81 evinrude 115 only starts at near full throttle

[JST0771]

Last year I thought I had everything buttoned up on this project. I was out on the lake running @ wot for about 10 minutes. No problems self launching the boat. It started normally off the trailer and when I came back from parking the truck. After about 10 minutes I stopped it to make a call. I waited a few minutes for some friends to catch up with me in their boat. When I tried to start the engine it just turned over. Just before I killed the battery, I tried advancing the throttle and it started just before full throttle. It will not stay running if I pull the throttle back to idle.

I don't have a neutral safety switch. I putt it in gear full throttle and it started and launched out of the water. So to speak. Got it back to the dock it it died trying to get it in reverse. It sounded really rough. I also noticed on the trailer I hit a log and bent a fin on the prop.

Last weekend, I finally felt like messing with it. I found and replaced 2 cracked fule lines at the primer solenoid. Got it started but there was no water flow. That turned out to be the **** hose being clogged with crud. Cleared it and good flow again.

Same issue as last year when took it off the lake as described above. Any advice where to start?

 

[racerone]

Compression test is the first thing to do on these crossflow motors.----They are famous for suffering from broken piston rings.

 

[keefallan]

I was gonna suggest the same thing.......start with a compression test and go from there

 

[Calebwitdafro]

Definitely sounds like a fuel problem. With the engine nearly wide open it is opening the throttle plates to allow more air. With this allowing the engine to start, it tell me you have a fuel restriction. First step for me on an issue like this, is to rebuild the carbs. Cracked fuel lines to the primer solenoid could also indicate you have a faulty primer dumping fuel into the carbs at all times which could be counter acted by opening up the carbs to more air. Unlikely, but possible.

 

[racerone]

How can cracked fuel lines to the electric primer valve dump more fuel into the engine ????

 

[ct1762@gmail.com]

sounds like you lost a cylinder or 2, and NOT because it's getting too much fuel. compression test, spark gap on each cyl and report.