'97 Mercury 150 EFI Only Starts at full throttle

[rebelroy11]

Took the boat out a week ago and it started and ran fine all day until time to leave and would not start or stay running if it did. It would just idle a few seconds and sputter and die. Started trolling back to the ramp (pretty far) and would stop every once and a while to try again. Finally after trolling about 45 min or so I got it started, got it in gear and took off. I made it back to the ramp and killed it. Started it back up. Killed it. Started it back up. When I got home I hooked the hose to it and could not get it to start. The next day it fired right up but would only idle about a minute and die. Then struggle to start again. Pretty much did the same thing for the next 3 evenings after work. I use Mercury fuel treatment but decided to add some seafoam and change the plugs. Seemed to run a bit better after that. It would idle and stay running and sounded a bit better. A few days later I went back to the lake to pre-fish a tournament and the same thing. Started and ran fine all day and right when it was time to leave it wouldnt turnover and if it did it would sputter and die. So AGAIN started trolling back. My fishing partner kept trying to get it started while I was trolling. He finally got it started by holding the hot foot to the floor and even then it wouldn't idle, just had to back off the throttle and throw it in gear and go. Once the boat was on the trailer and still in the water I killed it and it started and idled. Killed it and tried again and wouldnt start. Instead of trying the full throttle thing again I just signaled him to pull it out and head home.

A few things I've noticed that may be normal but one of those things you notice when you're looking for something is A. With the key on the fuel pump runs and continues to run. I assumed it would only run or prime for a few seconds but it keeps going and going. Normal? B. I noticed this last time out that the primer bulb will not get tight. Since I've had it never got really tight. I just pumped a few times usually and it would start up with no issues. But now I noticed I can squeeze all day and doesnt really tighten or fill up. There is no inline filter between the bulb and connector to the motor. Bulb couldve always been like that but I don't really know. The fuel pump was replaced 4 years ago and the trigger replaced 2 years ago. Other than that I've had no issues. My best guess is that is sounds like a fuel or fuel delivery issue. I am getting fired on all cylinders.

Any ideas on what to check and/or look for or test?

 

[Chuckberg2]

check your tank for anti-siphon valve, possibly giving you fits

 

[rebelroy11]

check your tank for anti-siphon valve, possibly giving you fits

Yeah there's not much room in there so I'll check the best I can. I messed with again today and started on first try then died after about 30 seconds. One thing that is troubling is the last time I had issues I noticed a waxy build up on the top of the engine from the stator. I thought that was why it was running so rough. Turned out to be the trigger. Now I notice since the trigger has been replaced there's the same wax buildup on the the insulation of the wires coming from the trigger. So this stator overheating issue wasn't a one time thing so I have a feeling it will need replacing soon. At this point I don't think this is a stator issue as it is an intermittent problem and shouldn't force me to have to go wide open throttle to get it to start at times. I wouldn't think anyway...