1977 70hp Stalls On Initial Acceleration

[racey70]

Hi I have a 1977 Evinrude 70HP. It starts first or second time from cold. I tilt the motor to take it to the water, it then appears to be flooded, since it takes a bit of cranking (and openning the throttle) to get it going. Once going it runs well, idles, accelerates and returns to idle. After about half an hour of running, it stalls at idle. I have to lift the warm up throttle leaver to fast idle it. When I move the main throttle slowy to go forward, it stalls. I have to re-start, fast idle then shove the throttle quickly open ( as you can imagine everyone nearly falls over!). I have adjusted the pickup timing per specs at 0BTDC. Any thoughts would be welcome? Thanks

 

[jtexas]

Re: 1977 70hp Stalls On Initial Acceleration

welcome to iboats!

you aren't starting the motor without supplying water to the lower unit, are you? that'll burn up the water pump.

worn float valves/seats in the carbs can flood it when you tilt it up.......try it with the airbox cover off, observe whether gas runs out the carbs when tilted all the way up.

was the l/u submerged when you set the timing? backpressure on the exhaust makes a difference.

engine dies on acceleration is a symptom of improper linc & sync...the spark advance should start before the throttle butterflies start to open.

make sure the timer base moves smoothly without sticking.

and make sure the choke butterflies are all fully open except when engaged.

 

[racey70]

Re: 1977 70hp Stalls On Initial Acceleration

jtexas, thanks for your advice. I use muffs out of the water, I did the timing on the muffs, will re-do in the water. Again thanks

 

[esmwolfe]

Re: 1977 70hp Stalls On Initial Acceleration

I had similar troubles on that motor myself. Turned out to be a bad head gasket for me. When yours stalls, pull the spark plugs and crank the starter. If you see water come out of one of the cylinders (probably bottom), that's the trouble. Took me months and months to figure it out.

 

[tashasdaddy]

Re: 1977 70hp Stalls On Initial Acceleration

also the problem does not start until after running for 30 minutes. this tells me that you should check your spark at that time, on all 3 cylinders, sounds like you have a coil heating up, and failing. thus running on 2 cylinders. when you shift it should be a quick deliberate shift. you do not ease these motors into gear. easing chews up the edges of the clutch dog. and will create lower unit problems, later.

 

[racey70]

Re: 1977 70hp Stalls On Initial Acceleration

Thanks for all the advice, I ran the boat last a couple of days ago. After a decent run I pulled the plugs & no1 was slightly blacker thatn 2 & 3 9which were the same). I had previously set the throttle roller in lign with the lower mark, but at idle the plate is touching the roller in line with/slightly above (1mm) in order to prevent it from stalling. All three carbs move at the same time and the timer plate moves a fraction ahead of the carbs opening. I will over the next few weeks do the proper lynch&sync, the pickup timing in the water and pull the plug leads to see if there is a dead cylinder Thanks again