1970 25 HP Johnson Seahorse fuel problem. Please help!!

[ranger460]

I have a 1970 Johnson 25 hp outboard with a real problem. When I start the engine, it will run for a 1 or 2 minutes at best, but then stalls. The exhaust is so rich that it burns the eyes. In an effort to figure out the problem I have found that there is a vacum line ( at least that's what I think it is) that runs from just below the fuel pump, to a port that is right next to the carburetor. If I pull this line off while it is running, it is spitting out gas and it is also coming out of the port by the carburetor. This has got to be wrong! I asked a local boat shop what they thought the problem was and they said the needle and seat was most likely the culprit. I replaced them, and the problem hasn't changed in the least bit. While I am a pretty good mechanic normally I have to admit that I am at a loss with this 2 stroke engine and I need help. If you have any ideas that may help me I would greatly appreciate it.

 

[sheboyganjohn]

Re: 1970 25 HP Johnson Seahorse fuel problem. Please help!!

I don't know that motor, so this is just a wild guess, but if the fuel pump is operated by vacuum, you could have a bad diaphragm in the fuel pump causing the motor to suck the fuel in through the vacuum line. If you go to the shop.evinrude website you can see the schematics for you motor and get a better idea. I am sure someone with more knowledge will pipe in.

By the way, welcome to the boards.

 

[Rick.]

Re: 1970 25 HP Johnson Seahorse fuel problem. Please help!!

I was already thinking needle and seat before I finished your post. What about a water logged float or an improperly adjusted float? That would have the same effect as a needle and seat not closing. Rick.

 

[ranger460]

Re: 1970 25 HP Johnson Seahorse fuel problem. Please help!!

I replaced the float when I rebuilt the Carburetor and the float was adjusted to the correct level. 3/4 of an inch as specified by the rebuild kit. I am thinking that it may have something to do with the fuel pump, because of the gas coming through the vacuum line that attaches by the fuel pump.

 

[ranger460]

Re: 1970 25 HP Johnson Seahorse fuel problem. Please help!!

sheboyganjohn,
Thanks for the welcome. Yeah it is a vacuum operated fuel pump, and I have been thinking that it could be the fuel pump but I wasn't sure and was hoping to get info from someone with more knowledge on the subject. I will check out the website you suggested.

 

[Mas]

Re: 1970 25 HP Johnson Seahorse fuel problem. Please help!!

When the motor is about to stall, pump the bulb on the fuel line from the tank to see if the rpms increase. If it does, I would start thinking about replacing the pump.

MAS

 

[ranger460]

Re: 1970 25 HP Johnson Seahorse fuel problem. Please help!!

"Mas";

I have tried that with the fuel bulb in the past and it has kept the motor running. Which pushed me in the direction of the fuel pump before. Your mentioning it reinforces that idea.

As sheboyganjohn suggested I went to the shop.evenrude site and looked at the blow up of my engines power head. The hose that I mentioned in my first post is listed as an "oil line" and it is connected to the "lower bypass cover". The fuel pump is also connected to this bypass cover. Anyone understand what is going on in this cover? That might be helpful.