Old school Thunderbolt question...420HP
 

Do the old schollignitions on 420 boats use internal or external resister coils?

HAving lots of wierd ignition issues and wondering what coild I am supposed to have??

Or if my issue coulkd be in the wring harness (resistor)??

420 hp w/ thunderbolt iv has internal resistor coil. Look at the Doug Russel website and go through the parts book to figure out what you should have

Your boat being a 1985, probably came with a points style ignition. Its possible theres a resistor in the wiring harness. Make sure you have a full 12+ volts at the coil with the TBOLT IV.

Right, when I bought the Baja it had points, I converted it to TB ignition and always have been having spark issues, but had lots of other issues over the years to deal with and now that I put it all in Cig same issue is there...

12 at the coil? or ACROSS the coil?

if it has resistor where would it be? I used the stock points harness years ago in it, can I remove it?

Odd thing is I did both engines at same time 4 years ago, port always is fine, stbd not, but I look at spark and port spark looks way stronger then stbd...

so if there is a resistor how can one be fine and other not????

12v at the positive side of the coil, resistor wire would be in the harness with another wire coming from the "I" terminal on the starter.

dont overlook your ignition switch itself going bad. That was a common occurence on the old Parasail boats i had over the years.When they get old they can not be making good contact and have the same issues you are describing.

Right.... same issue..... different boats.... wiring followed engine from Baja to cig..... I put new ignition switches in Baja to check when I had issues there

Btw if the resistor wire is still in the harness you'll have 5-7 volts key on and 12 while cranking

I checked lacrosse. Coil once and it had 7 volts.. I did other engine it had 12 how come one one was right and one wring when. Other were points before I changed it?

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