At My Wit's End with My 2001 Mercury 5hp Two-Stoke Outboard !

[Janae]

It's in great condition - other than the fact that I can't get the damned thing to run right.

We have continuous problems with flooding. We've recently replaced the filter, and the float needle.

We use high quality gas (ethanol free), 50:1 synthetic marine 2 cycle oil mixture as well.

We've taken the carburetor apart half a dozen times now. Thoroughly cleaned it out each time. Replaced the gas inside. Made sure there were no holes in anything, no leaks, no blockages, etc. It looks like it should be running like a dream.

However, it's always flooding. The float valve and needle appear to be working fine, in the right position, not sticking.

It's a 50/50 that can get it to start. If we don't flood it on start, we have to manually regulate the external fuel valve on the outside of the cowling to prevent it from flooding while it's running. This means, every 30 seconds or so, opening the valve for a second to allow some fuel to come in.

I'm not sure where to go from here. Rebuild kit? In my mind, flooding would suggest issues with needle/float valve - but we just replaced those. They APPEAR to be in the right position, not sticking, etc.

Does anyone have any words of wisdom?

[perchance]

Check your float level for starters and make sure there isn't a hole in the float allowing fuel in.

[MarkJ]

What sort of fuel tank is it?

Plastic?

Does it bulge out in the heat of the day?

Damn thing does that to mine and floods the OB.

So I disconnect the fuel hose unless its running, start without it on, and undo the air vent.

Don't know if this will help

[Janae]

Originally Posted by perchance

Check your float level for starters and make sure there isn't a hole in the float allowing fuel in.

No hole in the float. When the carb is apart, it sits level.

[Janae]

Originally Posted by MarkJ

What sort of fuel tank is it?

Plastic?

Does it bulge out in the heat of the day?

Damn thing does that to mine and floods the OB.

So I disconnect the fuel hose unless its running, start without it on, and undo the air vent.

Don't know if this will help

I should have specified that it's an internal fuel tank. Also, I should mention that we've also checked the fuel lines and tank for contaminants.

Thanks for the suggestion though!

[donradcliffe]

There is still something wrong with your float valve. Take carb off, drain, attach a hose to the fuel inlet and blow air in while inverting the carb. The air flow should cut off completely and dependably when its upside down.

If the internal tank vent is blocked and it is pressurizing in the sun, try leaving the fill cap loose.

[brutb]

Does your motor have a diagphram fuel pump, if so check it.

[motion30]

yes fuel pump would be where i would start

[s/v Jedi]

Originally Posted by motion30

yes fuel pump would be where i would start

Internal tank? I think they are gravity feeding...

The only weirdness I know of with Merc 2-strokes is that the 2-cyl 8-15hp have this coil for ignition that can drive you mad when it's defect because the motor runs fine in tank tests... only under load it starts to suffer.

ciao!
Nick.

[Blue Stocking]

Originally Posted by s/v Jedi

Internal tank? I think they are gravity feeding...

The only weirdness I know of with Merc 2-strokes is that the 2-cyl 8-15hp have this coil for ignition that can drive you mad when it's defect because the motor runs fine in tank tests... only under load it starts to suffer.

ciao!
Nick.

Have the same problem (coil) with my 2005 1.5kw yamaha.
It was designed in Outer Mongolia, by French Foriegn Legionaires, to be used as a helicopter motor on the west face of the Andes--or some sh*t like that when I talk to the techs.

[s/v Jedi]

Originally Posted by Blue Stocking

Have the same problem (coil) with my 2005 1.5kw yamaha.
It was designed in Outer Mongolia, by French Foriegn Legionaires, to be used as a helicopter motor on the west face of the Andes--or some sh*t like that when I talk to the techs.

Yes, I posted that because it is sometimes so misdiagnosed. But I don't know which outboards have that coil and which don't...

ciao!
Nick.

[cabo_sailor]

It's not an outboard motor but I have a gas pressure washer that was doing the same thing. I finally determined that even though the float was up, the attached needle valve was letting copious quantities of fuel past, even in the shutoff position. After messing with it for an afternoon I found a whole new carb was only about $30. That's the route I took.

So perhaps a close look at the needle valve controlled by the float is in order. A small piece of grit or sand could be preventing it from sealing when the float is up and in the closed position.

Rich

[motion30]

If that merc is made by tohatsu which think it is, there is a fuel pump on the carb There is a carb rebuild kit which includes the fuelpump parts

[tsenator]

OMG !! I've had the same problem the last few years with my 5HP Merc ! (I think its a 2001 also!!)

I had it flood so bad I just used to remove the hose connection from the external tank every 30 seconds and then reconnect when it seems the fuel bowl was out of gas.....

It seems the float in the bowl wasn't doing its job. No problem starting the engine but after a few minutes it would stall and not start again unless I drained the carb fuel bowl.....and then the cycle would happen again. I have tried the same exact things as you (replace the float needle, etc) and checked all the jets, etc and couldn't fix the problem (never replaced the whole carb yet).

But then I found a solution. I drained and dried out ALL of the engine, the external and the internal tank BONE DRY. Then I went to to the closest gas station and got the freshest gas I could and tried it again. It worked fine and I did not have ANY problems the rest of the year just as long as the fuel was 100% fresh with NO TRACES OF WATER .

What I think has been happening the last few years is that all the gas has ethanol in it around hear and it just absorbs moisture (even though if you look at the gas it might look fine) So even if the gas is even a few months old it absorbs moisture and the float in the carb just does not do its job -- and I mean ANY MOISTURE in the gas (forget if its been sitting around all winter - even in a closed container).

Get ALL THE WATER OR MOISTURE OUT OF THE SYSTEM (even if you cant see it) -- Try what I said and tell me if it works for you. It did for me.

Tom

[Marutji]

Originally Posted by Janae

No hole in the float. When the carb is apart, it sits level.

Hey Buddy, I feel your pain. I don`t know if you have solved the problem, but I just solved the exact same problem on mine after banging my head against the wall for weeks. I took a 1000 grit piece if wet and dry and took the smallest amount off the sides of float pin. The problem is, that when you test the float by hand all seems good right? Then you put the whole thing back together and set off and all is well right? Then comes the flooding again arrgh! The problem is that the test you make by hand of the float exerts much more force on the float than the petrol rising actually does, so in a way, the test is invalid. The tiniest bit of friction on the pin will stop it closing properly. Ever so slightly smoothing the pin with 1000 grit (and then rinsing with petrol) now has my Mariner purring again with no flooding. Good luck with yours!