I have a strange issue with my Johnson 150 (year 2000). I bought the boat last year about this time and put almost a full tank of gas in the boat. It started fine, and would run fine while traveling to my fishing location (about 10 miles). When I would shut off the engine, it would start, but cough, sputter, and stall if I did not get it in gear almost right away (get the RPMs up). After several tanks of gas, it was doing the same thing. At the end of the season, I drained all of the gas, and put fresh gas in the boat this year. It had the same behavior.
I took it to a local authorized dealer and he could not find anything wrong with the motor. He changed the spark plugs, and added a fuel/water filter. He could not reproduce the behavior. I had it out today for the first time since it was in the shop and it is still doing the same thing, maybe a little worse.
Once I get it over about 1000 RPMs is runs fine, but sometimes starts to sputter and stall when I reduce the RPMs under 1000. Often it won?t stay running long enough to get the RPMs up to where it won?t stall.
It always starts right up when it has not been running for 3 or 4 hours, and runs just fine in the driveway at home. After 10 minutes of running it in the driveway, I shut it down, wait 30 minutes and it starts right up and still runs fine. I cannot get it to act up at home no matter what I do.
I spun the fuel/water filter off and dumped it into a large glass. There is no visible at all in the fuel. At this point, I?m thinking that the fuel is not the issue.
Does anybody have any idea what I can try next?
Could a faulty fuel pump cause this? Some of the research I?ve done indicate that a bad fuel ?bladder? (whatever that is) may cause this to happen all of the time.
Could this be an electrical issue? Maybe the coil going bad?
Any help anyone could offer would be greatly appreciated. I?m at the point that I?m afraid to take the boat out on the water

Thanks, Dave
I took it to a local authorized dealer and he could not find anything wrong with the motor. He changed the spark plugs, and added a fuel/water filter. He could not reproduce the behavior. I had it out today for the first time since it was in the shop and it is still doing the same thing, maybe a little worse.
Once I get it over about 1000 RPMs is runs fine, but sometimes starts to sputter and stall when I reduce the RPMs under 1000. Often it won?t stay running long enough to get the RPMs up to where it won?t stall.
It always starts right up when it has not been running for 3 or 4 hours, and runs just fine in the driveway at home. After 10 minutes of running it in the driveway, I shut it down, wait 30 minutes and it starts right up and still runs fine. I cannot get it to act up at home no matter what I do.
I spun the fuel/water filter off and dumped it into a large glass. There is no visible at all in the fuel. At this point, I?m thinking that the fuel is not the issue.
Does anybody have any idea what I can try next?
Could a faulty fuel pump cause this? Some of the research I?ve done indicate that a bad fuel ?bladder? (whatever that is) may cause this to happen all of the time.
Could this be an electrical issue? Maybe the coil going bad?
Any help anyone could offer would be greatly appreciated. I?m at the point that I?m afraid to take the boat out on the water
Thanks, Dave