1972 50hp Johnson fuel issue

[Gooseman4506]

I have a 72' 50hp Johnson that isn't getting any fuel past the carburators. The pump is pumping fuel and both of the carb bowls are filling up but it's not going any further than that. I've ordered a new pump just in case it's not providing enough pressure and both carbs were rebuilt. Now I'm just at a bit of a loss and don't really know where to turn from here. Any help would be greatly appreciated, and thank you in advance

 

[F_R]

Re: 1972 50hp Johnson fuel issue

If the float bowls are filling up, the only thing beyond that would be the high speed jets in the bottom of the bowls.

 

[Gooseman4506]

Re: 1972 50hp Johnson fuel issue

Thank you for the response, I didnt mess with the high speed ports because I was under the impression that they weren't adjustable or anything. Ill get the carbs off again and check it out and post back with the results. Think you again for the help

 

[Gooseman4506]

Re: 1972 50hp Johnson fuel issue

I cleaned the high speed jets and now I can get it to stay running for a few minutes but then then idle starts going up and down and it dies out. I don't really know all that much about boat motors so I'm not real sure where to go from here.

 

[F_R]

Re: 1972 50hp Johnson fuel issue

Well as I keep preaching, a great diagnostic tool is a fuel pressure gauge. You temporary tee it into the hose between the fuel pump and carburetors. That will monitor the fuel pressure as it runs. Doesn't cost much. Or you can start guessing and replacing parts. Fuel pump is suspect, but test first, spend later.

 

[boobie]

Re: 1972 50hp Johnson fuel issue

What have you got the low speed adjustment needles set at ??

 

[Gooseman4506]

Re: 1972 50hp Johnson fuel issue

They are both set at one turn out. I just remembered the vaccum hose lookin thing at the bottom of the crankcase is split at one end. Would that cause any problems with anything?

 

[boobie]

Re: 1972 50hp Johnson fuel issue

Try 2 1/4 turns and see what happens.

 

[Gooseman4506]

Re: 1972 50hp Johnson fuel issue

Ok ill try that out this evening after work. What kind of fuel pressure should i be seeing? I wouldn't imagine a diaphragm pump like that would put out much.

 

[F_R]

Re: 1972 50hp Johnson fuel issue

Tested on a boat or in proper test tank with test prop, with tank cap loose, expect 1 PSI at idle, 1.5 PSI at 3000 RPM, 2.5 PSI at 4500 RPM. That's from the factory service manual.

 

[Gooseman4506]

Re: 1972 50hp Johnson fuel issue

Ok i can keep it running now i just need to put it in the water and finish tweaking it. Thank yall for all of the help and quick responses i really appreciate everything