1978 70 hp Evinrude Model 70873c update

[JZEVINRUDE]

Engine bogs down and stalls when under load, runs fine with the muffs. I have had the 3 carbs rebuilt, fuel lines and fuel pump replaced, leaf plate and manifold degunked and checked for cracks, new thermostat, new plugs, coils show good arc using the spark tool, compression is 115-115-110, plugs all the same color and wetness, this is very demoralizing. I have tried all suggestions any other ideas?

 

[jonesg]

Re: 1978 70 hp Evinrude Model 70873c update

Good compression.
Good spark, jumping 7/16" gap ?
Check ignition advance.

Also have you tried pumping the bulb when trying to get it going on the water.

 

[JZEVINRUDE]

Re: 1978 70 hp Evinrude Model 70873c update

The spark was jumping the gap on the plug tester with a strong spark. What do I do to check the ignition advance? Pumping the bulb does not help when on the water.

 

[jonesg]

Re: 1978 70 hp Evinrude Model 70873c update

How wide is the gap that the spark jumps?
Have you tried a timing light on it as it fails under load, that would indicate whether its dropping the spark.

The ignition is supposed to start advancing before the carbs open from idle.

Failing under load or bogging down can be spark (poor coils or plugs/wires) ,
poor carb work or weak pump. Fuel delivery ( clogged filters, clogged connectors, bad lines) .

It also depends on the engine history, was it running fine then just start going south or is it a new to you outboard, if its new to you I'd go through everything and set it all to original spec.

A factory service manual would help tremendously.
www.outboardbooks.com

 

[billy4hp]

Re: 1978 70 hp Evinrude Model 70873c update

Link and Sync???

 

[JZEVINRUDE]

Re: 1978 70 hp Evinrude Model 70873c update

The spark jumps the 1/2 inch gap on the spark tester tool. The lync was sync. I put in new fuel lines and pump. I have been going by the manual for all the work I have done so far! The problem has been on going for a few years but tolerable by just hitting the choke to get it going, but not anymore. It just has gotten worse.

 

[Gavin Crane]

Re: 1978 70 hp Evinrude Model 70873c update

I am having the same problem with mine right now. What did you find out about yours?

 

[mudtaz]

Re: 1978 70 hp Evinrude Model 70873c update

I have the same motor with the same problem. With the ears on or when it is not in gear it runs fine but as soon as it is in the water and put in gear it dies. Any suggestions?

 

[Anno]

Re: 1978 70 hp Evinrude Model 70873c update

Hi there I also have this same problem has anyone had any luck fixing have replaced coils and plugs re built carbs and done link sync also I've replaced stator also new fuel lines and pump and new tank pls help thanks

 

[joneill182]

Re: 1978 70 hp Evinrude Model 70873c update

Had the same prob with my 1975 70hp evinrude. Turned out to be a bad fitting on the tank, switch out the fitting for a new and it runs like a dream.

 

[countryboy_27205]

Re: 1978 70 hp Evinrude Model 70873c update

hey i have had the same prob. I cleaned my cabs real good and on mine it has a fuel filter built in on the motor it self befor it goes to the carbs. i took it apart and pulled the screen out and it was stoped up. just cleaned it and know it does just fine. hope that helps.