1974 Johnson 25hp 25E74M- Misfire

[shad309]

My old motor is giving me some fits and I'm looking for any advice. I'm not a mechanic but I can do simple maintenance and repairs.. However, this thing is kickin my butt! I have replaced the plugs, plug wire and coils, new fuel tank, lines and fittings as well. The motor will idle then has a miss that will bogg the motor down for a second and tries to recover but hits another misfire and dies when in the tank. On the water I opened it up and at first ran great for about 5 seconds then the misfire situation and then it would run at about 1/4 power at full throttle. If you let off it will die. I forgot to take a video on the water but I do have one in a tank.

Any and all advice will be greatly appreciated! https://youtu.be/m4CgucHyCmw

 

[oldboat1]

I would suspect a fuel pump issue -- typically needs a diaphragm. Try squeezing the primer bulb and see if you can keep it running that way.

 

[shad309]

When I ran it on the lake I could feel a little surge when I pumped the primer bulb but was very slight. If I'm running at idle, in the tank, and I squeeze the bulb it doesn't seem to keep it from misfiring and dying. I plan on doing a decarb with seafoam tonight and run some thru the carburetor too.
I'll order a fuel pump kit and see what happens. Thanks for the response!

 

[F_R]

Yep, it is lean-sneezing and quitting from lack of fuel. Make sure the o-rings are good in the tank hose ends, and make sure no leaks where hose plugs onto tank.