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Engine Cooling water intake sucking in air (Read 4408 times)
Heber
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Engine Cooling water intake sucking in air
24.02.2012 at 22:01:35
 
Hi Guys,

I am glad to report that Hawk Moon actually did some sailing last season and is currently undergoing some close season projects in anticipation of even more adventures next year

Some of he adventures were of the type you would like to avoid, mainly the loosing of ones engine due to air been sucked in through the cooling water intake and the impeller failing.    This occurred while sailing from Peel in the Isle of Man to Ardglass in Northern Ireland.  A lovely day with a steady force 5 to 6, forecasted to drop to force 4, which did not happen.   The wind and big swell were from Port and just forward of the mast.  The problem arose when I started the engine to charge the House Battery to support the auto-helm etc.

My “perception” is that due to the hull crossing the swell at a diagonal this resulted, if not in, the actual water intake rising out of the water, then at the very least large amounts of white water been sucked into the windward cooling water intake.

Yes there would have been a heel to starboard on the boat but not greater than 15 degrees and not on a continuous basis.

I currently use two cooling water intakes, one port and one starboard, they are positioned 10 inches out from the centre line of the hull “V” aft of the end of the keel.

Question: has anybody else perceived this to be a problem?

Question: Do trapper 28’s normally use two engine cooling water intakes?

As you will see from the attached photo “Heath Robinson” was a regular member of the (inventing) maintenance crew of the boat.  From the Starboard side there is a long pipe extending over to a “T” piece in the Port side engine cooling water intake pipe. This then goes up to a strainer before being sucked to the actual impeller.

I am not happy with this layout and it may be contributing to my problem.

Question / Request:  Would you please supply photos of your layouts and maybe a comment or two regarding their effectiveness. You could email them to heber@iol.ie.

I am currently considering trying to move the “T” piece to the centreline of the boat and investigating the possibility of some form of valve system to avoid sucking in air / water from the uphill (windward) side of the system.  Any thoughts or suggestions on this please.

This is not a regular problem but if it does occur the timing could not be worse.

Any input would be gratefully appreciated.

Regards, Hebre.

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Re: Engine Cooling water intake sucking in air
Reply #1 - 25.02.2012 at 08:17:15
 
I've never heard of such a system and fail to see the advantage. It isn't at all unusual to cross over drain outlets so that the always drain despite the heel, but this system surely just means that whichever side is out of the water no water will be taken in.

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Re: Engine Cooling water intake sucking in air
Reply #2 - 25.02.2012 at 10:05:48
 
Hi Nick

Thank you for your reply.

The pipe work you can see is for the Engine Cooling system water intake.  The problem is that when no water is being taken in, it is in fact, taking in Air and that causes the impeller to fail and the engine to overheat.

I have been thinking, not necessarily a good idea in my case.  Looking at the picture the Port side seacock and vertical pipe-work above it represents a large volume of water that could drain out very quickly.  If this happens on a regular basis it would mean that the impeller would have to deal with this volume of air at the same frequency. Apparently Impeller “wheels” don’t like air.

This may indicate the need to have a “T” piece in the centre and to change the pipe-work on the port side to the same as that on the starboard side, cutting down on the volume of water that would literally fall out of the water intake in addition to the Air that would be sucked in by the impeller.

All comments appreciated.

Regards, Heber
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Re: Engine Cooling water intake sucking in air
Reply #3 - 25.02.2012 at 10:17:05
 
I would abandon one of the inlets altogether and go for a single seacock.

The idea of this arrangement may be nothing to do with heeling, it could be designed to cope with a blockage from a plastic bag or weed on the inlet, but that can easily be dealt with, whereas maintaining this system runs the risk of airlock which won't be so easily dealt with.
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Re: Engine Cooling water intake sucking in air
Reply #4 - 25.02.2012 at 17:00:55
 
I would agree - one seacock with strainer & one inlet pipe. I have never seen a twin inlet arrangements as described.
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Re: Engine Cooling water intake sucking in air
Reply #5 - 27.02.2012 at 14:41:07
 
Thanks for the replies.

I relation to the twin engine cooling water intakes, I also, have never seen this before.   This was originally set up when I was trying to address an engine over heating problem.   The basic question still applies, either with one or two seacocks.

Bringing the question back to basics.   My perception is that when crossing a big swell diagonally, that the windward engine water cooling intake appears to be clearing the water or, at least, is taking in a large amount of “White” aerated water which I think is causing the impeller to be put under pressure due to running with no water for periods of time.  This could be happening over a period of 6 or 7 hours.

Have you guys observed this as a problem with the Trapper 28 / 400.

Regards, Heber
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Re: Engine Cooling water intake sucking in air
Reply #6 - 28.02.2012 at 17:46:41
 
I can't see that the inlet could be any closer to the centreline than it is, and I've not heard of this being a problem with this type of boat in general.

I think having two inlets is the cause of the problem, a single inlet missing contact with the water occasionally shouldn't be a problem, if you are heeled over a long way you are probably best off not to use the engine anyway.
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Re: Engine Cooling water intake sucking in air
Reply #7 - 28.02.2012 at 21:55:38
 
Hi Guys

Attached please see a picture of the Engine Cooling water intakes, marked by small blobs of white tissue paper either side of the propeller .  These are approximately 10” inches from the centre line of the boat and on a flat calm day would be 1’ 9” below the surface. With the addition of crossing a diagonal swell clearing the engine cooling water intake might happen quite easily.

The reason the engine was started was to charge the house battery to support the Autohelm etc.     It did not take to long for the alarm to go off.

Again has anybody seen this as a problem with the trapper 28 / 400.

Any and all suggestions welcome.  

Again guys I am not hung up on retaining the twin engine cooling water intakes but before making any decision I am trying to get as much input as possible to base my decision on.

Regards, Heber

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Re: Engine Cooling water intake sucking in air
Reply #8 - 16.06.2012 at 08:55:24
 
I realise I may be rather late replying to this thread, but some Trappers do have two water inlet valves especially if fitted with the Dolphin Two stroke engine.  Reverse was gained by reversing the engine direction (having stopped it first!!) and then the water would flow the other way - the outlet becoming the inlet and vice versa for going forward.  Most of them ran with a 'dry exhaust' as well instead of the now more common water cooled exhaust.

Of course in this day of diesels one intake is redundant unless you drain your sink through it!!!  Best regards.

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Re: Engine Cooling water intake sucking in air
Reply #9 - 16.06.2012 at 10:51:25
 
Thank you for your reply.  Your comment makes perfect sense especially as there was a Dolphin Two Stroke engine in her originally.

I will post a picture of the (my) final solution when I take a picture of it, I thought I had one on the computer, and close this thread.

Thanks Again.
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Re: Engine Cooling water intake sucking in air
Reply #10 - 16.07.2012 at 20:57:04
 
Hi All,

As stated I better post a picture of the final solution and at least let you know what was decided on.

As you can see I have retained both seacocks and have plumbed them into a central T-piece.  So far this arrangement has worked very well.   For those who have seen other posts, regarding overheating on this engine, on this forum, the engine now runs at between 65 to 67 degrees C.   The heat exchanger had to be changed and the cooling water outlet pipe / channel through the exhaust manifold had also to be cleaned out.

Note: yes the brown material is ¾” copper pipe with soldered joints.  I am not sure if this is the best long term material but at least they will form a template to have them made in a more suitable material.  This is a cheap material to work with and allows for prototyping.  Finding somebody who could make these up in stainless steel is not easy or cheap.

Note: At the ends of the copper pipe on each connection an “Olive” has been soldered on to assist with the grip for the stainless steel jubilee clips.  In theory there should be two jubilee clips on each connection.

My next problem concerns play that has come into the Rudder Stock but that is another story.

Despite the weather have had a good sailing season so far.

Regards, Heber
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