Raw Water Flow Alarm

On a previous boat I had actually sucked in a plastic bag into the raw water strainer under the boat and destroyed the raw water impeller. The engine never overheated and there were no signs that there was a water flow issue as the exhaust was under water. I never want to be stranded by something like that again so I installed a water flow sensor from Aqua Alarm on our new RangerTug 31. Here is how I did it.

I cut the hose that goes between the water strainer and the raw water pump to install the sensor. I think it is a 1 1/4 or 1 1/2 ID hose. The hose is very hard to cut as there is a coil of spring steel in the rubber to prevent the hose from collapsing.

Getting the hose onto the barbed fitting was extremely difficult. I used Dawn soap and set the hose on the dock and pushed the water sensor fitting into it then double hose clamped it.

The last picture above is where I placed the switch to turn the alarm off. This is above the main helm. The siren is the small red and white circular thing. It is usually behind the switch I just pulled it up for the photo.

I ran a two conductor wire from the sensor through the bulkhead and into the space under the cabinets on the starboard side of the boat. I was unable to get the wire past the area under the refrigerator so I pulled the refrigerator out so I could push the wire up into the space just to the starboard of the closet in the main berth. From there I ran it up to the space behind the main console.

To get power I utilized the Volvo Penta system. RangerTug R31 have an accessory circuit that is activated when the igntition is essentially turned on. When the Volvo display is lit up this relay is also turned on. Like the run position on an older car. There is a separate relay for that. Ranger uses it to power the warning light to let you know that a side cockpit seat in not fully closed.

I ordered the led light that lights up when there is a water flow problem but ended up not using it. I ordered the siren instead. I don't want to have to look at the light to know there is a problem. Audible signals I feel are much better. I did not think the aquaalarm was loud enough so I found a 120db siren on ebay for less than $5. It is LOUD. You can definitely hear it even if up on the flybridge.

I put the siren above the main helm station and added a switch to turn it off. I found that sometimes you want the ignition on with the engine not running so you do not want the siren wailing by your head.

So far it has worked very well. When you start the engine just as it starts cranking I turn on the alarm. It sounds and within a second or so turns off as the water flow starts. This verifies that the system is working. When I shut the engine down I leave the alarm off. As soon as water flow stops alarm sounds. Excellent piece of mind.


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