850 thunderbolt ignition probs

[scottmildy]

My 74 850 thunderbolt is having ignition problems. Sometimes it works and sometimes it dont. mecury switch unhooked, neutral safety switch replaced, CDI box replaced. Has nothing to do with heat....will work for 5min then boom dies. will work fine for half a summer then decide to quit. Have had it into 3 different marine mechanics but it still dies. Anyone know of known issues with this engine, or where I should start.<br /><br />Greatly appreciated

 

[Ben Konopacky]

Re: 850 thunderbolt ignition probs

for starters when it dies you have to check for a problem at that time.start with batt. voltage at the box (switch box) when cranking.Min.9.5v,have spark,gas? check tomkatesam post on an 850/75

 

[scottmildy]

Re: 850 thunderbolt ignition probs

Thanks for replying Ben Lucky. I know its ignition, for the fact that you could be clippin at half throttle and it will just die, no spudder at all. crazy thing is my dad just got it started this weekend like nothing ever happened!!! I think I am gonna replace the wiring harnass, then who knows.

 

[Chris1956]

Re: 850 thunderbolt ignition probs

74 - If that motor has a distributor, then the ignition switch supplies +12V to the white terminal on the starboard side of the switchbox. If you suspect that the ignition switch is intermittent (it may be), you can connect the white terminal on the switchbox to the red terminal above it with a jumper wire. This will eliminate the effect of the ignition key.