Electrical for running engine on stand

R

rdwyer

Member
Joined
Nov 3, 2010
RO Number
32383
Messages
5
Hi all.

I have some questions on electrical needed to run my 1998 Vortec 5.7l engine on a stand (my engine will be bolted to wood base made from 6X6 pressure treated posts).

So far I have:

Positive battery to starter main post
Negative battery to engine block
Momentary push button switch from positive terminal to solenoid terminal

Questions:

I know I need to power the positive side of the coil…don't I need some sort of resistor between the positive battery terminal to the plus side of the coil? (plus side currently has 1 purple to it and two grey wires to the negative)

In order to read the water temps and oil pressure using the electrical gauges I have, where else do I need to provide power?

The coil is a HEI Ignition Coil MerCruiser Thunderbolt IV & V Replaces 392-7803A4 & 392-805570A2.

The ignition system is a thunderbolt 5
 
The TB ignition system uses 12v at the coil so you don't need a resistor.. Do you have a keyed ignition or just straight wires?

Don't connect the batt to the coil(+) as that completes the ignition circuit. You connect when you want to run the engine. As far as the starter, do you have both solenoids connected? If so, all you should have to do is connect the two small connections of the slave solenoid. Best to sut in a little push button switch for this as it's a temporary (intermittent) connection as in the starter switch. You can test the starter here without connecting the coil which just rotates the engine. and a good thing to test. It's the same as a remote starter.

If the starter turns the engine over without smoking wires, you're ready to connect the coil and run the engine. Don't forget the water flow.
 
Do you have the mercruiser harness ( I think it’s 10 pin) on the motor? I bought the ‘male’ end, found a diagram and hooked up an ignition switch to it - that powered everything. I also connected oil pres and temp gauges to the harness I built.
 
Thanks to both for responding.

So I would power the coil with a toggle switch just before starting which I assume is the equivilent of the key in the "on" position. I have a momentary plunger switch I've used to turn the engines over for a compression test in the past so no problems there.

That just leaves getting electric to and from my water temp sensor and my oil pressure sensor. I've got both electrical gauges so I don't want to buy a mechanical oil pressure gauge.

Alk, I do have that 10 pin electrical connector bolted to the engine now. Suppose if I find an electrical diagram for the NON engine side of it I could hook things up from there....it's just that it's pretty simple to do using the approach above...only reason I'm considering the pin method is to get my guages working.
 
Yes, you can easily find the diagram for the mercruiser 10 prong plug via google search. Easiest way to power and hook up,the gauges, no doubt. I bought the male plug , to build my harness, but I suppose almost as easy to jump the harness directly.
 
Just looked at he diagram and the wires from the sender go directly back to the respective gauge given that i will just run a wire for each to the gauge.
 
Thinking about it, buy a simple ignition switch. Mount it on a piece of plywood attached to your engine stand. Run a 12ga red wire from the Batt(+) to the Batt connection on the switch. Connect the Pos (+) side of the coil (the one that doesn't go to the distributor) to the IGN connector of the switch. Run a wire from the Starter (ST) connector on the switch to one or the other connector of the solenoid. Gotta test which one activates it when the switch is turned to the start position.
 
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