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Old 22-07-2013, 01:51   #1
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Is a Relay to the Starter Solenoid Needed?

The wiring chart for my 2GM20 only shows one starter switch, which is built into the instrument panel located inside the cabin. However my boat has a second starter switch in the cockpit, near the throttle. That switch is wired to a typical automotive relay, which is wired to the starter solenoid. Is this relay needed? I believe the cabin starter switch does not connect to a relay, so why would a relay be needed for the cockpit switch?

Recently the cockpit switch has been acting up. I press it and nothing happens. But if I jiggle the connections to the relay then the switch works fine. The relay uses blade connectors, which seem like a terrible idea on a boat. I'd like to either a) eliminate the relay entirely or b) replace the relay with one that uses screw terminals. Here's an example:
Solenoids & Relays | Steel & Phenolic Body Solenoids24117 | Cole Hersee - Littelfuse

That way I could crimp ring terminals to the switch wires, use heat shrink tubing and make a strong connection to the relay.
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Old 22-07-2013, 01:57   #2
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Re: Is a Relay to the Starter Solenoid Needed?

A starter solenoid takes a lot of current, so I think that a relay is a requirement. The cockpit switch (or any typical starting switch) is probably not suited for switching this amount of current, while the relay is.
Are you sure that your cabin starter switch doesn't also connect to a relay?
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Old 22-07-2013, 05:52   #3
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Re: Is a Relay to the Starter Solenoid Needed?

The standard 2GM20 starter switch does not incorporate a relay between the instrument panel switch and the solenoid but many people add one as the Yanmar loom and connectors get a little dodgy with age.

I would replace the relay as you suggested with a more robust unit (and screw terminals) and if keen, wire the cabin switch to it as well.

As you are probably aware, much boat wiring is substandard but if you use quality products and good workmanship, the final result is always good.
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Old 22-07-2013, 06:05   #4
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Typically the reason for a relay is that the wire length to the switch is longer and a relay gets around the need to use huge wire sizes. It sounds like the relay is ok but the push on connectors are loose. Try replacing the push on connectors and coating the connection with some dielectric grease. If that doesn't work then replace the relay but be sure the new relay does not require a lot more current than the old one. If it does then you may have to resize the wire to the cockpit switch.

If the cabin switch works I would not reroute it through the relay. Directly connected as it is gives you a backup in case the relay fails again.
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Old 22-07-2013, 06:14   #5
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Re: Is a Relay to the Starter Solenoid Needed?

Quote:
Originally Posted by transmitterdan View Post
........

If the cabin switch works I would not reroute it through the relay. Directly connected as it is gives you a backup in case the relay fails again.
Normally I would agree with this statement but many 2GM20 develop starting problems due to the ageing / corrosion / small wire size of the standard instrument panel loom and the simple fix is to put a relay in the circuit.
Now is a good time for the OP to future proof his starting circuit.
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Old 22-07-2013, 08:30   #6
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Re: Is a Relay to the Starter Solenoid Needed?

I had some problems, a few years ago, with starting the Yanmar 3GM30F on my boat. I discovered the problem was with the panel switch, which had become internally corroded enough to inhibit a dependable start. I have since rebuilt my entire engine instrument panel in the cockpit, and replaced the switch with a "waterproof" one (which eventually corroded inside) and replaced it with another, this time packed in the stem with grease. This switch was German and had a simple red plastic, replaceable key. Sadly, West Marine no longer carries it in their catalog.

The red ignition wire in the harness, with its 30 Amp fuse, connects to the input side of the switch. The output side of the switch connects to the input side of the start button, and the output side, the white wire of the harness, goes to the starter solenoid.
The red ignition switch wire output, in my boat, goes to a buss, from which the power to the engine instruments, etc., are connected for their electrical needs.

If anyone knows of a current supplier of these switches, I would be very happy to know. Since the key stem can be packed with grease, they can be made into very serviceable outdoor switches. Having a couple extra plastic keys is very handy. To secure the engine against unwanted use by boarders, you simply shut off the battery switch from the engine, removing power to the key switch. Any bad guy who can't figure out how to hot wire an ignition switch isn't going anywhere soon. The one who does then has to face the consequence of having entered a secured environment without permission. No details revealed here due to security restrictions.
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Old 22-07-2013, 10:58   #7
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Re: Is a Relay to the Starter Solenoid Needed?

Thank you for the terrific responses--you have given me lots of food for thought already. The engine wiring generally is a mess. There are revisions with wires that disappear and sometimes end up cut/decommissioned on the other side of a hard-to-reach bulkhead. This weekend, the ear piercing warning buzzer failed to sound (as it is supposed to) when I turned the key. So yet another little annoying electrical engine issue.

I came across a forum or blog posting recently in which another Yanmar owner had re-wired his engine from scratch, rather than replacing with the Yanmar wiring loom. Is this something to consider? I have done enough electrical work on the boat to be confident of my general electrical systems understanding and technique but the engine itself and its wiring are among a couple remaining systems on my boat where I have only a very rudimentary understanding.
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Old 23-07-2013, 01:56   #8
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Re: Is a Relay to the Starter Solenoid Needed?

Quote:
Originally Posted by erict View Post
.............

I came across a forum or blog posting recently in which another Yanmar owner had re-wired his engine from scratch, rather than replacing with the Yanmar wiring loom. Is this something to consider? I have done enough electrical work on the boat to be confident of my general electrical systems understanding and technique but the engine itself and its wiring are among a couple remaining systems on my boat where I have only a very rudimentary understanding.
The Yanmar loom is not top shelf (quality wise) and re-wiring is fairly straightforward. There are quite a few wires in the loom that aren't normally needed and if you do it yourself, just leave them out. Follow the schematic and sort what applies to your setup and only do those.

You will end up having less junctions / connectors and you will know the wiring arrangement very well by the end of the job and you could draw up your own simplified schematic for future reference.

So if you are confident of your electrical skills, I suggest you go for it
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Old 23-07-2013, 07:34   #9
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Re: Is a Relay to the Starter Solenoid Needed?

While you are rewiring, consider adding an oil pressure sensor (it feeds a gauge, not an idiot light) and a water temp sensor (also feeds a gauge). These are easy to do and provide you with actual information of what is developing in the engine, rather than that sudden discovery that something just happened. I kept the "idiot lights" and installed them, with different sounding piezoelectric buzzers, above their representative gauges. That way, when (not if) something happens, you will be alerted and be able to quickly confirm the issue.
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Old 28-07-2013, 02:06   #10
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Re: Is a Relay to the Starter Solenoid Needed?

I am finding that good quality switches are getting hard to find, this applies particularly to bilge pump float switches.

Also I notice that a lot of the supposedly marine rated electrical equipment now comes with un-tinned wiring.

Having both pressure and temperature transducers and switches and analog readouts and warning lights and sounds is a good idea.
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