Raw water stoppage warning.

[supermalc]

The engine on my boat is a Yanmar YSM. This is raw water only cooled. As I will be using it on rivers, weed will block the filter on the inlet on occasion. There is no temperature gauge or other warning system for lack of water. Does anyone know what I need, i.e. a low temperature sender, or water flow switch. Also where I can obtain one.

Thanks.

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[Cantata]

Index Marine (www.indexmarine.co.uk) do a neat exhaust temp alarm, has a sender that clamps onto the exhaust elbow just downstream of where the cooling water enters it. I think Halyard do one too, but the Index one is (or was) a lot cheaper. They'll have a stand at the London show where I expect you can look at it.

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[Mirelle]

That\'s the answer

Vetus also make one, but I agree the Index one is fine. It may seem odd to use the exhaust temperature to judge if the intake is blocked, but it does seem to be the best way!

<hr width=100% size=1>Que scais-je?

 

[andyball]

On the last page of latest mbm is a diy temp. alarm. Shows clamping a temp switch to the engine (same appearance switch as index's one) but could surely be fixed to exhaust in same fashion?.

Switches available from all usual electronics catalogues/websites...in various temp.ratings .


Have seen a marine system that checked water flow (can't remember where) ,but suspect it'd cost even more than the ready-made temp. ones.

Rapid electronics sell a 15mm flow-switch for £9 which might be usable if connected into water tell-tale pipe. Code 61-1546 at www.rapidelec.co.uk

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[supermalc]

Thanks very much. It's just knowing where to look.

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[chippie]

Coming at it from another tack, I helped a friend deliver a boat that had part oft the cooling water exit from a telltale pointing up and back on the transom. A quick glance showed whether it was pumping or not. Similar to an outboard really.

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[halcyon]

Re: That\'s the answer

A passing point, back in 1995 we spent a summer testing various designs for raw water intake sensing and exhaust temp sensing, and found some interesting points.
Running the engine with the raw water intake turned off made little effect to the exhaust temp on a 13 hp Vetus, took around 5 minutes to raise temp to a warning point. By this time the impellor was starting to show signs of stress.
With a sensor in the raw water intake the alarm was sounded before the pump ran dry, thus would have saved any damage.
Do people with exhaust temp sensors test them ?

Brian

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[l'escargot]

I find the clouds of steam rising above the transom the usual giveaway.

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[Jools_of_Top_Cat]

Re: That\'s the answer

I started one of my 1Gm10's this year after forgetting to open the sea cock (raw cooled). Generally the first thing I do after starting is peer over the side to see water through the exhaust, this time oddly I didn't.

I was extremely impressed by the fact the temp alarm and light on the yanmar panel started after about 30 seconds or so, no damage done, exhaust and water lock fine.

I am not saying exhaust sensors are useless here, just that the built in sensor works very well too, or at least mine did.

<hr width=100% size=1>Julian

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[Omatako]

Re: That\'s the answer

Silly question but what would one sense in the raw water inlet? That water is sea temp and a lack of it would hardly change the temperature around a sensor.
I belive the concept of sensing temerature at the top of the cylinder head is the best place but the truth is that if you have no water coming in and the engine is starting to generate steam, this type of sensor will also not send the correct signals.
Does anybody know what Yanmar systems use for their sensors? I suspect it could be metal temperature in the cylinder head because this is probably the best choice in the case of a total coolant loss. And I agree, the system on my Yanmar 3GM30 gives a timeous and unmistakable alarm. IMHO sensing a significant rise in discharge (exhaust) water temp is too late.

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[MainlySteam]

Not to be totally relied upon, but many small engine installations with wet exhausts make a distinctively hollower exhaust note if no water is being injected into the exhaust. Ours is one that does!!!!!

John

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[maxxi]

Currently I have a £1.90 (from RS) temperature switch soldered to the stainless injection elbow and driving a pietzo Sound Bomb.

On my previous boat I took the sender unit out of a scrap car radiator (the one that activates the electric fan) and araldited it to the cast iron injection elbow of the Yanmar, this activated a car horn taken from the same wreck - cost £zero.

Injection elbows run cold until someone fiddles with a seacock or a blockage occurs, either way this simple system has proved to activate in sufficient time to prevent disasters.

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[Cantata]

Re: That\'s the answer

Having suggested the Index Marine supplied alarm (with an exhaust-elbow temp sensor), I have to say that the one occasion when I forgot the open the inlet seacock, the engine ran for probably 5 mins before the alarm tripped. So the point made about damage to the impellor in that time is a good one; this alarm system probably does a good job of protecting the exhaust system components, but other parts upstream may suffer!

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[simonn]

i found the best way is a tell-tale small copper hose tee`d off the cooling system
fed up to cockpit and pointed down cockpit drain.Cheap and easy.Auto brake pipe
nipped at the outlet end will do the job.

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