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Help...just about going crazy: 6hp 2008 Mercury 4stroke

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bigtime_mcalpine

Regular Contributor
Sorry, newbie here with no contributions to make yet...unless you need help with your Volvo cars, those I can handle!
My 4 stroke is driving me up the wall. Bought out sailboat at the beginning of the season. Got it for a steal partly because the party selling believed the motor to need servicing.

I took a look at the motor and saw that the fuel connector bit was missing (the piece that connects to tank line. Purchased that, put it on and away she went. Purred like a cat. Fast forward 6 weeks. Out for a sail and motoring back when motor just cuts out. I pull the cord, it starts, then stalls. This is repeated a few times. We end up getting towed in. Next morning, starts like a champ so I took it around the harbour making sure that it could run and restart without issue. No problems.

Next morning same thing. No issues.

Next sail, I pull start it, it struggles then dies. No life since then.

I have:
  • checked fuel lines (disconnected each and blew air through)
  • Removed and inspected fuel pump. Looked fine, metal bit had good spring to it and retracted with moderate force
  • Checked the carb, took it apart, cleaned it, inspected/cleaned needle valve (looked perfect)
  • Checked for spark - it has spark (enough to give me a bit of a tickle anyway) - going to get a spark tester to be sure
  • inspected fuel filter and pick-up in tank. Clean.
  • Inspected sparkplug. Looks darker than it should be but not so much that it would prevent a start I'm thinking
  • Inspected kill switch and unplugged it from coil pack for kicks, no change.
  • Inspected flame ignitor, clear clean obstruction free.

I'm at a loss. Haven't checked for compression but before it went, it was purring so not sure that's a factor. Will be checking anyway. Just need to grab a tester.

Any ideas? This is a simple enough motor and not that old, why the heck won't it start???

BTW - it did sit most of last year so lots of spider webs that I had to clean out. Wondered about verifying exhaust but not yet familiar with routing.
 
If you can come up with some sort of a squirt bottle give the carbs a little splash of fuel/oil mix and see if it will light off. If it does then we can try to figure out where your fuel system is holding up the parade or know to look elsewhere.
 
Swagonmaster said:
If you can come up with some sort of a squirt bottle give the carbs a little splash of fuel/oil mix and see if it will light off. If it does then we can try to figure out where your fuel system is holding up the parade or know to look elsewhere.
Click to expand...

Thank you - squirt in via the air intake mesh? As a lazy alternative, could I squirt a small amount of carb cleaner or other into air intake as I'm pulling to see if that makes a difference.
 
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bigtime_mcalpine said:
Update: compression test ran fine 110psi
Click to expand...

Update - let it sit all day. Cranked it this afternoon and it came to life for all of 3s then died. No throttle response. This was with choke on. Tried to start again, no dice.

Here's the challenge: $10 says if I let it sit for a couple of days the problem will not appear and I'll have a devil of a time troubleshooting until I'm back on the water and need it most.
 
Swagonmaster said:
Yes It won't take much to see it run better or no change.
Click to expand...

That was a good idea. I sprayed some MAF cleaner in there and it came to life. Then I cranked it a couple of time again. Nothing. Sprayed more MAF (not much) and it came to life again. So looks like fuel is not getting to the cylinder.

In that respect i have:
1) removed each hose (and fuel filter) leading to carb and blow through to make sure all are clear
2) uncrewed carb bowl drain to make sure fuel is getting there (it is)
3) Blown in the fuel pump and made sure I could not blow in the other way, no issues
4) inspected the fuel lines to tank for leaks, none found.

Related question: if primer bulb or other part (other than carb itself) was faulty, shouldnt the engine at least start if carb bowl is full of fuel? Just trying to narrow this back down to something related to carb.
 
Ok, I am taking for granted that the liquid in the carb is not water here, if there is fuel in the carb and not in the engine then the carb passages must be stopped up with trash of some sort.
 
Swagonmaster said:
Ok, I am taking for granted that the liquid in the carb is not water here, if there is fuel in the carb and not in the engine then the carb passages must be stopped up with trash of some sort.
Click to expand...

Definitely fuel. that was my first thought too (carb must be plugged). I have taken carb off again. I took bowl off, spotless. Pulled the needle valve out, spotless, inspected passages, spotless. It is a super simple carb so not that much to inspect.

I have some concerns with primer bulb though. Not sure it’s getting as hard as it needs to be. Could that prevent a start even though fuel makes its way to the bowl of carb?
 
The primer bulb is a manual fuel pump.-----It fills the carburetor with fuel when operated.------After that it does nothing !-----The primer bulb saves you from having to pull the recoil 20 times to fill the carburetor using the pump on the motor.----I say that you need to clean the carburetor , very small holes in jets are often missed on the first attempt.
 
Since it is going to require some pressure to blow out the passages in the carb if you don't have access to an air compressor just use your can of throttle body cleaner with a straw nozzle.
 
Update:

Took carb apart a third time this morning. Turns out that there was one VERY IMPORTANT orifice that I did not inspect (not sure why). The tiny hole in the retaining screw for the main jet. That one was all but closed. Took a single strand of wire from a bike shifter cable and cleaned it out. Re-assembled the carb and re-installed.

Took a few pulls but it started. Then it ran for a good minute (that's progress) then it stalled.

I then tried to get the primer bulb to inflate but get this - it would not. And it was accompanied by the sound of air coming out the two top orifices on the carb. Guessing this is normal if you are pushing air through the system.

Engine would not re-start.

So I raised the gas tank such that it was above the level of the engine. Tried to pump gas using bulb, was a bit easier. Pulled and started the engine. Engine ran but started to slow down. So I gave the bulb a few squeezes, engine sped up, engine tried to stall, I squeezed bulb and engine ran faster. Effectively I was able to keep engine alive by giving it some extra gas every once in a while.

I guess I will start with replacing the bulb but I'm wondering if maybe the fuel pump is not doing its job. On the other hand, if air is entering the system, the fuel pump can't do it's thing I guess.

Next step, head back to dealer. Just need to decide whether I'm purchasing the entire hose assy or just a bulb.
 
shoot, I hope i didn't screw something up in the carb....

Went to dealer, got a new bulb.

Came home, tried to prime the bulb, no can do. Air keeps coming out the two vent tubes at the top of the carb (see pic below).

When i cleaned the carb, i put a very small wire into these two tubes. Did I bust a membrane in there??? F me.
vent tube 2.jpgvent tube 1.jpg
 
I will have to let someone that really knows comment but fittings of that sort usually have a hose on them and having two of them makes me think that they should be connected, try it and see what you get.
 
bigtime_mcalpine said:
shoot, I hope i didn't screw something up in the carb....

Went to dealer, got a new bulb.

Came home, tried to prime the bulb, no can do. Air keeps coming out the two vent tubes at the top of the carb (see pic below).

When i cleaned the carb, i put a very small wire into these two tubes. Did I bust a membrane in there??? F me.
View attachment 24658View attachment 24659
Click to expand...

Final Update: Success! Pierre "1," mercury outboard "0."

Re: above, turns out that when I inspected the tank, the pickup came off when I put i back together. This explains inability to inflate bulb solid (I needed new fuel lines and bulb anyway so no big deal).

In the end two things were biting me:
1) Gunked up retaining screw orifice for main jet in carburetor and
2) Small leaks in fuel hoses and crappy aftermarket bulb

@racerone and @swagonmaster - I really appreciate your comments. Without those, the motor would be in the shop right now. Thank you for helping a newbie out!

Next job: figure out how cost effective it would be to install an electric starter on this motor...
 
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