Bottom carb flooding

[Boatdrinks1965]

2005 Tohatsu MD40 3 cyl 3 carb. Bottom carb has fuel pump on it. When I pump the bulb gas came out of bowl gasket and throat of carb. Took fuel pump apart both diaphrams look ok so ordered bowl gasket and needle valve. Seat is not replacable and appears fine. Old needle valve appeared to be fine. Installed parts and bowl gasket doesn't leak but still comes out of the carb throat. I don't feel like I'm pumping the bulb too hard and the whole reason it was discovered was because the motor ran low on power and it appeared the bottom cyl was flooded. Short of ordering fuel pump diaphrams not sure what else it could be. I looked the existing ones over carefully. Thought I had ordered them just in case but apparently I didn't. Have not tried running yet because of rain but will try tomorrow. At a loss here. This is the one with the fuel pump mounted on it.

 

[GA_Boater]

Does this motor use hollow plastic floats? Your symptoms sound like either a float level adjustment or a soggy/gas filled float.

 

[Boatdrinks1965]

Plastic floats and appear to be in good shape. I need to add when the carb was off I lightly blew through it and it held pressure. I would think fuel pump but that would send fuel straight to the intake and as I said in earlier post the diaphrams look fine. Even used magnifying glass.

 

[wrvond]

Plastic floats can look fine but still sink. The only way I know to check is to remove them and try to float them in an open bowl of fuel.

 

[pvanv]

2005 Tohatsu MD40 3 cyl 3 carb. Bottom carb has fuel pump on it. When I pump the bulb gas came out of bowl gasket and throat of carb. Took fuel pump apart both diaphrams look ok so ordered bowl gasket and needle valve. Seat is not replacable and appears fine. Old needle valve appeared to be fine. Installed parts and bowl gasket doesn't leak but still comes out of the carb throat. I don't feel like I'm pumping the bulb too hard and the whole reason it was discovered was because the motor ran low on power and it appeared the bottom cyl was flooded. Short of ordering fuel pump diaphrams not sure what else it could be. I looked the existing ones over carefully. Thought I had ordered them just in case but apparently I didn't. Have not tried running yet because of rain but will try tomorrow. At a loss here. This is the one with the fuel pump mounted on it.

Ok, it is NOT an MD40, which is a TLDI. It is an M40D2, 3-cylinder 2-stroke. If in North America, doubtful it is a 2005 year of manufacture, as TLDI motors replaced the carbed-versions before then due to EPA regulations.

Fuel pump gasket set has nothing whatsoever to do with flooding.

Your needle is not seating properly. Period.

Did you remove the carb and completely disassemble it, then do a full 4-plus hour soak of all non-rubber parts in carb dip, followed by a liberal blow-out with generic carb spray... then a careful reassembly, noting float height? These floats are hollow white (yellow with age) pillows of air, so if one is not floating properly, it would likely have gas sloshing around inside it.

 

[Boatdrinks1965]

Paul you're right. It is the M40D2 but it is a 2005. I was looking at parts and must have gotten that stuck in my head for some reason. The float is white with no yellowing and no gas inside. I don't see how the fuel pump would have anything to do with it either but a marine mechanic told me to check it. I have a canister fuel filter and have always used fuel stabilizer and the carb was very clean inside. Given I felt it was a needle valve issue I have not soaked the carb and done a total clean out. Just got the parts yesterday after quite a wait so needless to say I was disappointed to still have a problem. Rain moved in on me before I could get a hose on it to run it which I will try tomorrow to rule out maybe that I'm pumping the bulb too hard. I rarely have to pump the bulb even when it sits for months and the whole float system seems frail compared to the old Evinrudes that I'm used to. I'm just trying to get a list of anything possible because the parts are cheaper than towing it 100 miles to the closest dealer. I'm not familiar enough with these carbs to do a total rebuild myself and with the cleanliness of the bowl I'm not convinced that is even necessary. I have a jet drive on it so it's a PITA to run on a hose but no rain tomorrow so that is the plan just to see if the fuel pump pressure causes the same problem with the new needle valve. The troubling part for me was the old needle valve seated fine with lightly blowing into it as does the new one. Maybe the float is faulty. Thanks

 

[wrvond]

As Paul said, fuel is coming out because the needle valve isn't closing. If the floats are floating, and the valve seats, then the floats are adjusted too high and too much fuel is entering the bowl before the valve seats. Isn't there a tang on the float hinge that fits through a wire loop on the bottom of the needle valve?

 

[Boatdrinks1965]

As Paul said, fuel is coming out because the needle valve isn't closing. If the floats are floating, and the valve seats, then the floats are adjusted too high and too much fuel is entering the bowl before the valve seats. Isn't there a tang on the float hinge that fits through a wire loop on the bottom of the needle valve?

No it's all plastic. I'm considering switching one out of one of the other carbs and see if it still does it cause I did buy extra bowl gaskets.

 

[wrvond]

I see. Switching them is the right thing to do at this point.

 

[Boatdrinks1965]

Ok so the water pump easy project ended with parts ordered for the jet drive. I am short a water pump gasket as well so since I've got to order parts from both places I'll replace the float while I'm at it and leave the other 2 carbs alone. Will update once I get at it again. Thanks for the help.

 

[Sea Rider]

Sometimes the needle although being in good pointy cond can stick inside needle valve, needle valve can collect unwanted 2 strokes oil gum like formation that contributes to this issue. Can clean internal valve seat to smooth & shinny condition wetting a thin cotton swab with tooth paste and turning swab in circles as to clean and polish internal valve.

Repeat till looks shinny. If out of standard swabs, make a swab using a wooden thoothpick or match by rolling tight some cotton on tip, needle won't stick back ever.

Happy Boating

 

[Boatdrinks1965]

Ok so bottom carb flooding required new float. Old float seemed fine as in dry and not too discolored for a 10 year old motor. Anyhow had a new problem pop up when I went to test it. Top carb was not getting enough fuel. Long story short 1 year old Tempo fuel hose was coming apart inside and not pumping up the carb. Strange that the fuel pump couldn't overcome it but that was the deal. Runs like a champ now. Thanks and fellow Tohatsu owners those floats are tricky. Never had those problems with other brands but I can't complain cause this motor has a ton of hrs on it without any major issues.