A few months ago, forum member Ando had concerns about growth inside his raw water flow sensor. As a result, he provided his sensor to me for a close examination which did indeed show some growth but not enough to affect its operation, at least that was the case on the bench. I went a step further and removed my own sensor for examination as well. It showed evidence of minor growth too but in my case, it DID affect operation. The effect of the growth inside mine caused the movable magnetic spud to stick closed. It wasn't stuck hard but it did not slide like a new one, the way it should.
During the development of the sensor for our application, added restriction was anticipated, tested and measured. Bench flow testing of an Oberdorfer M3 with and without a sensor showed a 7% flow reduction imparted by the sensor. It's important to know the test was done with a brand new, pristine sensor.
If you added a deck winch you added its maintenance too. If you added fresh water cooling, you’d have another pump and heat exchanger to maintain. Oil filtration system? Same. And so it is with the flow sensor to preserve its original performance. That is, to keep the restriction it imparts as close to the original and expected 7% as possible.
What measures could you take to maintain the sensor? You want to keep debris out of it so a decent quality raw water strainer would be important and I’m not talking about those horrible external thru-hull grates. To prevent growth inside the sensor you’ll want to flush it with fresh water as a regular part of boat clean-up following an excursion. With a flushing Tee installed it is very easy to do, takes only a few minutes. Regardless of whether you’re RWC or FWC, a regular fresh water flush of the raw water system is beneficial to the entire system too.
Here are a couple of other things to consider:
Flow sensor autopsy
During the development of the sensor for our application, added restriction was anticipated, tested and measured. Bench flow testing of an Oberdorfer M3 with and without a sensor showed a 7% flow reduction imparted by the sensor. It's important to know the test was done with a brand new, pristine sensor.
If you added a deck winch you added its maintenance too. If you added fresh water cooling, you’d have another pump and heat exchanger to maintain. Oil filtration system? Same. And so it is with the flow sensor to preserve its original performance. That is, to keep the restriction it imparts as close to the original and expected 7% as possible.
What measures could you take to maintain the sensor? You want to keep debris out of it so a decent quality raw water strainer would be important and I’m not talking about those horrible external thru-hull grates. To prevent growth inside the sensor you’ll want to flush it with fresh water as a regular part of boat clean-up following an excursion. With a flushing Tee installed it is very easy to do, takes only a few minutes. Regardless of whether you’re RWC or FWC, a regular fresh water flush of the raw water system is beneficial to the entire system too.
Pump intake flushing Tee
Here are a couple of other things to consider:
- Placing the sensor in the discharge side of the raw water pump is preferable to the suction side. It will have less of an effect in that position.
- If you have a Sherwood or Oberdorfer M3 raw water pump, their performance when they were new is less than the Oberdorfer M7 or MMI 502 pumps, worse yet after 45+ years of service so the 7% flow reduction with the sensor installed will have a greater effect with the original equipment pumps. (Hint-hint)
Comment