Early 80's Johnnyrude dies on deceleration

[Blue_Runner]

Need help with a buddy's 1983 Johnson 15 hp tiller steer. Motor runs and idles strong. The problem is sometimes when running near WOT, when you go to back off the throttle she cuts out and cuts off - even when you gently pull it back (most of the time) while pumping the bulb. I've suggested eliminating all of the simple stuff like, try a different fuel line/primer bulb fuel tank, reset the idle jet needle, swap the fuel pump with the one from my 9.9 to see if that fixes it, etc. Anybody experience this and/or have any suggestions? Time to rebuild the carb?

Edit: one thing I noticed is when you squeeze the primer bulb real tight, some fuel will leak through the fuel line connector connected to the engine. That doesn't seem normal to me and seems it could cause a vacuum leak?