Peace of Mind You Can Install

Posted: October 1, 2012

Three simple alarms are easy to install and won’t wipe out your wallet.

By: John Beatty

Beep, beep, beep. Life is full of alarms. So why would I install more alarms on our Krogen 42? Because there are three things that, if they are happening, I need to know about:

- Smoke in the engine room

- Water pouring into the bilge

- Main engine overheating

The machinery space on most boats is designed to spare the captain and his passengers from engine noise and the smell of bilge water or diesel fumes. We keep our bilge dry, and I track down any smell I notice on the boat. Nonetheless, between visits to the engine room, I need to be alerted to a problem. Knowing there is a warning system in place makes it easier to relax and enjoy the ride.

Smoke Alarm

You protect your house with a $10 battery-operated smoke alarm, so why not protect the boat? A smoke alarm in the engine room won’t help unless you can hear a warning at the helm while under way. A household smoke alarm is easily adapted to give a remote warning. Gently remove the buzzer in the alarm and run wire from the engine room to the helm area. Use wire the size of modular telephone cable (you remember when telephones had wires, right?).

Only two of the four or five wires are needed. Test the alarm after you check the oil before you fire up the engine. Remember, by altering (i.e., tearing into) the alarm you certainly void any warranties.

Water Pouring into the Bilge

In our pilothouse, there is a bilge-pump panel down low behind the helm. Next to each pump switch is a red light that comes on whenever the pump runs. On our boat, this happens infrequently, so sometimes the pump runs, and I don’t notice. Nonetheless, I need to know about water coming into the bilge. It’s usually the drip from the stuffing box, but it could be a raw-water intake hose letting go (very scary) or the domestic water pump output hose coming loose. When this “demand” is sensed, all the fresh water will be pumped into the bilge. The bilge pump will then dutifully pump it overboard.

To make sure we are alerted when the pumps are running, I wired a $7 piezo buzzer from Radio Shack to the light circuit. When the pump runs, the light comes on and a very irritating buzzer sounds. The alarm can be heard in the pilothouse with the engine running and all over the boat when we are at rest.

To effect this modification, I tapped into an existing alarm system. Be sure that if you piggyback onto an existing system, you do nothing that could interfere with the effectiveness of another alarm.

Warning of Impending Engine Overheat

I think it is safe to say that all cruising boats have water-temperature sensors that tell you when the coolant is too hot — as in “about to boil.” Usually an overheat is caused by lack of sufficient water flow through the engine. Did the raw-water impeller come apart? Did you suck a plastic bag into the raw-water intake? Or did you just forget to open the raw-water seacock after working on the engine? The engine doesn’t care about the cause. It will overheat.

The first place to show signs of the problem is a spot just down from the exhaust elbow where the cooling water is supposed to enter and cool the exhaust. This spot heats up much sooner than the temperature of the coolant circuit that sets off the traditional alarm.

A hot elbow is an early warning of an engine about to overheat. A thermocouple strapped to the elbow can energize the same alarm that the water temperature sensor uses. The unit I bought from Pat’s Marine Engines in Seattle will fit on any elbow that is 3 to 3½ inches in diameter.

I took a wire from the oil-pressure sensor on the port side of the block and ran it to the thermocouple. When the engine is running, the power to the alarm system is available. If the thermocouple is heated to excess, the circuit is completed and the engine alarm sounds. Unlike many other parts and accessories for marine applications, the “system” is cheap, approximately $25.

Installing these alarms is not difficult. I did it myself. Imagine being able to add so much peace of mind to your cruising time and still get change back from a $50 bill.

It is important to reiterate: Be sure you do not interfere with any existing alarms already protecting your engine and other systems.

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