mercruiser 255 inboard 3.4 volts to coil wire

[kmarine]

I am working on a 1979 harbormaster houseboat with 5.7 liter 255 hp inboards with v drive. (post engine swap using original Mallory type distributor with new points, coil and condenser.)
I can only start and run engine by jumping the +coil to the positive battery post.
At the key switch I have 13.4 volts however the resisted coil wire reads inconsistant from 12 to 3.5 volts as the points open and close. The double wire also is connected to the starter solenoid which is supposed to bost the coil to 12volts when cranking engine. When the engine is cranking with the coil +wire not connected I do not get the added boost to fully power the coil during starting . After i jumped the to positive battery i was able to set timing and adjust carb. With the key switched in the run position the engine dies after disconnecting the coil +jump wire to battery. Hate to tear appart wire loom, however which color wire is the ignition wire in the loom and what size resister /resister coil do i need to bypass resister wire. Thank you in advance.

 

[Scott Danforth]

verify your wiring, you have something not connected and it sounds like a bad connection somewhere

you should have about 8-9 volts on the resistor wire

there should be battery voltage on the lead coming from the R terminal on the starter only during cranking

did you set the points with a dwell meter? what dwell are you getting?

 

[kmarine]

I am getting voltage to the R terminal during starting ( 10v) at the solenoid not the wire end to coil. I am going to have to open the loom by the connecter and see if i have a pinched or broken, or grounding coil wire next. my dwell meter stopped working yesterday too. (sitting too many years in the bottom of my tool truck) I am thinking my next mission is to separate the two wires crimped together at the coil and test individually. My other stumped mechanics here are curious to see what also I find. Thank you for your response.

 

[Scott Danforth]

If you are only getting 10 volts at the R terminal, either your battery is toast, your battery connections are bad, your battery cables are bad, our your starter solenoid contacts are arced over

With good batteries and good cables and a good solenoid, you should be getting 13.4 volts when the contact first pulls in, then about 12 volts when the engine is cranking

 

[kmarine]

It seems I have a lot of cleaning of contacts and connectors to go through in this 40 year old wire loom. The other engine has been converted to Mallory electronic ignition coil and pickup. one of the other mechanics has donated an old stock new in box distributor and coil with electronic pickup (cleaning out his garage). I have 13.4 volts at the purple ignition wire so I am updating to a more powerful ignition system after I purge the water and old fuel from this neglected fuel system. will replace it with rec 90 ethanol free fuel and filters. Sorry for the delay on posting had a few other boat emergencies to tackle. It amazes me that people think we can get to repairing their boat ahead of people waiting weeks.

 

[kmarine]

Just posting to update that the boster wire from the starter solenoid (I) terminal to the coil shorted and was drawing excess current from ignition wire. Isolated short and repaired loom. on to the next not running boat.