75HP Force/Mercury 2-Stroke Stalls at Odd Times

[pshelfo]

I have a 1999 75Hp Mercury/Force 3cyclinder outboard 2-stroke which is having a few stalling issues. Boat cranks up and runs fine off the dock. After fishing for awhile, I crank the motor and then when I put it into gear its lagging, has trouble taking throttle and dies out. I then have to crank and rev it up in neutral and then when I put into gear it may lag a little but then I get up on plane and all is good until I get to the end of the day. When I come off plane and idle to the dock, once I put in reverse right before stopping it dies out. Not fun as I can't stop the boat from hitting the dock harder than I want. I am not sure if this could be a fuel or carburetor issue.

I have been seeing a slight fuel stain coming down the outside of the motor but can't find a leak inside. Thought maybe this was from the cards when you tilt the motor around.

Curious if anyone else had this weird issue.

 

[roscoe]

If you haven't replaced the fuel pump diaphram in the last 5 years, start there. $25 for the kit. They don't last forever.

So the motor acts like it is flooded, then clears out and runs good ?

That will happen if the diaphram is worn or torn. It will leak fuel into the crankcase. Not surprising on a 23 year old motor.

As for stalling when moving into reverse, it could be idle is a little low, or carb(s) need a cleaning.

 

[pshelfo]

So the motor acts like it is flooded, then clears out and runs good? Yes this what it appears. Good point about the fuel pump as I did not even think about that. Should I replace the entire pump or is the diaphram easy?

 

[roscoe]

Just a rebuild kit from Mercury. OOPs, price is now $31.
A couple of gaskets, diaphragms, check valve.
Remove fuel line, remove screws, replace internals, put it back together.

Mercury-Mercruiser 21-857005A1 DIAPHRAGM KIT​

Mercury used to send an instruction sheet with the parts, with any luck, they still do.

 

[Texasmark]

I had a black speck of deteriorated fuel line floating around in the bowl of one of my carbs on my 90 Merc. causing a similar problem on a 10 year old engine running E10. Final solution to the problem was new fuel components in the engine including filter, lines, pump kit and carbs redone and since I also had brown chips in the fuel filter I cut open a new tank to engine line and bulb.