How to test for strong spark ?

[pa eric]

Can some one tell me how to test for spark strength. I have a 74 evinrude 85hp that sputters to a stop after starting. Lots of fuel is there(hard bulb). I have spark to all four plugs but I'm not sure how much. It wil start quickly everytime only to sputter to a stop after a few seconds. I can restart it at will till the battery dies. Almost makes me think its shorting out from the vibration of running or weak spark after inital start up. Thanks for any direction you can give me. Eric

 

[tashasdaddy]

Re: How to test for strong spark ?

these are available at auto parts stores, adjust it to 1/2 inch. spark should be blue. have you check compression? do you use your choke when starting, and to keep it running until the motor warms up and settles. has this problem just recently started? read this:
http://forums.iboats.com/showthread.php?t=225510

 

[pa eric]

Re: How to test for strong spark ?

This all started last spring during a shakedown run before an annual fishing trip. I launched started and ran the boat for 15 min. at all diffrent speeds.It started to develope a miss at half trottle. After stopping and checking out the basics ( fuel, plugs ). It got steadly worse untill stalling completely. After killing the battery and rowing in i took it home and called my shadetree mechnic. Many hours and months later I still am still baffled. But, I did not check compression. I was thinking coil packs? Thanks Eric

 

[tashasdaddy]

Re: How to test for strong spark ?

it could very well be a coil or coils, heating up and failing, also could be a power pack heating up and failing. which you have to get the motor up to temperature and it fail again to find. by check spark on all 4.

also could be clogged vent on fuel tank, if the tank can't get air into it, the fuel pump cannot suck fuel out of a vaccum.

 

[ezeke]

Re: How to test for strong spark ?

The 1973 and 1974 V4 motors had an automatic choke function that often failed to work properly, engaging the choke at the wrong time. It was especially vulnerable to thermostat problems because it was activated by a temperature switch.

Most of the systems were disabled at the time by OMC service departments.

The temperature switch was/is located at the lifting eye between the cylinder banks. The wiring ran to the terminal block and controled the choke solenoid from there.

If you have a choke solenoid with three wires, two of which are purple, you may want to check to see that the automatic choke is disabled.