1998 Mercury 15 hp, 4 stroke, ELH---throttle setting for cold start

[AnthonySci]

Four months ago I bought this 1998 electric start Mercury outboard with tiller from a Seattle mechanic---the motor was already warm and running when I arrived. He said he'd rebuilt the carb, changed the oil & filter. The motor ran normal. Before I left, he disconnected the gas line and ran the motor out of gas.

Now very difficult to start and when I am able to get it to fire, it runs at most for 15 - 20 seconds, then it dies. I've been setting about 1/4 throttle. Full choke, 1/2 choke, no choke doesn't seem to change the rare occasions it does start.

I've got NEW non-ethanol gas, new plugs. Primer bulb stays hard.
Today, I pulled the carb apart: gas was in the bowl. Main jet, pilot jet, the needle valve---all were clean. When I manually pushed down on the diaphragm plunger--it squirts gas.

Where should I set the throttle for cold starting?
Serial no. 0G 697 665

I appreciate any help

 

[AnthonySci]

Does anyone have a MERCURY OWNER'S MANUAL for a Merc, smaller hp, CARB, with electric start, and tiller for throttle control?
Post a "sticky" of the starting procedure page from the manual?

 

[flyingscott]

There should be a stop to prevent the throttle from overreving in neutral. When you start the motor turn turn the throttle as far as it will go.

 

[sutor623]

the motor was already warm and running when I arrived.

I HATE THIS!!! One of the most dishonest things you can do as a seller in my opinion.

Anyways not trying to be negative, but man this irritates me so much. And from a mechanic, by the way.

I wouldn't even mess with that dang motor, and just take it back where it came from and tell him to fix it. It sounds like you have tried everything to get this thing started.

How long was it setting since you bought it?

 

[AnthonySci]

The mechanic's no help---he's 150 miles north of here; via phone text, he told me to buzz off--it was running at his house!
Update, after reinstalling the carb., the only way to start is starting fluid. I verified gas gets to the carb inlet.
So I pulled the carb off, there was only a 1/4" of gas in the bottom of the bowl.
Is my next move to purchase a new (oem) diaphragm for $20 ?

 

[AnthonySci]

One more question: I'm guessing the mechanic was running ethanol gas, does it make sense to buy "dip" for the carb body, esp. all the extremely tiny openings visible when I remove the flat chrome cover located on the TOP of this carb?

 

[ondarvr]

Squeezing the primer bulb will keep it running if the fuel pump was the issue, and the squeeze bulb should not stay hard once the motor is running.

​Could be an air leak.

Is the vent on the fuel tank open?

There's a couple of things with these motors, they are set up very lean from the factory and hard starting when cold can be normal, also they frequently like the throttle setting very low, or even at the lowest idle setting when starting cold.

​There should be a low speed adjustment screw on the carb, it may be covered by a brass plug, if you remove the plug you can adjust it for much easier starting and idling. ​Every motor is a little different in exactly how it like's to start.

 

[ondarvr]

The fuel you run is irrelevant.

 

[AnthonySci]

Thanks for the additional info.
Now that I see this 4 stroke Mercury has a separate fuel pump before reaching the carb body.
My question: what's the function of the spring loaded diaphragm located inside, at the bottom of the carb. bowl ?
When there was 1/4" of gas in the bottom of the bowl, when I depressed the vertical plunger, visually I observed it squirt gas into the bowl.

 

[ondarvr]

It's an accelerator pump, 4 strokes like a squirt of fuel when you turn the up throttle quickly.

 

[AnthonySci]

I took the fuel hose off of the carb inlet and purged the entire fuel line from gas can to carb just in case water had condensed from mid-November until now.
Next, I took the bowl off the carb and filled it with gas about 3/4 full, then I carefully attached it back onto the carb body without turning it over.
After re-installing the carb, I adjusted the set screw on the throttle linkage above the stem of the accelerator pump, (it had been as far up as it could go; never making contact with the top of the accelerator pump plunger even at full throttle) I adjusted the set screw down so that the linkage contacted the top of the pump, just beyond the neutral setting on the throttle.
Full choke, throttle at neutral, the motor started within 2 seconds and purred like a cat! BUT, after a few minutes letting it warm up, when advancing the throttle, oily "soot" began coming out the exhaust, contaminating my water barrel; I throttled back to idle---continued running smoothly.Probably had it running 15 minutes and the entire time it was "peeing water." I shut it down though because I was concerned about the black soot oil slick that gathered on the top of my water barrel. I pulled the plugs and they were coated with black soot. I assume the black soot indicates it's running way too rich. ?

So, I adjusted the set screw for the accelerator pump back to where it was originally (all the way up.) I put new water in my barrel, and replaced the plugs with the back ups I had. Again, it started immediately. I let it run maybe 3 or 4 minutes. I shut it down. I pulled the plugs and they were both already beginning to "soot up."

Perhaps, it's time I take this motor to a mechanic in Portland?
Or?

 

[AnthonySci]

I'm closing this thread.
My solution for cold starting a 1998 Mercury 15 hp, 4 stroke:
Set throttle on tiller handle at "neutral", full choke , with an electric start, it will fire up and run at in 2 to 3 seconds. (The air temp, was about 55 degrees F.)
If then the motor won't fire and run---and you have fresh gas. Next, purge the fuel hose system by removing the fuel line where it enters the carb and squeezing the primer bulb repeatedly, discarding enough gas to purge any that had remained behind in the fuel lines from last season.

Thanks to all those who responded to this thread. I learned much.

 

[sutor623]

How long was it setting since you bought it?

In that case it seems that this would have been a vital question for you to have answered a few days back. Anyways, glad you have it figured out. Either winterize your motor or run it through the off-season. Use fuel additives regularly. This will solve/prevent 90% of all issues.