Topic: 1957 RD-18 30HP Electric start install – Antique Outboard Motor Club,Inc

This topic has 30 replies, 5 voices, and was last updated 2 years, 4 months ago by Gary Pasquale.

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December 12, 2022 at 1:22 pm #269929
Gary Pasquale
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I have a 1956 RD-18 that I am adding electric start,

Items accumulated so far are:

Flywheel of a 57 35hp

Starter and correct bracket

Bottom half of carb from a 57 where the choke can sit

e Choke

solenoid (not sure where I am going to mount just yet)

I do NOT intend on adding a 12v generator.

Now for the question: Wiring harness

I have made a few harnesses in my time so I am familiar with what and how the mechanics work but I have never made one for a motor this old.

This is whatI have used in the past

This is what I have found for a 57 35HP

Any good reason why I should not use the simpler wire harness (73-76)
- This topic was modified 2 years, 4 months ago by Gary Pasquale. Reason: didn't finish, hit submit to soon
- This topic was modified 2 years, 4 months ago by Gary Pasquale.
December 13, 2022 at 11:19 am #269964
Phil Budne
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I hope FrankR will chime in, since I’ve never wired a “big twin”, only an 18-hp (without cut-out or safety switches), like your first diagram (but with the start solenoid in a box, rather than under the hood).

My understanding is that there are a number of variables, and man diagrams that cover some (but perhaps not ALL) the combinations of elements you might put together.

Are you planning on a 6 or 12-volt system?
My understanding is that you can run a 6V starter on 12V, but 12V will burn out a 6V choke solenoid.
You can add a ballast resistor and use a 6V choke solenoid in a 12V system.

Using a key switch or a start button?
Your first diagram shows a key switch with stop (kill) wires going back to the magneto plate.
Earlier big twins didn’t have a kill switch, but you can add it, by drilling holes in the magneto plate (quick disconnect connectors are a big plus here, or it will be hard to take off the magneto plate!)

Here’s a past post with diagrams that may be helpful:
https://www.aomci.org/forums/topic/1955-evinrude-big-twin-electric-diagrams/

http://www.omc-boats.org
http://www.aerocraft-boats.org
December 16, 2022 at 2:45 am #270017
billy-j
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You have the bottom of an electric start carburetor but I also think some of the electric start throttle linkage is different from a manual start linkage.
December 16, 2022 at 8:52 am #270019
Gary Pasquale
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I actually have the entire carb from a 57 35hp
December 17, 2022 at 5:06 pm #270066
fleetwin
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Your first diagram is for a later model with the beloved “low tension” ignition, this set up won’t work on your engine. The second diagram is for a 57 35hp with electric start and generator, so a little over complicated for your engine.

The decision you have to make is whether or not you want to be able to shut the engine off using the key switch. If so, this will add complexity to the set up that isn’t desirable. Your manual start engine does have the vacuum switch/cut out system for the ignition which helps with lean deceleration/lean over revving. Trying to adapt, wire this into a stop circuit controlled by the key switch, will be tricky. Flimsy leads and chafing could lead to inadvertent engine shut off.

I would recommend just using a simple set up that has a lead for the electric choke, and forget about trying to wire in a “stop circuit” at the key switch. The engine can always be stopped by pulling the remote control throttle lever all the way back or activating the electric choke.

I’m not sure I understand your questions about wiring the electric choke, just be sure it is a 12v choke solenoid. I do know that these air boxes, electric start brackets and electric choke mounts changed during those few years, so it may be tough to find the correct electric starter bracket.
December 18, 2022 at 5:20 pm #270093
Gary Pasquale
Participant
I do wish to have the motor cut out with a key, why can’t I just add 2 leads (1 to each set of contacts) and wire it to the key (acting as a cut off switch). I don’t see this interfering with the existing vacuum switch/cut out system. At some point in the future I will have to add a cut off switch per law.

TYVM in advance 🙂
December 19, 2022 at 7:49 am #270100
Gary Pasquale
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After doing some more research, I should be able to do the following. From the ignition run a line to the center post of the vacuum switch, and an additional line from the ignition to the upper cylinder set of points.
December 19, 2022 at 8:35 am #270101
fleetwin
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US Member
It’s up to you for sure. Does your engine currently have a stop switch mounted on the engine’s lower pan? If so, it will make the stop/key switch wiring a little easier. Otherwise, you will have to add two more leads/stop leads to the mag plate, which means removing the mag plate so you can add the additional wire(s) and clamp them underneath properly.
December 19, 2022 at 2:53 pm #270108
Gary Pasquale
Participant
I quickly put this together for comments.
- This reply was modified 2 years, 4 months ago by Gary Pasquale. Reason: updated image
December 19, 2022 at 2:55 pm #270110
Gary Pasquale
Participant
Motor is getting a total rebuild, so removing the mag plate is a given. 🙂
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