Raw Water Flow Meter?

[SkiprJohn]

Anyone have a system that checks electronically to see if you are getting enough raw water to engine or genset or watermaker?

If so, what kind and how does it work?

regards

[Aqua Vitae]

Excellent question! I too have been wondering this same thing. Due to the overhang of my stern, it is difficult for me to monitor the water output from my exhaust. Short of posting somebody trailing in the dinghy, I am apt to stare at the water temp gauge constantly.

Now, I wonder who can actually answer it?

[delmarrey]

Fisheries Supply Search: raw water flow

If one is not able to see their exhaust I'd recommend having one. This could go between the heat exchanger and exhaust elbow or inlet the the heat exchanger. Basically, any place up steam of the raw water pump.

[jdoe71]

Here's another one:

https://www.aqualarm.net/store/comer...?idCategory=67

[Mark Zarley]

Some engines and gensets have sensors in the exhaust. In class 8 semi-trucks these sensors are called pyrometers, truckers pulling the mountains with the pedal to the medal have to monitor their exhaust temp or risk a meltdown. In boats the sensor monitors the temperature of the mixing elbow and will shutdown the engine prior to a meltdown of the exhaust hose. The engine has overheat sensors in it's cooling system as well which may indicate problems with raw water flow in heat exchangers. So to answer your question although their are no per gallon meters there are sufficient safeguards to protect your system. The trick is interpeting what your engine tells you and developing diagnostic skills. As to the H2O maker, most come with an inlet pressure guage, that provides you with information on the condition of your pre-high pressure pump filters. There is also a sensor that should the seacock be blocked (think plastic grocery bag) it immeaditly shuts down , saving your pump or pumps from running dry. One of the best tools I have found is a small hand held laser (red dot on where you want a reading) temp sensor. These can be purchased at most auto stores and are cheap. I took a magic marker and put dots on my engines as reference points so I would be "reading" the same spot . I then made a chart of all points and record the temps and dates when I take my readings. This enables me to notice small changes over time, that I might miss. Of course a big change (like in a mixing elbow, or the rear bearing of the transmission)gets my attention fast.

[Jmolan]

When I installed my Yanmar in the last boat I had. I came up with a great trick. The siphon break on most boats uses a check valve of some sort. It is at the top of the loop, abouve the water line in the eng. compartment. I understand they can get plugged with salt build up. Or shoot spray in the eng. area.
I took my siphon break hose, removed the check valve and put a "T" in it at the top of the loop. I pumbed the "T" fitting to discharge into the cockpit floor, right over a drain.
Everytime I ran the engine, I could see the exaust water spitting out down low in the cockpit. No more worries about clogging siphon valves, or salt spray in the engine compartment.
Then one day a wise crew man plugged a hose in it, and warmed his boots on a long motoring wheel watch...:-)

[SkiprJohn]

Thanks all for your input. I especially liked the one from Fisheries as it actually recommended a certain bell or horn to go with it. It also appears that they are adjustable so that they will go off when the flow goes below a certain GPM. Very handy. I just don't want to ruin a new exhaust system or the engine because someone may have thrown a plastic grocery bag in the water.
regards,

[SkiprJohn]

Mark. A lot of motoring is done while no one is actually looking at the engine or the engine is in an area where it is hard to get to to take a reading. The alarm would call your attention to a problem and then later you could use your laser to troubleshoot.
regards,

[Chief Engineer]

I just saw one yesteday....pretty simple....a length of tube that fit in a hose....had a 2psi pressure switch on it. when the pressure dropped it shuts down. I think it was for an ONAN Genset

You could probably DIY with some hose barb ends and brass pipe and a 1/8" NPT Tap

[Mark Zarley]

SkiprJohn,the point I was trying to make is our engines have built in safe guards to protect themselves from low oil pressure, overheat eng and overheat exhaust. Now whether any of these conditions are due to raw water flow can be determined by a process of elemination. Lets say we have a flow meter, and it sounds an alarm alerting us to a slow flow or no flow situation. What are some of the things that can cause this? Blocked thru hull, plugged sea strainer, broken impeller, broken input shaft rw-pump, a heat exchanger or exhaust mixing elbow that are partly plugged? In the end the first thing that will happen is the engine will be shut down, either by our noticing the rise of temps on our guages or the buzzing of an alarm followed by the engine emergency shutdown system saving itself. The point I am trying to make is we have enough "the engine is going into cardiac arrest" stuff. But I'm just a simple guy. Regards
"The Simpleton"

[boatpoker]

Jdoe71 already posted a link to Aqualarm. Theirs is a simple pipe with a gate that gets installed between the strainer and the raw water pump. As long as water flows the gate is held open. If water stops flowing the gate closes and activates an alarm. A thousand times better than an over heat alarm which often activates too late. My boat would not leave the dock without one.

[Chief Engineer]

When I worked for a Tug Maintenance company....we were asked to install alarms.....

We had to devise all kinds of strategies to make it difficult for the "Wheelhouse Engineers" to disable them.......I cannot describe the units because......
In the words of "Achmed the Dead Terrorist"

[IMG]http://t3.gstatic.com/images?q=tbn:NmkfNNpubjacBM:http://api.ning.com/files/Ux7BHEMo9Gqe9XYqRylmbICYp*SWaOhkYjl69uK1LCwKmii8vx JBst4rxyOErBmPV1tDMjQmAafxHdWqrqr-QJHGwVLD06aD/Achmed_the_Dead_Terrorist_by_Kalesta.jpg[/IMG]

"Eef I tell you, I keeel you"

[steve_hendry]

Here's another link:
Wet Exhaust Temperature Alarm by Borel Manufacturing Inc.
I've got one, but haven't installed it yet.

[delmarrey]

Originally Posted by steve_hendry

Here's another link:
Wet Exhaust Temperature Alarm by Borel Manufacturing Inc.
I've got one, but haven't installed it yet.

The problem I see with this one is by the time the exhaust heats up enough to set off the alarm the impeller in the raw water pump is already toast.

[SkiprJohn]

Aloha Mark,
I'm for going simple too. Just want to make certain I don't burn up my plastic mufflers and rubber hoses.
Boatpoker, I was wondering where in the system would be best to install. One side of the pump would be suction and the other side pressure. I guess if it were sturdy enough it wouldn't matter.
regards