johnson 65es72 fueling problems

[andywhite]

hi there, the 65es72 ive had for a couple years now decided a week ago to leave me in the middle of the lake. not fun paddling a 17.5ft tri hull in 15k wind. the problem is.. took it out 3 times now, first time ran like a trooper, the second time ran out of fuel, so switched to the other tank, primed the ball again and she fired right up, but it ran for 10 seconds then quit. couldnt get started so paddled back after battery died. after tinkering with it, got it started at home thoiught all was good but no luck. i figured could be air locked so put gas in the cylinders and finally it went. everything was good, but took it out again and made it 500 yards then it quit with the same problem. tank is full, ball keeps its prime. dirty carbs maybe?? fuel pump??, any suggestions much appriechiated

thanks
happy boating

 

[Joe Reeves]

Re: johnson 65es72 fueling problems

The fuel primer bulb (normally laying horizontal) should not stay hard when the engine is running. It is the nature of the beast, so to speak, that the fuel drops down to the halfway point of the bulb. If it stays hard, possibly the output valve of the bulb has come apart and is being drawn reversed back into its shell which effectively causes it to be a shut off valve.

If the bulb valves are okay, have someone pump the bulb constantly, acting as a manual fuel pump. If this corrects the problem, suspect a failing fuel pump.

Keep some equipment in the boat so that you can remove the spark plugs and quickly check the spark to see that the spark exists and will jump a 1/4" gap with a strong blue lightning like flame... a real SNAP! A small or medium size philips screwdriver jammed into the plug boot and held away from the block will suffice as a gap test. Let us know what you find.

 

[andywhite]

Re: johnson 65es72 fueling problems

thanks, when it was running the ball didnt feel, rock hard, it was as you said half full, my mistake. as for pumpinh the ball as a manual primer, that didnt help the motor still cut out. theres great spark on all 3 cylinders. although i did notice whilst trying to start it, pumping the ball and turning it over and over, the plugs were still dry, and cant smell any fuel in the carb intake, the screen in the filter looks clean.

thanks in advance
happy boating

 

[Joe Reeves]

Re: johnson 65es72 fueling problems

Normally, when carburetors become fouled, the engine will have a strong tendency to bog down and die out when throttle is applied, but you haven't mentioned having that problem.

However, assuming you have compression and proper spark... that leaves fuel. But before going in to the fuel section, check the compression which should be aproximately 100+ and fairly even on all cylinders. What did you find?

If the compression is okay (have rags and a container handy), remove the carburetor face plate, then remove the bolt/screw that you'll see at the front bottom portion of each float chamber. Check for water in that fuel as it's always possible to purchase contaminated fuel. If the fuel checks out okay (no water), again assuming that the spark and compression are as they should be, the next step would be removing, cleaning, and rebuilding the carburetors.