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Old 09-01-2014, 11:17   #1
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T'ing into the engine intake, how to avoid airlock

I have a problem-less Yanmar 4JH2E and I'm going to T into the engine coolant seawater intake for my watermaker. It's a Katadyn 40E, so the draw rate is borderline irrelevant.

I'll put T into the line, after the strainer, then a one way check valve.

Either way though, I'll drain water from water pump (I think?). Will I end up with an airlock from this and how do I clear that out?

Just trying to anticipate some problems before I start doing surgery.
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Old 09-01-2014, 11:45   #2
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Re: T'ing into the engine intake, how to avoid airlock

Don't underestimate the water flow to the watermaker. Remember the reject water quantity is a lot more than the clean water output. I would not want to compromise the engine inlet water supply.
For another idea, how about a T in a cockpit drain hose? Or anything below the water line.
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Old 09-01-2014, 11:52   #3
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Re: T'ing into the engine intake, how to avoid airlock

I had a water cooled fridge teed into the engine intake before the strainer once. Caused all sorts of problems with the engine cooling. Got used to that hollow sound from the exhaust when the impeller is not getting any water. I would not tee anything into the engine intake. Not worth the potential hassles.
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Old 09-01-2014, 12:02   #4
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Re: T'ing into the engine intake, how to avoid airlock

Splicing into the engines intake cooling line is universally accepted by most all major watermaker manufacturers as a big no no. I would say most all manufacturers of all kinds of water cooled systems would agree as well. You're better off taping into a head intake or wash down line etc.
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Old 09-01-2014, 13:23   #5
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Re: T'ing into the engine intake, how to avoid airlock

Yeah, you probably don't want to hear this, but I think the best way to avoid problems with your engine intake is to leave it alone.

Good luck, whatever you do.
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Old 09-01-2014, 13:35   #6
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Re: T'ing into the engine intake, how to avoid airlock

Eric,

Does it say anywhere in the watermaker manual what the incoming flow rate has to be? I, too, feel concerned about the possibility of compromising the cooling water intake for the trouble free engine, while it's running, the watermaker will demand a lot of sea water, and they run for quite a while. FWIW, on our old boat, Jim used the head intake for the watermaker, because it was a short run, and had good access to the settee water tank... There were no troubles with the installation.
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Old 09-01-2014, 15:26   #7
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Well seeing as the 40e passes about 15 gallons per hour I don't see a problem here.

There will be no air pulled back through the 40e

The air that is introduced by opening the plumbing connection will be no problem for the engine. The impeller is self priming and your engine is mounted low enough for the water to flood the pump anyway.
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Old 09-01-2014, 16:15   #8
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Re: T'ing into the engine intake, how to avoid airlock

Regarding Suction pressure at the "T". Several unknowns, how clear is the skin fitting/can it be enlarged/is it big enough. If you need to run both, suggest you start the engine first.
If you ran the water maker pump on its own, worst case you could suck air thru the engine, water maker may have a issue with that (or image a plastic bag cover the intake), but also the Engine may not be immediately available until the raw water pump self primes.
Is it possible to fit the "T" and bench test the implications on the engine with a similar capacity pump as the water maker.
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Old 09-01-2014, 16:19   #9
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I think what everyone here is missing is that the Katadyne 40e is a 1.5gph watermaker. The extra flow demanded of the thru-hull fitting will be almost immeasurable as compared to the maximum required by the engine. If the watermaker pulls a touch of air the world will not end either.
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Old 09-01-2014, 16:22   #10
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Re: T'ing into the engine intake, how to avoid airlock

Air into the engine is not the issue here, the engine will survive this minute bit of air just fine. The vacuum created by the engine cooling pump is the issue. A 40E will be sensitive to a intake vacuum and it's already low output performance will suffer even more. This becomes an issue especially with such small capacity watermakers. Most people want to run their watermakers while they are running their engines for obvious power and charging reasons. A 40E usually will see a lot of run time hours because of it's anemic output. I believe Rebel has a family of four aboard so long run times would be a normal expectation. Not having the ability to have his watermaker at optimal output during the time he is running his engine doesn't make sense at all. This setup he is contemplating has been done many times before usually with far more hassles than it's worth. Not to mention possible earlier than normal wear and tear on his watermaker. Use another thru hull for watermakers or install a dedicated one.
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Old 10-01-2014, 09:08   #11
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Re: T'ing into the engine intake, how to avoid airlock

Quote:
Originally Posted by rebel heart View Post
I have a problem-less Yanmar 4JH2E and I'm going to T into the engine coolant seawater intake for my watermaker. It's a Katadyn 40E, so the draw rate is borderline irrelevant.

I'll put T into the line, after the strainer, then a one way check valve.

Either way though, I'll drain water from water pump (I think?). Will I end up with an airlock from this and how do I clear that out?

Just trying to anticipate some problems before I start doing surgery.
I was convinced it would be ok, and did not listen to anyone's advice.
I commissioned my watermaker in 2006 and ran that setup for 6 years. I could only run it while engine is at idle in LOW RPMs. Otherwise it would overheat due to lack of raw water flow. In 2012 I finally gave up and decided to take watermaker feed else where. Took it from cockpit drain seacock. For few years i was swapping the drain hose with intake hose. and its becoming a headache. I really need to drill another hole dedicated for watermaker feed.
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Old 10-01-2014, 09:32   #12
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Re: T'ing into the engine intake, how to avoid airlock

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Originally Posted by Tellie View Post
Air into the engine is not the issue here, the engine will survive this minute bit of air just fine. The vacuum created by the engine cooling pump is the issue. A 40E will be sensitive to a intake vacuum and it's already low output performance will suffer even more. This becomes an issue especially with such small capacity watermakers. Most people want to run their watermakers while they are running their engines for obvious power and charging reasons. A 40E usually will see a lot of run time hours because of it's anemic output. I believe Rebel has a family of four aboard so long run times would be a normal expectation. Not having the ability to have his watermaker at optimal output during the time he is running his engine doesn't make sense at all. This setup he is contemplating has been done many times before usually with far more hassles than it's worth. Not to mention possible earlier than normal wear and tear on his watermaker. Use another thru hull for watermakers or install a dedicated one.
+1 on what the expert says--I teed into the washdown pump for both water and power.
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Old 10-01-2014, 09:43   #13
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Re: T'ing into the engine intake, how to avoid airlock

The PO of my boat put a T in the engine intake line for cooling water for the A/C pump. Since the A/C only runs on shore power it doesn't "compete" for intake water. He did install a shutoff in the A/C branch because the engine was running hot and he thought it might be an airlock problem. It still runs hot at higher RPM's. (It is a Perkins 4.108) If I can't solve the overheating problem by replacing the thermostat and cleaning the heat exchanger I am going to try separating the two intakes.
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Old 10-01-2014, 19:00   #14
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Re: T'ing into the engine intake, how to avoid airlock

I would want to be 100% sure that at full throttle both the engine and water maker would be getting plenty of flow. Seems like a no-brainer that a thru hull and strainer are best practice, even know the water maker has little output.
Rebel I've been reading your posts for several years and am abit surprised you asked. I'm a engine nut, sailing is secondary for for me. Let the engine retain it's well proven working system and drill another hole. I prefer not to have anything tee'd into the head intake as well, it's not uncommon to get a tiny bit of back wash on a manual pump head. Some people hate thru hulls but I see them as a necessary evil. The biggest bummer I see about this is the haul to do it right, a possible $300-$400 for 20 minutes work. I prefer to use 5200 fast and let it set before splashing but that's not always easy at a random yard .
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Old 10-01-2014, 19:44   #15
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Re: T'ing into the engine intake, how to avoid airlock

Simple answer: WHY?

Worst possible place to do so.

Use the head intake if you have to split something like that.

Withg a watermaker, I'd be running the engine for power to use it, so why compromise something important? Like your ENTIRE engine?
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