1976 Johnson 85 hp stalls out but will run if I flick choke on & off over & over

[andrewcraig]

I recently bought a boat with a 1976 Johnson 85 HP. The motor had signs of overheating which had me worried but after I rebuilt the lower unit (water pump, etc -- the cause of the overheat -- a rusted out iron key), rebuilt the two twin carbs, cleaned up the motor and connected the battery I tried to fire it up. With the first turn of the key and electric choke, the motor fired right up (using rabbit ears of course for cooling water).

The problem is that after five to ten seconds the motor loses power and loses rpms and finally dies out and stalls. It does this with the start lever in any position (slow, fast, anything). Oddly, I can keep the motor running by toggling the electronic chock on and off. I can keep it running for as long as I want, at any RPM with this technique. Even with the motor warm, if I stop flicking the choke on and off, the motor loses power and stalls out.

Any Ideas? I am going to buy a pressure tester to see what the 4 cylinders are at and I am about to order a fuel pump kit to see if it helps. The gas is brand new, the mixture 50/1 and the the bulb/hose is new. Is this a fuel problem, electonics problem? I stongly suspect fuel and or air mixture. There is a 1 on 50 chance I mixed up the orifices while rebuilding the two carbs but while toggling the choke, the motor, besides the rpms bobbing up and down as I choke it with the switch on the controls, seems to run great in terms of timing and compression.

Any help would be great.

Help, please. I want to go fishing.

Andy Craig

 

[JB]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Either unsuccessful carb cleaning or fuel supply failure.

Check fuel tank vent, restrictions or air leaks in the fuel pickup and lines, fuel pump.

 

[rootforvols]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

I had a similar problem this weekend. Ran fine for first
30mins or so. Stopped for about 40mins then started riding again. Ran for about 10mins at 3000-3500rpms then dropped to 2000rpms at full throttle, felt like I was pulling a train. After removing my fuel tanks when I returned home, realized the pressure release caps were still closed. Was this causing such a vacuum that the fuel pump was not able to pull fuel to the carbs, causing loss of rpms and power? Some guys at work feel this was the problem. Anybody else?

 

[rootforvols]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Failed to add I recently purchased my boat-1978 Bonito trihull w/ 1979 Johnson 85hp V4.

 

[Joe Reeves]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

If pumping the primer bulb fuel pump (acting as a manual fuel pump) has no effect, then as JB suggests you've overlooked something in the carburetors.

If you did not remove and manually clean the 2 high speed jets in each carburetor (4 total), do so.

 

[ezeke]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

I recommend that you take the side covers off the low speed jets and clean those as well.

 

[KYHunter2]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Rootforvols,

In the future, you'll get better results by starting your own thread.

Yes, not having your tank / tanks vented , will cause fuel delivery problems.

KYHunter

 

[adam1psu]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

same thing happened to me when i first threw my boat togther. turns out there was a mud wasp nest in the air vent. it ran fine after i cleaned it out.

 

[andrewcraig]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Well, I changed the fuel pump, the vent is open on the tank, even if I manually pump the bulb -- well the engine does the same thing although it seems to stall out a bit slower. I had cleaned the four orifices well (blew high pressure air/carb cleaner aerosol through them while in hand). I am going to check the cylinder pressure just to see what is going on there and am thinking of doing what a mechanic suggested -- temporarily changing the fuel lines out with clear plastic to see what is going on with any air in the lines. If there is no air, then it is back to the take the carbs apart again altough I did a pretty nice job (having worked on Ducati bikes for a long time)

By the way, the motor did this before I took off and cleaned the carbs (having just bought the used boat on Ebay). I was stunned to see the same problem afterwards.

I am also going to try another gas tank. Any more suggestions?

Andy, not fishing, just tinkering at this point.

 

[ezeke]

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Re: 1976 Johnson 85 hp stalls out but will run if I flick choke on & off over &

Check that the carburetors are tight against the intake manifold.

Running with the choke sure sounds like a lean condition and that often is because of an air leak. It can be because of a stuck float valve though, or something else restricting the fuel flow.

Are you getting any blow-back through the carbs?

Easy way to check the fuel pump is to get a portable tank and set it higher than the engine. All the fuel pump does is keep the float bowls full, and gravity can do that.

BTW, how far below the engine is your fuel tank?