow going through the intake vents and carb venturi to keep the fuel cool under the hood so it gets as hot as the engine is getting.
Alcohol extended fuels have a lower boiling point than fuels with no alcohol. There are also aeromatics added to these fuels and for Winter blend fuels the aeromatics are brought to a very high level.
Now, when you start your engine you are pulling a vacuum across different circuits in a carburetor. If you remember from Science class liquids boil at a lower temperature in a vacuum than at ambient pressure. What is happening is that as you accelerate you are switching from an idle circuit to a mid-range or high speed circuit and are pulling a vacuum across the mid-range or high speed circuits and are pulling hot fuel vapors and air up that circuit instead of cooler liquid fuel and air bubbles. Engines will not accelerate on vapor.
When you push in the primer you are pushing the necessary fuel behind the carb needed to accelerate.
After you run a minute or two the enigine and fuel cools to normal and will restart normally if only shut off for a minimal length of time.
Try buying fresh fuel or even better, non alcohol fuel and those symptoms will probably go away or be minimized.
Your primer bulb is not supposed to be hard while the engine is running. Remember, your fuel pump is sucking fuel from the tank and fuel line so the primer bulb is no longer pressurized while running.
 
hey Pappy

Ya, I'm In NH, we might be still running on winter blends. Fuel is fresh this week, added stabil and startron, as i used to do on my OMC's

I ran it after stopped for 15 min on idle for 1 min (before goosing it)and would run at idle trolling speed fine.

One pull on the manual prime button is all it takes, to take off normally.

And to think, burning "corn" instead of having it in out food chain, has caused all these small engine headaches!

I haven't been boating since 1996, till this year. Did we have alcohol back then???

I'm getting old, can't remember haha

I'll rebuild the fuel pump, but it that doesn't change anything, guess I'l have to live with it?
 
Just save the kit for the fuel pump until you need it. Why use it on a pump that is able to supply fuel to the engine at WOT and therefore functioning normally? Unless you source fuel without ethanol in it you are likely to have issues from time to time. There's no guarantee that I am 100% right but I have seen this scenario sometimes on a daily basis with customers. Changing fuel would be the easiest thing you can do to eliminate the engine as a source of your issues. You can try https://www.pure_gas.org and see if there is a station near you that supplies ethanol free fuel.
 
Ok took the grand kids fishing this AM, and had similar and worse problems!

Ran fine for an hour or 2, then lost power running almost WOT for 3o min. starved for fuel, had to pump bulb again to force fuel into motor. I could see the verticle fuel filter under the hood (clear plastic was almost empty). Got it running, but kept die-ing out. One Merc fuel connector had a mangled O ring under the ball, and leaked each time i pumped, the other tanks hose end gas fitting was in tough shape too. i bought these new last month--- Attwood, walmart-- niether would keep the engine running well.

So I fired up the 3.3 and cut the trip short

Came home and pulled the engine barb fitting off, and tried putting either gas hose fitting ( I took them off the hoses) and could just barely blow thru them

I had another new hose fitting in house, new, and putting that on the removed engine barb, I could bloww thru it with ease.

If I had that 3rd new fitting on board, I could have made it home ok

So no more atwood fittings for me, going to get an OEM Merc fitting for the tanks.

Looking at one of the hose ends, it almost seems like the rubber O ring was trying to come out of the fitting-- like it was now bulging outwards

hope this solves my problems
 
Will do

I'll be picking up new OEM connectors tomorrow

also pulled the carb , found the bowl spotless and to satisfy my curiosity I took apart the fuel pump to check for any sign of a pinhole or something amiss---- no problem there either.
 
Well one tank is a 3gal plastic with no quick connect on the tank end and a sierra bulb, new gray hose, the other is a older but clean OMC plastic tank with an OMC fitting at the tank end, new grey hose, and atwood bulb.

the plan is to get Merc bulbs for both and OEM fittings for each,

Funny thing is I removed the O rings from the distorted Atwoods, and they are swelled looking, and "D" shaped in cross section, not round like a normal O ring would be , if you were to cut it anl look at the cut ends.

Any OMC O ring I ever replaced was round in cross section.

BTW, this is my first Merc-lol

I was happy for the 3.3hp little kicker I just traded my older 6hp Evvy for, got me to the ramp even it was a SS on a 20" transom
 
So the problem is solved!!!

I went out today with new OEM Merc connectors on both tanks, and new bulbs (OEM OMC, they didn't carry the Merc brand)

At no time did it falter upon acceleration, and the see thru Merc under hood fuel filter was always full. Stopping for 15 min or more made no difference either.

It ran no different from before in terms of idleing and starting, when it was running with no problems before, so changing the fuel pump diaphragm made no difference.

I will say that the Merc carb was easy to remove and install, no finger contortions to try to get the bolts back on.

Thanks for the replies and suggestions, this is a great forum!

So after replacing the plywood seat tops, replacing the transom and raising it to 20", the 30 y/o tinny is ready for striper and flounder fishing tomorrow!

She ain't pretty, but she's functional!
 

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