4b - Mercruiser Thunderbolt?- OLD VIDEO - Read Description

In this video I’m improving on the wiring of the Delco EST ignition system and correcting a mistake that I made in part 1. Examine the wiring diagram found here;

https://www.justanswer.com/boat/53kfn...

Note that the purple wire serves three loads, the ignition module, the ignition coil, and the fuel pump. It also serves an electric choke if you have one and it goes to the back of the alternator although I don’t think that’s a load.

I think that’s too many loads for the purple wire to handle especially since the new Delco EST ignition coil has a 14 gauge wire and the purple wire is at most a 16 gauge wire. So I decided to install a relay and provide the ignition system with a higher amperage supply almost directly from the 50 amp circuit breaker. I installed a relay switched by the purple wire but taking power from the hot side of the auxiliary starter solenoid.

In the second half of this video I replaced the temperature sensor for the over temperature warning system with a temperature switch. The part number of the switch is Mercruiser 48952 and it costs $95. I was mistaken about the tan/ blue wire and coolant wires in Part 1 of this series. These wires are not passed through. The temperature device is actually a thermistor sensor that provides a temperature signal to the TB V module and there is logic in the module that grounds the tan/blue wire to turn on the high temperature alarm. So if you connect the tan/blue and yellow wires as I did then you need to replace thermistor sensor with a temperature switch as shown in the latter part of this video.

If you are savy with wiring and understand what I’ve done in this series you can leave the Thunderbolt module in place to keep the high temperature alarm function but then you’ll have two modules and a messy installation. The way I’ve presented the upgrade in this series is a cleaner better way to do it in my opinion but it will cost an additional $100.

Update 2/7/2022 - In the link below I may have found a cheaper source for the over temperature alarm switch. I have not used the switch in this kit so buyer beware but for the price it’s worth the gamble.

https://www.nautiqueparts.com/product...

If this parts works for you report back here so others can learn about it.