View Full Version : MOB alarm

ron ll
04-24-2007, 10:47 AM
In another thread, "Concordia" mentioned the Life Tag system http://www.raymarine.com/raymarine/default.asp?site=1&section=2&page=1344

I often single-hand "Snoose", a 37' converted salmon troller, and usually with the autopilot engaged. Which means if I fall overboard, about all I could do is wave goodbye. It burns about 1 gal/hour and carries nearly 300 gallons. It aint gonna run out o' gas while I'm watching.

The Life Tag simply sounds an alarm. However it seems to me it could also be rigged to perform some kind of electronic switching. Problem for me is my Detroit Diesel 3-71 has no electronics to shut down. The only way to stop the engine is by pulling (hard) on a cable for several seconds shutting off the fuel. So I'm thinking I would have to rig the Life Tag to trigger the Autopilot to hard-over so the boat at least comes back to me, if only to run me over at 7 knots. :(

Any better ideas?

Bruce Hooke
04-24-2007, 11:02 AM
Idea number 1: wear a harness and clip yourself in when you are underway.

Idea number 2: how hard would it be to rig an electronic fuel shutoff?

04-24-2007, 11:18 AM
If you attached your life tag to the cable, when you fell overboard it would pull hard enough to kill your engine.... Of course, it would also restrict your mobility somewhat... ;)

ron ll
04-24-2007, 11:22 AM
A harness would be a very prudent practice. But as rational as it is, it probably isn't going to happen in real life. (Yeah, I know, what good is real life if you don't have one?)

An electronic fuel shutoff might be good, or at least better than a hard-over on the autopilot. Can a fuel shutoff simply be installed in the supply line? Keep in mind this engine supplies ten times the fuel consumed and returns 90% to the tank, but I guess that shouldn't matter.

Bruce Hooke
04-24-2007, 11:31 AM
I can't see what good it would do to have the boat circling at speed, except maybe to attract attention. If there is one thing worse than seeing the boat disappear into the distance it would be seeing it coming right at you at full throttle!

I am not a diesel mechanic by any stretch of the imagination so I have no idea what sort of fuel shutoff you could install. I simply asked the question since it seemed like the obvious one to ask.

It does not seem like it would be TOO difficult to set up some sort of motor that would yank on the fuel shutoff cable.

You could also look at ways to control the throttle.

You might want to at least try getting a harness and clipping in. Once you get in the habit it really is not that much of a nuisance. I don't like the idea of trusting my life to a bunch of electronics that are supposed to shut off the engine if I fall overboard.

S.V. Airlie
04-24-2007, 11:36 AM
I agree on the harness.. You do get used to it and attaching it becomes second nature.
I'm still trying to figure out how this shut off would work. I mean, if you attach a line to it.. from what I am seeing, and attach that line to yourself.. as there ain't anyone on the boat to yank it, is it much different than attaching a harness to the boat and you?

What am I missing here?

Bruce Hooke
04-24-2007, 11:43 AM
Leaving aside what Lefty said, I think the idea is to have the Life Tag system (which apparently triggers some sort of alarm if you fall overboard) instead trigger some sort of fuel shutoff...

S.V. Airlie
04-24-2007, 11:53 AM
I looked at the unit... being wireless, I suppose some mechanism could be designed that would take a signal to a shut off valve but it seems more complicated and expensive than it is worth. just my opinion.
Umm.. I'm also wondering whether this system works at night.. as it seems to rely on movement.
For some reason, I often find myself sailing at night. As Chuck says.. a puff boat has no ETA, just a destination..

04-24-2007, 12:08 PM
Ocean Voyager 2007 (the annual issue of Ocean Navigator) reviews MOB systems and several have engine shutoffs. Some sites to check out...

Mobilarm (http://www.mobilert.com)

Emerald Marine (http://www.alert2.com)

Mobwatcher (http://www.mobwatcher.com)

ron ll
04-24-2007, 12:25 PM
I 'think' the Life Tag probably works on an ir signal which goes away when it gets too far from the receiver unit. As the receiver unit already triggers an alarm, I was thinking just convert that to some shutoff device. But I agree, all somewhat complex and prone to leaving you dead. Even if it shut off the fuel, by the time the engine shut down and the 28,000 lb boat came to a stop, thats a whole lotta swimming in real cold water.

The harness is probably the most logical; (I guess being dragged indefinitely thru the water at 7 knots is better than nothing). So it comes down to a long life on a leash, or a somewhat shorter life of freedom. As I've already somewhat recklessly made it to 63, I might have to think about that. :D

S.V. Airlie
04-24-2007, 12:30 PM
ron.. Look at the bright side.. Ya got a trawler.. No having to go forward to bring down sails etc... at 2am...
That's why I um use a harness.:D

04-24-2007, 12:48 PM
exactly how many pounds pull is required of the shutoff cable, and how far must it be pulled......?
a simple ledex type rotary motor, non reversing could be rigged with a latching relay. Loss of signal would take the alarm sensor voltage, trigger the device, it would latch the "STOP" cable into a full present pull mode and stop the engine. At the same time you could close an air vent to shut off the air supply. To release the mechanism a simple push button switch would be required. The stop motor could also lock the helm hard over to reduce drift.

Gary E
04-24-2007, 01:29 PM
Your Detroit Diesel doesent have a Stop Solenoid ?
Get one

ron ll
04-24-2007, 02:18 PM
No it doesn't have a stop solenoid. Please tell me more.

Gary E
04-24-2007, 02:26 PM
The modern DD... modern being newer than 30 or 40 years old all have or should have a STOP Solenoid to pull the Rack closed and that shuts off the fuel from the injectors and that stops the engine. Sugest you visit any DD repair shop or any owner of a Sportfishing boat and have a look. the idea is sooo simple...

Maybe the SS pulls the same place that the wire does that you pull now..
The only manual pull I know about is the EMERGENCY STOP that covers the Blower Intake...Pull that and you shut off tha AIR... and usually then you need a rebuild on the Blower because the seals are shot

04-24-2007, 02:36 PM
If you rigged jackline(s) on deck that your harness clipped to and a line from the jackline to the fuel cutoff you may be able drag astern and shut off the engine just by your weight on the harness should you be unconscious. It would take some fiddling to work out. Sailors who use autopilots (wind driven or electronic) should have something similar so their boats would round up to the wind.

ron ll
04-24-2007, 02:42 PM
(Gary E)
Nope, mine is circa 1952 and does not have that. The cable pulls a lever on top of (the throttle box?) which shuts off the fuel. I'll check with my mechanic, but I'm kind of doubting it can be retro-fit on this rack assembly. But thanks for the heads-up on that.

Gary E
04-24-2007, 02:42 PM
You might find ths interesting



Gary E
04-24-2007, 02:44 PM
Nope, mine is circa 1952 and does not have that. The cable pulls a lever on top of (the throttle box?) which shuts off the fuel. I'll check with my mechanic, but I'm kind of doubting it can be retro-fit on this rack assembly. But thanks for the heads-up on that.

Chances are you could rig a solenoid to do what the Pull Wire does now.

Gary E
04-24-2007, 03:12 PM
This falling over the side seems to be of concern to many of you...
Have ANY of you fallen over?
Do ANY of you KNOW of ANYONE who did?

I know of one... and that's in over 40 yrs of being around sportfishing boats.

Bruce Hooke
04-24-2007, 04:08 PM
I certainly know of fisherman who have been pulled over the side (it happens all too often), and I know of people on sailboats who have gone over the side and in some cases not made it back on board. I don't spend much time around sportfishing boats and similar craft so I don't have any examples to cite from that realm. A boat with high, solid bulwarks and less need to go out on an open deck is clearly much harder to fall off of.

ron ll
04-24-2007, 04:47 PM
Gary E:

Thanks for the references. I do have an oil pressure switch that controls the alternator output and the engine hour meter. It is the only thing on that engine other than the starter that has any connection to electricity :) . I remember when I bought the boat being amazed at the lack of an ignition key or switch. Just push a button and the engine starts.

I didn't read thru those docs yet, but you might be right about rigging a solenoid to the fuel shutdown lever. You may also be right about the overboard worry, altho here in Puget Sound I have definitely heard of overboards in sailboat races often enough to not totally disregard it. I don't really have reason to go to the bow when I'm underway, but the rest of my boat has bulwarks just high enough to trip you. When I'm by myself I really minimize my deck wandering. In fact wearing a harness and clipping on on those rare occasions probably wouldn't be that much of an inconvenience. Most of the time I am nice and warm inside a heated pilot house :) .

Maybe just urban legend, but I have heard that a large percentage of recovered overboard bodies have their fly open.

Gary E
04-24-2007, 05:11 PM
I dont count those who fall over durring a blow boat race.. good heavens, they ask for it so often by tilting the deck so no one can hang on, to me that is asking to be tossed over the side. Nor do I count commercial fisherman. they are sposed to be smart enough to go back and pick up their buddy, and if they dont... well...an alarm wont help....

A individual alone and falling over is all I think that this system might help, maybe, and I have my doubts about that.
How many of you wear Seat Belts in your car? unless the STATE FINES you $250 if you dont?

Fly open... makes a good story and gawd knows the gullibe all like stories.

I love the Detroits... they wont quit till they run out of air or oil
Cant say that about the new electronic engines

Dan McCosh
04-24-2007, 05:18 PM
Re: the idea of cutting off the fuel. After reading this post, I was down in the marina today when a guy forgot to turn on the fuel for his diesel. He started it up, and it ran for more than 10 minutes before cutting off. Then I remembered this post, and asked him if he had remembered to turn in on....

Bruce Hooke
04-24-2007, 05:25 PM
The lobsterman who get pulled over when fishing on the coast of Maine (and elsewhere I'd imagine) are often fishing alone, so there is nobody to circle back and pick them up. All to often, the boat is found empty, going in slow circles, with no sign of the lobsterman. Of course if you are pulled over by your gear you are also likely to get pulled under, at which point stopping the boat is a moot point. It does not help that many Maine fisherman cannot swim. There are no swimming pools in most small towns where someone could learn to swim, and many natives in Maine view the water as being too cold to swim in.

For the record, I always wear my seatbelt. I always have. It just feels weird to me to drive without it.

Gary E
04-24-2007, 05:26 PM
Most likely he was talking about the typical shut off valve several feet from the engine, the DD STOP Solenoid is inches from the injectors, and when that is activated, no fuel gets to the engine's injectors.

04-24-2007, 08:07 PM
I can't speak for Raymarine, but since I apparently started this, the literature states the system is for monitoring crew, children, pets. As it can take up to 16 units, it isn't for the solo sailor, it's for a full house so that you know within seconds if somebody's monitor goes out of range. It doesn't take the place of safe boat keeping, it doesn't stop the engine, it just alerts you to the emergency sooner rather than later.

I've only made a handful of trips, but I know whether awake or asleep or even below sick, there was a portion of my brain tuned in to where the skipper (or other crew) was.

On the first major passage after 30+ hours of being sick, curled up in a fetal position below, I was still conscious of the feel of the boat and the movements of the skipper.

At one point, the boat slowed but I didn't hear any movement, no adjusting of sails, no turning on of the engine, no nothing. I gave it a 10 count, listened intently, and as my heart rate increased, I listened again. No movement on deck. No one at the nav station.

Fearing the worst and thinking I was alone in the middle of the ocean with a crisis on my hands, I struggled to my feet and up the companion way to find said captain taking a leak off the transom. :mad: :mad: :mad: JESUS, MARY AND JOSEPH DAMNIT!

So where I was going with this story is that if I saw the system in action i.e. gave it a test or two at the dock, maybe dropping (and weighting) one of the transponders into the water, it might relieve that sense that I feel that I always have to be on alert for any problems and allow a little better rest. :)

04-24-2007, 08:37 PM
This falling over the side seems to be of concern to many of you...
Have ANY of you fallen over?
Do ANY of you KNOW of ANYONE who did?

I know of one... and that's in over 40 yrs of being around sportfishing boats.

I know of three in the past five years: a lobsterman fishing by himself who was only barely seen and saved by another passing lobsterman, the wife of a friend (he has one arm) and she almost couldn't get back aboard, and a man last summer who was never found.

04-25-2007, 05:50 AM
Keeping a diesel electrics free is appealing to me, I would just guess quickly here that maybe a ball valve right next to the injector pump with a cable running to the helm would do the trick. A ring tied to the harness with a enough room to move about as required would seem to be pretty simple. With a break away as you fell the line would close the ball valve and a break away would keep you from being dragged.