'77 Johnson 70hp, stalls when accelerated

[Clint F.]

The engine starts great and runs fine at idle or slightly higher, but when I try to accelerate, the engine simply dies. About 50% of the time, I can squeeze the bulb until hard (while running), and it will accelerate and run as normal. Occasionally, the engine will falter at high speed, gradually dying. When this occurs, the bulb is run flat.<br /><br />I tried disconnecting the crankcase line from the fuel pump, and there is no change in operation (?????). There is fluctuating pressure on this line, however.<br /><br />I have replaced the fuel line and bulb (OEM) with an aftermarket unit (Tempo), dis-assembled and examined the fuel pump (seemed ok), and finally replaced the fuel pump (with OEM part). No improvement. I have two fuel tanks, and the problem occurs with both. Fuel is fresh.<br /><br />Any advice would be very much appreciated!!!

 

[blueboat1]

Re: '77 Johnson 70hp, stalls when accelerated

Sounds like you covered all the things that I would have looked at. It sounds like an air leak in a fuel line or the pump (which you said you replaced). I would get all new fuel lines for each carb. It’s cheap and if it doesn’t fix it you at least you haven’t blown a ton of money. My merc did that and it ended up being a fuel line to the carb had a pin hole. Good luck

 

[Clint F.]

Re: '77 Johnson 70hp, stalls when accelerated

Thanks for the advice, Scott...I'll try that for sure. Also, in the 1st paragraph wher I said the bulb "runs flat", I should have said "runs empty"

 

[Brew]

Re: '77 Johnson 70hp, stalls when accelerated

Possibly a tank venting problem? Could try running with the tank cap off to see if there is any change.<br /><br />Good Luck!

 

[Clint F.]

Re: '77 Johnson 70hp, stalls when accelerated

Thanks Brew...I checked that and forgot to mention it. Venting seems normal on both tanks.

 

[twofishy4u]

Re: '77 Johnson 70hp, stalls when accelerated

try using an omc gas line I've had this same issue occur twice with tempo gas lines. The five dollars you save isn't worth it.

 

[Clint F.]

Re: '77 Johnson 70hp, stalls when accelerated

I have not seen any leaks in the fuel line. Would a "pin-hole" leak cause the failure I describe? I sure would replace the fuel line again, but prefer not to. Should I look for a leak between the tank and bulb, bulb and motor, or fuel pump and carbs? Or any of the above?

 

[Clint F.]

Re: '77 Johnson 70hp, stalls when accelerated

Any more advice??? I replaced all the fuel lines on the engine, and replaced the Tempo fuel line and bulb...no real improvement.<br /><br />I'm reaching the end of my rope, guys!!! This should be something fairly obvious, right?!?!?!?

 

[Clint F.]

Re: '77 Johnson 70hp, stalls when accelerated

I had the boat to the mechanic. They cleaned and installed carb kits in all three carbs. I took back the boat, and it seemed to run fine. The next day...same old problem. Runs OK when first started, but if I shut the engine off to fish, when I attempt to accelerate, it dies.<br /><br />Could this be a timing issue?<br /><br />Please advise, I am perplexed. I need some of you OMC experts!!!

 

[Solittle]

Re: '77 Johnson 70hp, stalls when accelerated

Have you replace the connectors for the fuel line both at the tank and the motor? They have small orings inside that can leak air. You can just replace the o rings but they are a pain.