DIY GSM Cell Phone Bilge Alarm – Cheap Option

A cell phone bilge alarm is a great safety feature to have on board, but how can you create one affordably?

In this tutorial, you will learn how to make a DIY GSM cell phone bilge alarm. Don’t worry if you’re not up for the job there are a multitude of devices out there, and we’ve gone and listed them for you as well

Its true that all sea-going vessels and boats alike should have a bilge pump connected to an automatic float switch,  but what about an alarm? If like the majority of us, your engine makes a lot of noise and racket, then you will know how hard it is to hear your bilge pump amidst the drones of an engine.  

SBilge Alarm SwitchFirstly, to tackle this problem you will need a bilge alarm. This can be purchased for no more than £10 if you’re looking in the right places; but what happens if nobody is around to hear it? After all,  “If a tree falls in a forest and no one is around to hear it, does it make a sound?”   Well no … but it could have at least sent me a text, the inconsiderate …… !

So enter cellular bilge alarms; they have been around for some time but naturally like all marine products they cost a pretty penny. There are “marine” systems out there that are all encompassing and easier to install, however the chances are you won’t have a spare £600 to buy one.

So first of all, here is a list of all-encompassing marine systems, followed by some cheaper devices which are ironically probably the same quality anyway!

So we’ve broken it down into three options. Option 1 uses a shop bought circuit board or other device to trigger an SMS alert ; option 2 are the all encompassing marine kits and option 3 is using a hacked cell phone to trigger a SMS alert.

Option 1 – Make Your Own – The Principles

Use a bilge pump with an external float switch and an SMS transmitter. You will need a device that sends a GSM message when activated, but why you ask?

It is important that you get the correct device.  Some are used to receive GSM messages to trigger doors,  agricultural machinery etc, whereas others are designed to send SMS messages to trigger devices such as pumps and burglar alarms. Keeping that in mind you will want to find a device that runs off 12 or 24v DC. This way you can run it from your boat’s leisure battery or a secondary battery if you’re being clever. Don’t worry just keep reading, I’ve found the device for you!

Option 1 – Make Your Own – The Steps.

With quality still in mind, I have searched the internet for the most affordable cellphone bilge alarms.  I came across the company Advent Controls and contacted the director Michael Beaver. I wanted to see if he would be interested in showing us how it’s done using some simple steps.

Hi Louis,

It is relatively simply to wire a float switch to the A5 dialler. I’ve linked a float switch that can be used however, it is possible to use any float switch. View float switch 

Advent Control - Diagram - Cell phone Bilge Alarm


These diallers are all triggered by connecting the GND terminal to the input terminals which can be done with a float switch as shown in the attached diagrams.  They operate from 11V to 24V so can be connected straight to the battery.

To program the dialler you must first tell it the number of the phone which is allowed to program it by sending a SMS text to it as follows:

master <your number>.


master 07123456789.

The circuit board comes with a red jumper connector on it which can now be removed to stop anyone else adding their number.

Then if you would like it to ring your phone you simply add your number to the call list using the callnum message from the master phone:

callnum 07123456789.

If you would like it to text you, you add your number to the text message list using the textnum message:

textnum 07123456789.

You can keep adding callnums and textnums using these commands there is space for 128 numbers.

If you would like to change the message it sends you using the custom message:

customa your boat is sinking!.

You must always end the message with a full stop.

Buy the A5 GSM Alarm Auto-Dialer and SMS Sender 


 Option 2 – Buy a kit that is ready to install.

There are some more options if you’re not very tech savvy but you’ll need plenty of money.

The 20240-CA is a high water alarm with cell and email alert. As you can see it’s  a fairly expensive, however I like the robust look of the GSM sender. Maybe that makes it worth the $500, I’ll let you decide?

Boatguard and BoatWarden Alarm System are also two of the more expensive marine options available and each have their pros and cons.






Option 3 – Take your skills to the next level.

If you want to take you tech skills to the next level, you could give deconstructing a phone ago.It is possible to experiment with old cell phones using tutorials to create a transmitter. Stay away from certain key word’s like “det0nati0n”. Unless of course, you want the FBI knocking on your port side to find you with a soldering iron, a dozen mobile-phones and a  fuel container.

Thanks for reading folks – If you know of any cheaper options feel free to get in touch!


Thanks to Lucien Nunes at Rpa07 on the for thier input.

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