40HP Mercury outboard question/problem

[SpeckWick]

I have a 40 HP Merc 2 Cyl. outboard with oil injection. I have been having trouble keeping it running at idle. As it runs at idle speed, the priming bulb goes soft as well, but I'm not sure wheteher that is actually normal or not. Also, if I run across the lake, turn it off for a while to fish, when I go to start it again, I have to put the throttle in neutral and give it a lot of gas. I tried adjusting the idle up, whih seems to keep it running at idle speed a little better, but at 1000-1200 rpm. Is this something anyone else has run into or does anyone have an idea of what I can do to fix the problem? The motor will run, and I can use it as is, but I fear continuing to do so will only make it worse. Help??!!

[Barnacle Bill]

That could be any one of a number of things. Bas gas? Check your fuel lines and especially primer bulb. All should be soft and pliable with no cracks. Be sure tank vent is open and clear. If all those are good you could have pin holes in the fuel pump diaphram. They are easy and inexpensive to rebuild. Next would be trash in the low speed areas of the carb. Its normal for the primer bulb to get soft (but not collapse) while the motor is running as there is fuel flowing thru it.

[papasage]

try this site . doc is a merc.tec.

http://www.themarinedoctor.com/cgi-bin/YaBB.pl

[bigfishn]

I had the same type of problem with a 50 hp merc.
We switched out the bulb and it was better for a while.

[shawn-n-the-buckeye]

IT not a johnson that whats up

[hunt4crappie]

I had the same problem. Put on a new primer bulb and no more problem. The mechanic said the valve in the bulb was bad.

[SpeckWick]

Thanks for the tips. I actually idled it up just a little to make it through a tournament Sunday, and it ran a lot better, but still not 100% right. Also, it seemed to hurt my top end RPMs, which with a 40HP I haven't much to give up to begin with. The primer bulb seems to keep coming up, so I'll start there. Question, though. If there were cracks or holes in the bulb or line, wouldn't it be tough to get pumped up to start with?

[Cane Pole]

Not the best chart but all I got.

[freeflow_23]

Sounds like a fuel pressure issue to me.
Bad gas could also be a factor.

I have the same exact motor and mine runs a little rough when cold at the ramp. I have to keep the idle speed up for a minute or two and then everything runs normal.
My bulb requires pumping after sitting for several hours. If I don't pump it before starting my motor, it is likely to cut off after starting. I think the motor needs that initial fuel pressure built up when starting at idle speed.

Seems Little or No Pressure = Rough Idle

I've also been using Stabil in my gas to help keep my gas fresh and provide quick starts. I never have to turn my key twice.

[shipahoy41]

I had that happen to me on Mogadore Reservoir when I was living in Akron. My boat was towed to shore and taken to the marina. They drained the gas tank and also replaced the bulb. They also told me to put "Stabil" in it at least twice a year.

old ship