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Old 30-06-2014, 05:34   #1
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More flow for cooling

Just recently I noticed the engine running a bit hot... especially at high revs.. (Volvo MD17D). The thru hull has a slotted exterior strainer and I suspect it may be blocked because clearly the amount of water being spit out the exhaust thru hull seems less than it was previously.

I've replaced the RW pump impeller although the old one seemed fine upon inspection.

I am thinking blockage within the system.... trapped debris... or at the thru hull were the sea water comes in. It's probably only 5/8" or no more than 3/4"ō...

I was wondering if putting a T on the gallery sink waste hose and running it to another T in the engine cooling intake line would add additional water volume for cooling. Perhaps a Y valve? The galley thru hull has no strainer so perhaps an inline filter would be in order.

All of this I can do in water... perhaps when the boat is hauled I replaced the engine thru hull with a larger size next spring.

Does this make sense? 2 souces of water for cooling...one being the galley sink....
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Old 30-06-2014, 05:38   #2
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Re: More flow for cooling

Galley sink waste hose? What makes you believe that is a source for raw water?
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Old 30-06-2014, 06:04   #3
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Re: More flow for cooling

Why not?
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Old 30-06-2014, 06:14   #4
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Re: More flow for cooling

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Originally Posted by Sandero View Post

Just recently I noticed the engine running a bit hot... especially at high revs.. (Volvo MD17D). The thru hull has a slotted exterior strainer and I suspect it may be blocked because clearly the amount of water being spit out the exhaust thru hull seems less than it was previously.

I've replaced the RW pump impeller although the old one seemed fine upon inspection.

I am thinking blockage within the system.... trapped debris... or at the thru hull were the sea water comes in. It's probably only 5/8" or no more than 3/4"ō...

...

All of this I can do in water... perhaps when the boat is hauled I replaced the engine thru hull with a larger size next spring.

If there's a blockage, probably the simplest solution is to just clear the blockage. Especially if your engine has been running fine for -- how many years?

I take it you don't have an interior sea strainer? Or if you do, clean it.

If there's an exterior blockage, certainly a possibility (like part of a plastic bag?), you can sometimes clear those with some judicious use of compressed air, as from a compressor or maybe even a shop vac. Close the seacock, fit the air hose tightly to the top of the valve (or the interior sea strainer, if you have one), fire up the air source and then gradually open the seacock.

There's also the possibility your engine's heat exchanger is part of the problem; it could be silted/limed up, not allowing proper seawater flow. There are products for flushing: Barnacle Buster, or some such; Triton Marine Green or some such, etc.

-Chris
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Old 30-06-2014, 06:25   #5
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Re: More flow for cooling

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Why not?
1) It doesn't exit the boat under water
2) Since there is no trap under the sink, you would suck nothing but air.
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Old 30-06-2014, 07:14   #6
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Re: More flow for cooling

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1) It doesn't exit the boat under water
2) Since there is no trap under the sink, you would suck nothing but air.
Wrong... the sink drains to through a seacock to a thru hull below the water line even when heeled.

There is an a strainer for the raw water system just at the water line..so you can remove the cap and clean it out. It's clean.
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Old 30-06-2014, 07:22   #7
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Re: More flow for cooling

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Wrong... the sink drains to through a seacock to a thru hull below the water line even when heeled.

There is an a strainer for the raw water system just at the water line..so you can remove the cap and clean it out. It's clean.
Obviously I'm confused.

Your sink waste line has a strainer on it?

Most I know of exit the boat above the water line.
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Old 30-06-2014, 07:36   #8
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Re: More flow for cooling

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Obviously I'm confused.



Your sink waste line has a strainer on it?



Most I know of exit the boat above the water line.

I've never been on a monohull that had a sink drain above the waterline.
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Old 30-06-2014, 07:37   #9
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Re: More flow for cooling

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Originally Posted by Sandero View Post
Wrong... the sink drains to through a seacock to a thru hull below the water line even when heeled.

There is an a strainer for the raw water system just at the water line..so you can remove the cap and clean it out. It's clean.

Hmmm... how does the sink water drain overcome seawater pressure?

Anyway, ref the clean raw water sea strainer, fair enough, then maybe useful to try the back pressure method. I suggested compressed air, but if you've got decent shore water pressure at the dock, backflushing with a garden hose could conceivable remove obstructions, too.

-Chris
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Old 30-06-2014, 07:38   #10
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Re: More flow for cooling

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I've never been on a monohull that had a sink drain above the waterline.

Interesting. FWIW, I've never been on one that doesn't drain above the waterline.

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Old 30-06-2014, 07:51   #11
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Re: More flow for cooling

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Hmmm... how does the sink water drain overcome seawater pressure?

Anyway, ref the clean raw water sea strainer, fair enough, then maybe useful to try the back pressure method. I suggested compressed air, but if you've got decent shore water pressure at the dock, backflushing with a garden hose could conceivable remove obstructions, too.

-Chris
I agree, fix the system you have.

1) check/fix blockage on the intake - maybe barnacle buster?
2) check the pump for wear - .5mm of wear inside the pump will greatly affect efficiency. is the cam changeable? are the seals good?
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Old 30-06-2014, 09:08   #12
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Re: More flow for cooling

If you T into the sink drain, the SW pump can suck air from the sink unless you plug it while you are motoring.
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Old 30-06-2014, 09:17   #13
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Re: More flow for cooling

Have you checked the elbow?

Mark
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Old 30-06-2014, 09:24   #14
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Re: More flow for cooling

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...I was wondering if putting a T on the gallery sink waste hose and running it to another T in the engine cooling intake line would add additional water volume for cooling. Perhaps a Y valve?...
Sorry, but this is comedy gold. Especially if you were actually serious.

Better hire a pro to troubleshoot your engine cooling system. Perhaps there is a restriction where cooling water dumps into the riser elbow.
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Old 30-06-2014, 09:34   #15
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Re: More flow for cooling

The sink drain may or may not pull air into the raw water line. Depends on how flooded the raw water suction is, IE how far below the water line.

So it would/ could work fine. However If one was to wash dishes or pour scraps down the sink while the engine is running, it could suck "Stuff" into the engine, depending on if there is an inside sea strainer or not. If not then you really want to install one anyway.

In any case either the heat exchanger is got stuff blocking some of of the tubes on the raw side, it's limed up a bit, or the discharge elbow as colemj said, is limed up, which oddly is not at all uncommon.
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