Why a stop solenoid?

Was amazed to see our GB42C from 1986 has a on/off engine stop solenoid switch on the panel.

Apart from the initial bewilderment at not being able turn off an engine until I discovered this switch, I was wondering why would this option be provided in the first place?

Kindly explain how you expected to stop the engine.

Most diesel boats have a key to turn on the ignition, then a start and stop switch to do just that. My Formula has a key like a gas boat or car to start or stop.

Some have just a key...same wiring, just all the energizing thru a key switch.

Especially those that have a fuel solenoid that need power all the time to stay open like a Cat 3208.

There are two types of start/stop solenoids depending on the engine. Yanmar and Volvos (I think) have engage to stop solenoids. You have to send a signal to the solenoid to stop the engine. The engine will continue running even with loss of all power at least for older mechanically injected engines.

Cummins and Cats use an engage to start solenoid. Unless there is a signal going to the solenoid the fuel stays off and the engine won't start. Loss of power immediately kills the engine.

There are pros and cons for each type.

David

DavidM said:

There are two types of start/stop solenoids depending on the engine. Yanmar and Volvos (I think) have engage to stop solenoids. You have to send a signal to the solenoid to stop the engine. The engine will continue running even with loss of all power at least for older mechanically injected engines.

Cummins and Cats use an engage to start solenoid. Unless there is a signal going to the solenoid the fuel stays off and the engine won't start. Loss of power immediately kills the engine.

There are pros and cons for each type.

David

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My Perkins 4.236 has a "STOP" solenoid. Well.....actually it was a pull-cable for years. I only recently installed the OEM stop solenoid.

For simplicity, I like the STOP solenoid. Downside is it certainly makes the boat easy to hot-wire: just jump across the starter solenoid.

Peter

My diesel has an ignition key and a stop button. The key alone will start and stop the engine, but the manual says to use the stop button and then turn off the ignition. I haven't investigated it yet, my guess is the ignition switch turns off the fuel pump and injectors and the button operates a kill solenoid to stop the fuel. I use the button since that's what's recommended, but I haven't found it makes a difference if I don't.

If you gave not done so already, it is a good idea to find the stop solenoid on the engine in case you ever need to operate it manually in case an electrical connection fails. You want to know where everything is on the engine anyway, but this is a good one to prioritize, easier to look around a cool and quiet engine than that is one hot and noisy.

Gdavid said:

If you gave not done so already, it is a good idea to find the stop solenoid on the engine in case you ever need to operate it manually in case an electrical connection fails. You want to know where everything is on the engine anyway, but this is a good one to prioritize, easier to look around a cool and quiet engine than that is one hot and noisy.

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Thanks and I agree. Maybe this season. Also, you can always manually close the fuel line valve. I have one mounted on a bulkhead next to the Racor. I think that would be easiest to reach in an emergency.

Soo-Valley said:

Kindly explain how you expected to stop the engine.

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Gut-wrenching laugh at your comment.

DavidM said:

There are two types of start/stop solenoids depending on the engine. Yanmar and Volvos (I think) have engage to stop solenoids. You have to send a signal to the solenoid to stop the engine. The engine will continue running even with loss of all power at least for older mechanically injected engines.

Cummins and Cats use an engage to start solenoid. Unless there is a signal going to the solenoid the fuel stays off and the engine won't start. Loss of power immediately kills the engine.

There are pros and cons for each type.

David

Click to expand...

My Yanmar 6LPA-STP 315 HP engine must have the power panel circuit breaker on to start with a rocker switch at the helm. If I flip the CB off, the engine shuts down. So, engaged to run. The lower side of the rocker switch shuts the engine down even though the poer panel CB is still on.

On the topic of stop solenoids, I had a very perplexing problem: an engine that would, when the ignition switch was first turned on, pass the power on self test, but not allow the gears to be selected and would not allow the engine to turn over with the start button pushed (the computer won't let the engine turn over without a gear control station being selected and in neutral, so I didn't know whether the problem was with the engine electronics or gear electronics). It turns out that the momentary switch that activates the stop function (not a solenoid per se, but a signal to the engines ECU) had failed in the circuit open position (this was a normally closed momentary switch, so the failure was as if the stop button was pushed when it wasn't. I know this is a little off topic, but since I was perplexed for months until I finally tracked it down, I thought it worth sharing.

Bongi said:

Was amazed to see our GB42C from 1986 has a on/off engine stop solenoid switch on the panel.

Apart from the initial bewilderment at not being able turn off an engine until I discovered this switch, I was wondering why would this option be provided in the first place?

Click to expand...

The boat I have now is my first diesel engine. The boat was put on the travel lift and in the water and I started the engine. My two friends and I went on a 10 mile trip to my slip. We got there, tied the boat up and moved the key to the OFF position. Well, the engine kept on running and I am hitting the STOP button. My friend has a big smile on his face and said, turn the key to on and than hit the STOP button. OOOOOOOOHHHHHHHHHH!!!

I though about it, and no ignition system so the fuel needs to be cut off.

Here's a diesel ignition switch wiring diagram with a stop position....

Most older sailboats and other smaller craft have a cable you pull to shut down. Perhaps that's what the OP is used to. That wouldn't work too well on a large boat with maybe two helms so they put in stop solenoids. I you're used to a diesel in a car or light truck, they almost always have an "energize to run" solenoid that stops the engine when you turn the key off. Acts like a gasoline engine. And correct, you need to know where that solenoid is and how to engage it manually. The old Detroits in one of the tour boats I ran has "energize to stop' solenoids and they sometimes hang up and won't shut down. You then have to go down to the ER and push the plunger manually. I suppose in an emergency you could do the same with "energize to run" solenoids, and hold them closed with a zip tie or something to get you home.

Soo-Valley said:

Kindly explain how you expected to stop the engine.

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I was wondering how oil changes were done. And, doesnt all the noise and shaking get old?

I love this forum, the opinions are delight to read! I have recently transitioned from a Californian which also had Cat 3208s, but with a key to energize at first position and then at next position would start the engine.

On our GB42 we also have a engine power on switch, which when turned on sounds the buzzer and energizes the start button. Pressing that starts the engine.

I guess my question stems from why wouldn’t GB simply energize the fuel solenoid when that engine on switch is turned on. That way it energizes everything and simply to press a start button to start….. pressing the off button could then isolate the fuel solenoid for as long as it is pressed and the engine will shut down. Releasing it leaves the engine energized and buzzer buzzing, but engine shutdown.

So to the question ‘How do I propose shutting the engine down?’… that is how I would envisage it, but it seems GB had another purpose to arrange it this way… possibly it added safety?

I’m not planning to change anything in the setup, but was curious why they chose to separate the fuel solenoid in this way.

I'm sure a real marine mechanic will check in. But here's my take on it. Many if not most marine engines pre electronic controls are either energize to shut down or manual shutdown. Like your current boat. Cat 3208s can be setup either way, energize to run like a car or truck engine the usual setup.

There are advantages and disadvantages to both systems.

Energize to shutdown or manual shutdown requires no electrical power once the engine is running. But it's harder to protect the engine against faults or to properly activate an automatic fire system.

Energize to run requires electrical power to keep running. But it's easy to interrupt that power to provide fault protection or shut the engine down on automatic fire system activation. Energize to run introduces more potential failures.

I think prior to all the other replies you need the understanding that diesel engines do not have an ignition, so turning off the "ignition key" will do nothing at all, unless other provisions are made. The key typically operated the starter solenoid, and may also control a valve to the fuel supply.

A mechanical diesel has neither throttle, nor ignition and will run until either the fuel supply or the air supply is cut. A common rail diesel will run until the power to the injectors and ECU is cut off.

Portage_Bay said:

I'm sure a real marine mechanic will check in. But here's my take on it. Many if not most marine engines pre electronic controls are either energize to shut down or manual shutdown. Like your current boat. Cat 3208s can be setup either way, energize to run like a car or truck engine the usual setup.

There are advantages and disadvantages to both systems.

Energize to shutdown or manual shutdown requires no electrical power once the engine is running. But it's harder to protect the engine against faults or to properly activate an automatic fire system.

Energize to run requires electrical power to keep running. But it's easy to interrupt that power to provide fault protection or shut the engine down on automatic fire system activation. Energize to run introduces more potential failures.

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"Energize to run" not only used electricity, but the solenoid can get hot and it wears out faster as it's engaged the whole time the engine is running. "Energize to stop" is only engaged for the few seconds it takes to shut down. Almost no electricity used and much more reliable. But not as convenient. All the commercial boats I've run had push to stop buttons.

Ah… that may be it JGWinks. Which suggests the Californian arrangement may accept the tradeoff of the current draw risk for the convenience of having a key ignition not unlike a car.

Thanks to all for the insights.

Bongi said:

Ah… that may be it JGWinks. Which suggests the Californian arrangement may accept the tradeoff of the current draw risk for the convenience of having a key ignition not unlike a car.

Thanks to all for the insights.

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I don't think it was a tradeoff by Californian. Other boat manufacturers installed 3208s with energize to run. I think it has more to do with the engines. 3208's are truck engines and that was the way they were built. I've looked into changing to energize to stop but have decided it's not worth the effort. Studying the wiring diagram it appears to be more than simply changing out the solenoid.

While jgwinks has a valid point about risk of the solenoid wearing out I don't think on a typical recreational boat it is much to worry about. A work boat will put more hours on their engine in two or three weeks than the typical cruiser will in a full season. Running 24x7 for a week is 168 hrs. My boat came to me with 1983 vintage 3208s the solenoids appear to be OEM and are still working fine. It's easy to carry a spare and on 3208s they also usually are powered via relay so a spare of that also.

Not saying anybody would actually wear them out, but that's the way they used to do it all the time. The ones on the tour boat that hang up are from 1964 and no idea many hours, there aren't any hour meters. They work most of the time, just need a shot of lube now and then.

Gosh, in the scheme of things, i gotta believe a solenoid is relatively reliable. A coil of wire with a plunger in the center. Almost all production car truck and marine engines use solenoids on every cylinder.

diver dave said:

Gosh, in the scheme of things, i gotta believe a solenoid is relatively reliable. A coil of wire with a plunger in the center. Almost all production car truck and marine engines use solenoids on every cylinder.

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Agree....

The "power on" fuel managing solenoid on my Westerbeke Genny in my last boat had one coil (powerful) to pull the lever to the correct position, then a smaller coil to hold it in place (engineered to need less pull).

They last thousands and thousands of hours and are designed to work for days on end. Mine looked original with something like 5600 hours on it.

psneeld said:

Agree....

The "power on" fuel managing solenoid on my Westerbeke Genny in my last boat had one coil (powerful) to pull the lever to the correct position, then a smaller coil to hold it in place (engineered to need less pull).

They last thousands and thousands of hours and are designed to work for days on end. Mine looked original with something like 5600 hours on it.

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Solenoids are very reliable. The boat I regularly worked on pre-retirement had a pair of gennys with over 20,000 hrs each, energize to run, never a hint of a problem with the solenoids.

I think there are pluses and minuses to both. Energize to run has the benefit that if it fails it stops but if the electrical system fails it's also stops. The energize to stop will keep running even if the electrical fails. But if the solenoid fails it won't shut down. I have pulled the wire off my solenoid to shut down my engine and it was a good thing.

Doodie99 said:

I think there are pluses and minuses to both. Energize to run has the benefit that if it fails it stops but if the electrical system fails it's also stops. The energize to stop will keep running even if the electrical fails. But if the solenoid fails it won't shut down. I have pulled the wire off my solenoid to shut down my engine and I is a good thing.

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I would prefer the latter. You can shut off the fuel manually if you lost power. In the case of an emergency where you lost power for some reason, I'd rather have an engine that wouldn't stop than one that wouldn't run.

Soo-Valley said:

Kindly explain how you expected to stop the engine.

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This is still my favorite response!

Soo-Valley said:

Kindly explain how you expected to stop the engine.

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Simple, you leave a dock line hanging overboard and shift into gear. Retrieving it is the hard part.