Blocked water intakes.

J

John Banfield

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24' Natant, Beta inboard. blocked water intake, over heating alarm activates. Need a bit more warning, any thoughts on raw water intake flow meters to indicate restricted water flow to engine. Sea weed the problem, lots floating around this year, I also tend to go into coves etc with shallow water. Any thoughts on a cost effective solution.
 
there are some kits that clamp on the rubber flex hose of your exhaust and have small tempsensor that reports when exhaust temp increases. Someone will come soon with a link. If you search, there was discussion on these a couple of months ago.
alternative (complex) solution is a pressure sensor on the heat exchanger intake that can warn for low pressure (blocked inlet) or high pressure (blocked heat exchanger!)

btw, welcome to the forum!

V.
 
There are also water flow alarms available that go into the raw water hose just prior to the injection point at the exhaust elbow.
These will sound an alarm IMMEADIATELY the water supply fails and before any temperature rise in the exhaust hose.
I will be fitting these to my TAMD 61A's
www.aqualarm.net
 
AndieMac said:
I recently heard an owner mention he installed an alarm sensor on the cover plate of his Jabsco raw water pump. If a blockage occurs at the intake, the first thing that will get hot will be the raw water impeller.
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I suspect the uncooled exhaust gases - about 400 degrees(?) - coming into exhaust pipe at hundreds or thousands of litres per minute will raise the temperature in the exhaust pipe from its normal temperature ( about 50 degrees?) way faster than the friction from the still wet impeller will heat up the water pump cover.

£50 for an exhaust sensor from Silicon Marine, c£75 IIRC for one from NASA Marine, or home made one for maybe £25?
 
Funny our twin cummins with the silicon marine kit sit all day at 32 degrees with 23 degree water - however at just above idle - ie 900-1200rpm - its creeps up to 70+deg pretty quickly. We have the graphed version of the silicon marine one - but even the simple ones are actually quite smart and have nmea output too..

Steve
 
Any of these systems are a great thing to do and will give early warning of impending and expensive disaster.
I used to live near Donnybrook in WA Steve :)
 
5teve said:
Funny our twin cummins with the silicon marine kit sit all day at 32 degrees with 23 degree water - however at just above idle - ie 900-1200rpm - its creeps up to 70+deg pretty quickly. We have the graphed version of the silicon marine one - but even the simple ones are actually quite smart and have nmea output too..

Steve
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it would be good if it had NMEA2000 IN so that it can have a temp alarm mapped to RPM Steve :-)
turns out that a seawater pressure sensor would be more reliable. MAN have it in their bigger engines and I guess all the other players do so!

V.
 
Silvercloud said:
Any of these systems are a great thing to do and will give early warning of impending and expensive disaster.
I used to live near Donnybrook in WA Steve :)
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A little far from us but lovely part of WA.. we are heading down that way in a few weeks.. with the tinny in tow.. and yes agree - it doesnt matter which you use.. they all will save a disaster - some earlier than others!

vas said:
it would be good if it had NMEA2000 IN so that it can have a temp alarm mapped to RPM Steve :)
turns out that a seawater pressure sensor would be more reliable. MAN have it in their bigger engines and I guess all the other players do so!

V.
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I'll leave you to design that VAS :) - Yes the Seawater pressure or flow sensors are the ultimate - but some of us dont have the luxurt of a straight enough piece of hose to put them in :). I recon my in hose sensors would pick the water shortage at cruise speed within a few seconds.. not that I want to find out again!

Steve
 
5teve said:
I'll leave you to design that VAS :) - Yes the Seawater pressure or flow sensors are the ultimate - but some of us dont have the luxurt of a straight enough piece of hose to put them in :). I recon my in hose sensors would pick the water shortage at cruise speed within a few seconds.. not that I want to find out again!

Steve
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I already have Steve, even installed it on the 2GM on my generator.
I just drilled a hole on the first endplate of the first heat exchanger after the impeller and bolted a short flexhose with the 5bar (iirc) sender on top. Main problem was sourcing a cheap sender tbh. Got a plastic case one and touchwood it's fine on it's 2nd season.

Not sure about the flow sensors though. wouldn't like to compromise the flow with a propeller spinning in there. actually bought a few from ebay for a fiver, turned up to be of such an attrocious quality I wouldn't place them in the garden hose to measure how much water my plants need :rolleyes:

V.
 
Apart from sensors which I endorse. I have the Silicon Marine ones 5teve has, I have a similar issue with barnacles clogging the intakes on my outdrives and seacocks. You didnt say if you were picking up weed or if it was growing on your intakes causing the blockage. In the event it's growing I experimented last year with a thin layer of waterproof grease and was surprised and delighted that nothing apart from diatoms grew on it and surprisingly it lasted nearly 5 months before I needed to reapply despite being in direct flow of a planing boat. It costs nothing to try if you can get to your intakes easily enough and you may also be as happy with the result.
 
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