Electronic Ignition Upgrade Recommendations 84 351W

I have a 1984 Supra Rider with 351w with prestolite distributor (I think this is original). About 3 years ago I replaced the points, condenser and cap. Went to fire up the boat after its long winters nap this weekend and couldn't get it to fire. Have spark and fuel but the spark at the plug looks weak. I replaced the coil which had a lifetime warranty but no luck. I am still running points and condenser and suspect I need to replace both. I saw a very weak and intermittent spark between the points. I have delayed putting in an electronic ignition for years but I think it is time to do the upgrade.

I wanted to check with those on here that are running a 351 that have made the change. Do you have any recommendations on what distributor to go with. I am thinking of replacing everything as I suspect the original distributor is worn. Looked at a Petronix Flame Thrower plug and play and saw people had mixed reviews on here about them and their products. Price looks good. I am looking for a good solution with strong tech support as I am not an expert at wiring and dealing with PO wire jobs and not sure what is correct.

I welcome your recommendations!

thanks
Dan

First the points should be replaced every season so you are on borrowed time anyway. I have changed out all my boats to a D.U.I. HEI ignition system. The system comes complete with coil . Easy 2 wire hook up 1- 12v hot and 1- tach lead you will need new spark plug wires and reset the spark plug gap to .045 . Summit has them [Davis Unified Ignition M35820BL -Marine Performance D.U.I. Distributors] They are also available other stores make sure you get the marine version.

Thank you Michael. As always, I appreciate your knowledge and insight into these old boats.

Hi Michael,

I ordered the DUI M35820BL and new wires from Summit and received it yesterday. I have been reading through the instructions and looking at some old wiring diagrams. What I am finding looking at mine and looking at my neighbors Ski Centurion, their have been changes to his and mine and noticing a lot of differences. I have a few questions and have attached some pictures. One of the things that i have been dealing with is a starting solenoid for years. It goes bad and has to be replaced. my neighbors doesn't have it anymore and is wired to the solenoid on the starter. I have left it as I found it because it works and didnt want to mess with things not knowing exactly what i am doing. Take a look at the pic. Have you come across these on your boats? My plan is to leave it on. Here are my questions

1. Reading the DUI instructions it calls for a 12 gauge wire from the ignition switch to the positive side of the distributor. My question is, can I run this wire from the positive pole of the starting solenoid? I believe this will then allow the distributor to work off of the ignition switch.

2. I have also attached a picture of my coil, which I think maybe wired wrong for the Tach. My Tach hasn't worked in years. I thought It was the Tach itself but thinking maybe it is wired wrong. But my question is....I believe the new DUI has an internal coil so that I don't need the old coil anymore. If that's the case what do I do with the wires that normally connect to the coil? The colors don't seem to match the wiring diagrams and don't know what is original and what may have been changed by the previous owners. I have purple wire running off the positive side of the coil to the distributor. I believe this is the power to the coil but. Not sure where the tach wire is/goes. The white wire on the positive side of the coil I believe ties into the wiring harness. I am 2 hours away from the boat. Anyways, just trying to figure out what to do with the wires on the coil. Need to find the tach wire...but then cap off the others?

I appreciate your help. I am really bad with wiring.

thanks
DanAttachment 19205Attachment 19206

It sounds like your coil is wired backwards. The pos side of the coil should have batt voltage through the ballast resistor with ign on the neg side goes to the distributor and tach. It doesn't matter now all of it will be changed. On the starter solenoid the wire on the I term should be going to the pos side or the coil it to will be eliminated. If you ever change over to a newer style gear reduction starter the wire going to the S term on the solenoid will go to the S term of the starter. Feel free to call me when you are installing I can walk you through it . Mike Hunter 678-227-8833