Wiring for HEI and single terminal Altenator

[nubble94]

I took the only wiring diagram that I have found and redrew it to what "I think" (LOL) how an HEI distributor and a single terminal alternator should be wired in a boat. Since I am a newbie to boats, I am asking for any suggestions. Tks..Tom

[Fire Water]

Tom. I would suggest using a relay instead of running straight from the ignition switch to your distributor. Use a min. 14 gauge (I use 10) wire from the positive lug on your starter through the relay contacts and then into the distributor. Use your violet wire to control the relay. It will need to be a continiuos duty normally open relay. HEI ignitions need good clean supply of power. You may also want to add some performance parts to your distributor or replace it with a billet style. Stock HEI systems start to drop sparks around 4500 RPM.

[Jetaholic]

I'll second the relay on the distributor. This will minimize the amount of current that actually flows through the ignition switch itself. I'm sure a relay coil has much less current draw than the HEI coil does.

[nubble94]

I believe that a relay would draw as much current as the coil. Coils produce voltage level and "discharge current". It just sounds like something more that can quit working at the wrong time.

[Jetaholic]

I believe that a relay would draw as much current as the coil. Coils produce voltage level and "discharge current". It just sounds like something more that can quit working at the wrong time.
Actually no. In order to generate as much voltage as it does at the secondary with very little current, at a 12 volts input on the primary you would have to have quite a bit of current on the primary. Your coil is basically a big "step up" transformer. The input voltage is low and the input current is high, however the output voltage is high and the output current is low. If you were to plug in the input current and input voltage into this equation:
P=IxE where:
P=Power (Watts)
I=Current (Amps)
E=Electromotive Force (Voltage)
you would end up with how much power is being consumed at the input. On top of this, do the same with the output voltage/current with this equation. You will find that the input and output power are pretty close to the same value, depending on the efficiency of the transformer (no transformer exists that has a 100% power transfer efficiency).
A relay coil in the range of 300-400 ohms across a 12 volt source would only draw about 30-40mA of current from the source...far less than what your ignition coil would draw.
As far as discharge current, if I'm correct you're thinking of the counter voltage that is induced when the magnetic field collapses around the coil. Well, with a constant voltage flow through a relay coil, you would not have that counter voltage, so there would be no discharge current until power is cut off to the relay.
Just my $0.02.

[nubble94]

Good info. Thats why I asked. Got a suggestion for a relay, something that will survive the enviroment.

[DUCKY]

Use a Bosch 20/30 relay. It or something comparable should be available at any parts house for $5-7. They are generally trouble free, but not a bad idea to carry one in your tool box. It will have numbers on it to identify the terminals. #30 will be your high current input (12 or 14ga direct from battery, via circuit breaker) #87 will be your output to the distributor (12 or 14ga), #87a will be un-used, #85 will be ground (16ga), and #86 will be the lead from the ign switch (16ga). I prefer to buy just the relay by itself and wire it using marine standard colors, but you can also buy the ones with the pre-wired harness plug for a little more money.

[wet77]

I have been running a relay on my msd HEI and it works great!

[nubble94]

I redrew the schematic to reflect a relay to the HEI distributor.

[Fire Water]

That looks pretty good. I would suggest using a fuse or circuit breaker (as Ducky said). Mine is a thirty amp, sounds pretty high but I run a hot ignition system. I'm not trying to protect the components just avoid an electrical fire.
One other thing you might consider is this. If you are going to be running your engine at high speed for extended periods of time it is possible to overcharge the battery. I run an undersize pully, this keeps me from overcharging and I get back some horsepower.

[nubble94]

Firewater
Do you mean a fuse in the feed from the Battery to the HEI?

[Fire Water]

Yep, that's right. Close to the battery terninal so your protecting as much of the wire as possible.

[Wicked Performance Boats]

I have always run the one wire alt directly to the Battery terminal on the sol. Why do you need a relay? It sounds to me like another part to go bad. You do not need to route it thru the ign sw. BL

[Fire Water]

Wicked, We were talking about two different things. Nubble was asking about the hot wire Feeding the HEI.

[Wicked Performance Boats]

Wicked, We were talking about two different things. Nubble was asking about the hot wire Feeding the HEI.
FW, Sorry I got confused. BL

[Fire Water]

No Problem. Got the e-mail on the motor mounts and oil cooler. Thanks

[wanabe]

I just ran across this thread because I'm rewiring a boat (first time); I have diagram very similar to this BUT this diagram shows the feed to the Distributor from the 'Bat' terminal of the Solenoid; my diagram runs to the Distributor from the 'R' terminal of the Solenoid.
Which should it be?

[hotrod56cars]

I just ran across this thread because I'm rewiring a boat (first time); I have diagram very similar to this BUT this diagram shows the feed to the Distributor from the 'Bat' terminal of the Solenoid; my diagram runs to the Distributor from the 'R' terminal of the Solenoid.
Which should it be?
If your run it to the BAT terminal your engine will never shut off irregardless of key switch position.

[wanabe]

If your run it to the BAT terminal your engine will never shut off irregardless of key switch position.
Then this revised diagram is incorrect; I have it run correctly from Solenoid 'R' to the Distributor.

[Oldsquirt]

Wanabe, the "R" terminal on the starter solenoid is only used during cranking and only on points type ignitions. It bypasses the ballast resistor which you find in a points-type ignition. It is inactive while running. If you use it to supply power to your ignition, you will have spark while cranking, but the ignition will shut off as soon as you release the key to the "run" position.
Post the diagram you are speaking of.