New Question for Fishinwrench or anyone with a 2006(?) Mercury 20 horse 4 stroke with carb

[yowoodchuck]

So my lake buddy here at Sugar Creek Lake (BTW-fishing sucks here and its not very pretty), has a pontoon boat on a lift that overwinters on the lift.

The last time I got him to pull the boat out this spring, we put in new plugs, waterpump, and lower unit oil, along with new filters and oil. All worked great. About the middle of July, the motor started leaking a little gas...It is really hard to see where this gas is coming from, as I'm hangin off the back of the pontoon and trying to survey the conector, filter and carb.  It seems not to be coming from the connector on the motor or the incoming fuel line connector.  To make matters worse (think about what you wish for), his new wife now considers the boat Hers and wants it to be available to fish all the time she is there. She also wants to go anytime he goes, so she can outfish him.  So, I'm looking for what the problem (other than his wife) might likely be, so that when we do pull the boat out I have any likely needed parts in advance...should I get a new carb?  New fuel pump? Some gaskets?   It has to be fast and easy...Anyone out there dealt with this?

Many Thanks, any and all ideas appreciated.

[aarchdale@coresleep.com]

I would start with a new fuel line from tank all the way to carb

[yowoodchuck]

Thanks for the tip,  Beats changing the carb...I will make sure I have new fuel line at the ready.  It is really hard to see anything--while it is on the water...but it really seems to be inside the cowling 

I'm sure when it is on dry land it will be much easier to figure where things are happening.  Gas leaks make me nervous, when I smell gasoline on a boat--I think fire will ensue sooner or later.  🔥

[fishinwrench]

4 hours ago, yowoodchuck said:

should I get a new carb? 

Ha!   You forget what (who) you're dealing with.   

 

Of course it's NLA......but even when it wasn't Mercury's price was about 600.00 🙄

 

[fishinwrench]

2 hours ago, yowoodchuck said:

Gas leaks make me nervous

Smart guy !   👍

[yowoodchuck]

how about a Tohatsu labeled carb?  They built this for Merc, didn't they?

I remember when he bought the boat...the dealer offered the 20 hp merc that was a year old and still in the crate for $ 1800

Of course, as delivered it had to be reproped to push the 20 ft pontoon...what a deal!

I urged at the time that the extra thousand or so to get to a Yamaha was worth it...so it goes.

[fishinwrench]

1 hour ago, yowoodchuck said:

how about a Tohatsu labeled carb?  They built this for Merc, didn't they?

What you're dealing with is a Mercury labeled Tohatsu.    They didn't just build the carb...... 

It is a Tohatsu powerhead and fuel system, with a Mercury designed lower unit and ignition system......which is kinda silly to me because I challenge you to find a single Tohatsu with an ignition system failure.  Mercury's with ignition system failures are a daily occurrence at any outboard shop.

[MrGiggles]

Mercury was in bed with Yamaha up until 2006 if I'm remembering right, it may very well be a Yamaha powerhead.

My first thought, you presumably changed the fuel filter, it started leaking fuel soon after. Start looking at everything you touched.

About all there is on that motor is an impulse driven fuel pump (could leak through the diaphragm out of the weep hole), two fuel lines, the carb, and a filter. There's not a lot to rule out.

It appears that there are two vent hoses that attach to the carb and tee together, if there is fuel in that hose, there is likely some debris in the needle and seat that's causing it to overflow. It probably runs through and out of the lower cowl so it cannot fill with gas.

The primer bulb is an excellent tool for creating pressure in the system without the engine running, and will help you find a leak. If you are squeezing the bulb and it is not holding pressure, that is a sign that there is a leak somewhere. It should firm up and stay that way for quite a while, if the engine is off.

This scenario likely would have been an issue from the get go, but I have heard that some of these new sealed fuel tanks can create enough pressure in hot weather to pop off the needle and push gas through the carb overflow. I don't think it's very likely, but if you've checked everything else over and can't find anything, something to consider.

 

[fishinwrench]

36 minutes ago, MrGiggles said:

Mercury was in bed with Yamaha up until 2006 if I'm remembering right, it may very well be a Yamaha powerhead

A Yamaha would have a Mikuni carb.   

[fishinwrench]

38 minutes ago, MrGiggles said:

I have heard that some of these new sealed fuel tanks can create enough pressure in hot weather to pop off the needle and push gas through the carb overflow

You heard correct.