Detroit Diesel Starter set-up

My Bertram 38ft flush deck cruiser was powered with 8V 53 naturals with a single starter solenoid on the 12 VDC starter.

Never has any trouble starting, although there was a paralleling switch which boosted the starting amps.

You will just need to get an ignition switch that is rated for the proper amperage and a heavier wire to the solenoid. You use two solenoids to make up for voltage drop. A picture would help. It may be a solenoid to parallel the batteries.

The heavy current that the starter solenoid requires can not be supplied easily from the ER, to the helm, back to the ER and starter.
A lighter current drawing solenoid is used to supply short run, high current & voltage to the starter while getting it's lower current signal from the helm.

You need to leave it as designed and installed.

Surely the wires to the helm are only carrying the control voltage and a low current necessary to energize the coil which closes the contacts in the solenoid not the full voltage and current required to turn the engine.

The heavy current that the starter solenoid requires; not the starter motor.

wires to the helm are only carrying the control voltage and a low current necessary to energize the coil;
Energize the OPs first coil (solenoid), close it's contacts between the battery and the starter solenoid. That then provides the starter solenoid with all the current it needs to engage the pinion and hold it's own heavy contacts closed for the starter motor.

Like a wired remote control. Just lighter wires and heat at the helm.

If there was any confusion, I hope that clarifys my previous text.

Still; I recomend to leave it as designed and installed.

The solenoid only requires the amount of current to energize the coil and pull the magnet. It is nowhere near the current the starter itself requires. That passes thru the contacts not the coil itself.

Look at your genset or car with a pre engaged starter, there will be a little tiny wire between the two terminals on the solenoid, this is connected to your ignition and will not carry anywhere near the current the starter requires but seems to work just fine doesn't it?

No
The Detroit starter solenoid draws big current. It swings and holds the pinion in place also holding the rather large contacts down turning on the starter.
There is a rather large return spring the coil pulls against also.
Detroit starters do not use an auto engage / disengage pinion as on a newer small car.
Remember the OLD Chevy starters?

All the DD's I have seen use a pre engage type starter.

You should really spend a bit of time when you have some spare time and work out how one actually works as you are obviously confused at to which bits do what

This typical DD starter has a solenoid on it to engage the pinion and make the electrical connect to the motor.
This solenoid winding /coil will draw current to over come a return spring, hold the pinion in place and hold the internal contacts down while it starts it's engine.

Rather than trying to do, whatever you are doing, Would you care to contribute to the thread and let the OP determine what the best answer for him is?
What are your thoughts on keeping the extra solenoid?

The starter shown is a pre engaged type starter, the picture looks very much like one on Amazon.

You have described how a solenoid works. The solenoid contacts carry a large current which is the load caused by the starter, the solenoid itself ( the windings that form the electromagnet) carry very little in comparison.

There is no reason that that starter can not be run with an extra solenoid working as a relay to limit the current in the switch wires or run directly from the switch if the cable is sized to suit the load.

In case you missed it, this is the point I have been trying to get across since my first post on this subject.

On a 12Vdc system, it does draw some current (I do not know the numbers in Amps). This is probably why there is already a factory installed second solenoid.

I could not tell.

Why are you trying to re-invent the wheel. What you have is what Detroit Diesel felt was necessary, it works and is a reliable setup, so why change it?

I would not say the OP is trying to re invent the wheel. He/She might well just want to tidy up and modernise the installation. This is something that is relatively easy to achieve if you understand what the components do and take this into consideration in your planning.

It's pretty tidy now. The 2 solenoids are mounted right on the motor in an area that is not a problem. What the OP is doing is searching for a solution to a problem that in this case does not exist.

Are you familiar with the actual vessel the OP has? It might have left the factory like that but by now it could have had any number of sticky fingers fooling with it.

Kinda late into this, but without wiring diagram or photos, I would say if it ain't broke, don't fix it.

Leave it alone. By the time the voltage makes it to the helm, through the switch and back to the solenoid there is a voltage drop. It may work for a time, but if you have anything less than a fully charged battery, you WILL get failure to start due to insufficient voltage to pull that big solenoid in. You can maybe get around that by using a ridiculously heavy wire from the battery to the switch and back but why?

No, I'm familiar with the factory D.D. starter wiring setup which he described that he has, mounted on the motor.