Thread: 1970's Johnson 25 horse losing power

Not a mechanic, BUT, indications point to MAYBE that your gas tank is not vented. Is your"bulb" collapsing prior to shutdown??

No sir. I checked that. I have been told to check for an air leak on my connections to the bulb, tank and engine for a loose clamp. I will check that today.

George if you don't find anything there you might pull the bowl off carb and pump bulb rel slow to see if your getting gas into the carb. I usually try to cut off a coke can to put under carb if possible to catch gas. Also need to check plugs for spark. It could be electrical also. Did it just die and not ever start again?

Does it do this every time?? Does it spit and sputter or just ease out kind of like idling down and finally die? How long until a restart is possible? Really sounds fuel starved. Do like cray said and take the bowl off. There is a rod and a needle inside the bowl on top of the float. Works just like the float in your toilet. The needle either has a rubber tip or there is an oring inside the inlet. Take the float off and pump your bulb. Allow fuel to flow through the inlet. I said something about the oring because if it has an oring inside the inlet and you pump the bulb it will blow it out and you'll lose it....don't ask how I know...lol. After you flush it put it back on and try it. You could have a piece of trash on in that inlet next to the needle. It has fuel when it sits but doesn't have enough flow to keep bowl full as you are running.

Its been a while and I do not remember if and where the fuel pump is. It will be a little square deal I believe it the model has one. It normally has a screen in it. The fuel lines will go in and out of this. There is a flathead screw in the center of it I think...or something similar. Take this off and make sure the screen is clean. Some also have a small inline filter on them...replace this.

Something else...while the bowl is off, take some compressed air....maybe 40 or so psi....not the 120 after the compressor shuts off, that will make a mess...lol. Blow air backwards through the fuel lines to the tank...slowly. That may dislodge something if by chance its in the line itself. Just some things to try...keep us updated.

The motor slows down and died, the one time. The rest of the time it would just slow down. I can restart it within a couple minutes. I have wondered if it just has some debris or junk in the carb and some seafoam might dissolve it out. I will attempt tp take it out on the lake again for another run with seafoam in it AND locate the carb and see iff some compressed air might dislodge any debris. I will install an in line filter too. The fuel line is a little stiff due to age so I might make another one just to satisfy myself. Stay tuned, I will report back soon.

Stiff fuel lines are not good. They can crack and allow air to be sucked in. Especially the primer bulb. It is the first to go.

+1 on what bill said. If its stiff get a new line, bulb, and connectors. Seafoam is a great product and its a good idea to run some often. Do a good decarb while you are working on the fuel system. Mix 3/4 of a can of seafoam with a gallon of gas and run it for a few minutes and stop and fish for about 15mins...do that until you run out of fuel. Then put the other 1/4 in a squirt can and spray into the carbs while you work the throttle then kill it for another 15 then hook your regular tank back up. That will dissolve most if not all the carbon build up on your rings and piston.

If you start it within a few minutes I really think it will be something in the fuel inlet system somewhere. Maybe at float needle...maybe in the line itself, like bill said it can suck air and you'll lose prime. You get to reading the forums and you'll find that ALOT of money and time are spent on fuel lines and primer bulbs...lol. Good Luck!!

I checked the fuel line today and there are no cracks in the line or bulb. I squeezed the bulb fairly hard and had a little gas come out of the connector going to the engine, that was all. I picked up some seafoam to add to the gallon of gas and will run that thru the motor maybe this week and see what happens.