1973 Johnson 65 Fuel pump question

[TampaNate77]

So I have been having the hardest time trying to figure out why I have no power at WOT, and why I cannot get off plane. I rebuilt all 3 carb's.... Float adjustments are correct, and I have 125 psi all 3 cylinders. But I still get fuel coming out of the carb's once the motor is turned off, and it runs like crap in the water.... and at WOT the boat will not come off plane. So I took the fuel pump apart and found out that the diaphragm in it was so cracked that the plastic housing inside the fuel pump broke apart. Could this cause all of my problems? Can a fuel pump cause it to leak fuel and run that bad out in the water?

 

[fireman57]

Re: 1973 Johnson 65 Fuel pump question

Yes it can but fuel coming out of your carbs indicates that you have a float that is not closing all the way.

 

[TampaNate77]

Re: 1973 Johnson 65 Fuel pump question

Yes it can but fuel coming out of your carbs indicates that you have a float that is not closing all the way.

They are closing all the way.... I have taken the carb's apart 7 times because I keep thinking it's the float adjustments and everytime I take them off the floats are all closing the way they should. And all 3 carb's have new needle valves and seats... And I cleaned the crab's thoroughly after taken them apart. So you don't think a bad fuel pump would cause fuel to leak out of the carb's?

 

[fireman57]

Re: 1973 Johnson 65 Fuel pump question

It shouldn't because it is no longer pumping when the engine is shut off. there is a pulse hose on one nipple of the fuel pump. Make sure that it is not clogged for some reason. Maybe it is keeping pressure after the engine is shut off. Also make sure that the fuel tank vent is clear.

 

[Aussie Rob]

Re: 1973 Johnson 65 Fuel pump question

It could also be the reed valves. they may not be closing (lost their spring - if you have the carbies off you should be able to see them. they should be closed if they are partly open they need replacing.

 

[emdsapmgr]

Re: 1973 Johnson 65 Fuel pump question

It's not unusual for some fuel to leak out the carbs on those older engines, esp if the engine is tilted up after using. My 72 100 hp was a leaker, so was my 76 135. That's why there is a drain line in the airbox-to recirculate the excess carb fuel back into the engine at each startup. An original fuel pump on that engine was not made to handle today's ethanol fuels. The ethanol will attack the all the rubber components of a 1973 fuel system, including the fuel pump bladder. If the pump is damaged, it likely won't pump enough fuel at WOT in order to provide an adequately supply fuel for the 3 carbs. Probably time for a new pump. A new pump will have 2013 ethanol-compliant components. I'd also be concerned about fragments of any original fuel hoses breaking away and migrating into the carbs and possibly sticking in the jets, causing running issues, even a lean condition.

 

[kenmyfam]

Re: 1973 Johnson 65 Fuel pump question

+1 on the above (post #6)

 

[Faztbullet]

Re: 1973 Johnson 65 Fuel pump question

How much fuel coming out??? Like previous posting stated you could have debris in fuel especially under fuel inlet needle causing it to stay open. Did you float test the floats as they may also be ethanol damaged and get heavy and sink causing it to flood

It could also be the reed valves. they may not be closing (lost their spring

Sorry Rob but reeds will not cause flooding and they do not loose their spring, and they can stand open by a couple of thousands....

 

[ezmobee]

Re: 1973 Johnson 65 Fuel pump question

Old thread gents.......