ignition help again!

[rewdan]

you guys have helped me many times before so I thought I might try again!
I have a mercruiser 4.3 thunderbolt with no spark at the coil. I have changed the coil, plugs, cap, rotor etc. I think the only thing I haven't changed is the HT leads which I will do next,
But I am getting no spark when I put a plug in the lead from the top of the coil and turn the engine over.
I am also getting 12v from the positive terminal to ground on the coil when the ignition is on and from the negative terminal as well. The 12v remains if I turn the engine over.
Any ideas?
Thanks in advance

 

[Don S]

Re: ignition help again!

Thunderbol IV or V ????? Serial numbers are a good thing if you aren't sure.

 

[rewdan]

Re: ignition help again!

sorry iv , any ideas?

 

[rewdan]

Re: ignition help again!

just looking at a wiring diagram and there is a shift interrupt switch which could be jammed, could that be it ?

 

[Don S]

Re: ignition help again!

Here is the troubleshooting chart that should take you right to the problem.

 

[rewdan]

Re: ignition help again!

Thanks for that.
i dont have a spark gap tester and can't get a new set of ht leads until the summer here as my boat is in Ibiza (spain) and I need to return to the Uk on thursday and won't be back until the summer. They can't get me a set of leads until next week and I won't be here. I was hoping not to leave it until the summer if someone new the symptoms re the positive 12v at both terminals of the coil.
It could turn out to be the master lead from the coil is rubbish and then I wouldn't get a spark no matter what I tried but I don't know due to this island not holding stock of replacement leads!
Any ideas appreciated.