1973 50hp Johnson keeps stalling!

[mickarch]

So I have a 1973 50hp Johnson model #50ESL73R that just won't stay running. I did some searching here and found that I should pump the primer bulb when it starts to die to see what happens. Pumping the bulb brings it back to life, so I figured the fuel pump may be at fault.

I ordered and installed a new fuel pump and all new gas lines under the cowl while I was at it. The lines from tank to motor are less than a year old, and work fine with my other motor, so I figured they were ok.

Well, I got it running again and sure enough after about 3 minutes of idling, it dies. Pump the bulb and it comes back to life.

So, I'm stumped. One thing that seemed odd is that the replacement fuel pump was not exactly the same as the original, only 2 of the 3 mounting screws lined up with the holes in the silencer. All of the hose connections were the same though. I just figured the original part was superseded by another that was slightly longer than original.

Anybody know what I should look into next? When it is running, it runs great, just gets starved for fuel even with the new pump and lines. I'd love to get this fixed quick so I can get a few more days on the water this season.

I need help!
Thanks,
mick

 

[tashasdaddy]

Re: 1973 50hp Johnson keeps stalling!

stuck float needle valves, pumping the bulb force fuel thru them, but the pump pressure is less than the hand pump. carb cleanings in your future.

 

[mickarch]

Re: 1973 50hp Johnson keeps stalling!

Ahh, I hadn't considered the carbs since it was running so well once I pumped it full of gas. I'll tear them down first this tomorrow and clean them up, can't do it tonight, kids are going to start showing up soon for candy .

Anything in particular to look for besides the float needles while I'm in there? Anything else I should be checking in addition to the carbs? I can't think of anything else it could be. Does anything ever go wrong with the fuel connectors either the 2 on the gas line, or the one mounted in the engine?

 

[JIGGER]

Re: 1973 50hp Johnson keeps stalling!

Make sure you use carb cleaner and the straw that comes with it. Blow through all the passages and verify good fuel flow to them. Might be sucking air too. Also might pay to take on carb apart at a time. Gives ya something to remember.

 

[CharlieB]

Re: 1973 50hp Johnson keeps stalling!

You may have air leaking into the fuel line at the fitting to the engine.

Test by installing a temporary clear hose between the fuel pump and carb, watch for any air bubbles while running which indicate air sucking in somewhere between the bulb and the pump.

 

[tashasdaddy]

Re: 1973 50hp Johnson keeps stalling!

it sounds like it is burning the fuel in the bowls, and not refilling. read this

http://forums.iboats.com/showthread.php?t=244013

 

[mickarch]

Re: 1973 50hp Johnson keeps stalling!

Thanks for advice and link. I've rebuilt motorcycle carbs before and also the one on my 35hp merc, so I'm thinking it should go pretty smoothly. I'm hoping I can pick up rebuild kits at Napa so I don't have to wait on delivery.

Once the carbs are cleaned up, I'll try the clear tube to make sure there aren't any air leaks.

Thanks for the advice everyone!
mick

 

[mickarch]

Re: 1973 50hp Johnson keeps stalling!

Ok, so I took apart the carbs and there were actually pretty spotless inside, but the float needles were a little worn. They were not stuck though, floats and needles moved freely. But since there were apart and I had the kits, I replaced the floats, needles and seats. Then put everything back together and hook up the clear hose between the pump and carb as was suggested and start turning the motor over.

Well, it the clear hose revealed that the new pump was not pumping. In looking at the hoses (3 hose pump), there is a fuel in, fuel out, and the vacuum line. If you look at the attached crude diagram of the front of the motor, the vacuum line was hooked to port A. Port B was hooked to the silencer in front of the carbs.

Since I couldn't think of anything else to do, I attached hose B to the pump and turned it over, and sure enough it pumped gas.

My manual does show the proper configuration of the hoses, but I originally had it hooked the way it was when I got the motor (A to pump). But switching to hose B on the fuel pump seems to get it working, whereas hose A did nothing.

Does anyone know if hose B is supposed to be on the pump and my problem is fixed, of if hose A should and there is something else wrong?

I'm so confused...

 

[mickarch]

Re: 1973 50hp Johnson keeps stalling!

Well, I think I've figured it out. The only thing left that it could have been was an obstruction inside the motor, so I pulled off the intake manifold.

Sure enough there was a blockage. It looks like the previous owner, who must have owned stock in an RTV company, used an incorrect gasket that did not have a hole where the vacuum nipple was for the fuel pump. It was completely blocked. I don't know how they kept the motor running, must have been with an external fuel pump or something.

Anyways, new gaskets on order, so looks like another week of waiting for the parts to arrive.

Hopefully this will take care of it.

Thanks for the guidance,
mick