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Old 04-06-2015, 20:48   #1
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Water pump plumbing corroded

Last year I inherited an S2 9.2A and I've recently been trying to give the engine a good going-over to make sure everything is in good shape (and to learn how things work...novice here). The engine (Yanmar 2QM15) hasn't been started in over a year.

In pulling the water pump">raw water pump this evening, I found a badly corroded elbow on the input side. What should I be looking for in a replacement to prevent this from re-occurring ? Was this corrosion caused because the elbow and pump are dissimilar metals ? Do I need a new bronze elbow (the pump is bronze I presume) or is there some better solution ? I do plan to replace the hose, btw.

Thanks for any advice you can give. I've been trying to learn all that I can but this is all new to me.

-Chris
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Old 04-06-2015, 21:06   #2
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Re: Water pump plumbing corroded

Is that a steel elbow. It looks like it. If so, yes it needs to be replaced with Bronze. Or get the correct hose connection fittings for the pump. Like the discharge side.. It looks like someone install the elbow and pipe section to mate up with a larger intake hose. I would bush down to the smaller inlet size at the sea strainer discharge and install a smaller hose.

Water flow is only about 2-3 gpm in the 15qm, so 1/2" (13mm) hose/pipe is fine.
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Old 04-06-2015, 21:10   #3
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Re: Water pump plumbing corroded

It looks like you need to replace that nipple with a proper bronze hose barb. Get the plumbing in order with the proper parts. Not a piece of pipe stuck in a hose for example. Not sure but the hose does not look right either. It should be a wire reinforced hose on the inlet side.
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Old 04-06-2015, 21:19   #4
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Re: Water pump plumbing corroded

sailorchic34, I'm guessing the elbow and short pipe section are iron since the residue has that orange-ish iron-oxide look. And yes, it looks like the elbow was intended to reduce down from the 3/4" hose to the 1/2" pump inlet. I haven't taken a good look at the thru-hull yet, but maybe I can reduce down to 1/2" there and not need an elbow at all.

Thanks for the tip on the hose, Guy. I'd only considered that the existing hose was full of crap, not that it might be the wrong kind.

-Chris
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Old 04-06-2015, 21:47   #5
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Re: Water pump plumbing corroded

You may need a zinc if there is no engine zinc or no metal to metal contact with the engine.
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Old 04-06-2015, 21:52   #6
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Re: Water pump plumbing corroded

Quote:
Originally Posted by Lepke View Post
You may need a zinc if there is no engine zinc or no metal to metal contact with the engine.
There appears to be an engine zinc. I tried to remove it to check but the whole "housing" turns when I wrench on the end nut. That's next on the list to work on .

-Chris
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Old 04-06-2015, 22:33   #7
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Re: Water pump plumbing corroded

Yes, change the elbow to bronze or stainless. My local hardware store has both. The elbow may be required to avoid excessive contortions in the hose. In your second picture it looks like you have a nice gentle curve from the through hull to the pump inlet.

The hose is size OK, It's better to have it a little oversize to supply a good flow to the pump. Wire reinforced hose is not an absolute requirement, just don't use cheap heater hose or something like that.

Make sure you have all stainless clamps, check it with a magnet.

A lot of people like to run a sea strainer, to keep trash out of the heat exchanger or block, something like this



but it does add complexity and cost. The one shown is about 120.00 for a 1/2" NPT model.

When you get that zinc fitting loose and change and reinstall it. don't tighten it like a wild man. Tight enough to not leak is tight enough.

I'm jealous of your engines paint job...
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Old 04-06-2015, 23:55   #8
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Re: Water pump plumbing corroded

It looks to me that you have a 3/4 X 1/2 reducing elbow with a 3/4" nipple to clamp the hose to. If I'm right about the sizes, you have a 1" intake hose, not 3/4, as that is about the OD of a 3/4" nipple.


This is a Reducing elbow

ACR Bronze 90 Degree Reducing Elbows


This is what you should use instead of a nipple.

The part number you want is a Groco FF-750.
It has a 3/4" male pipe thread and a 1" hose barb.

I like to avoid wire reinforced (hard wall) hose when I can. It doesn't last as long as soft wall hose. The wire rusts and damages the hose.

If you've got tight bends in the hose, you'll have to use hard wall or the hose will kink in the bend.

Trident 200 would be a good soft wall hose to use.
Trident Ply Marine Wet Exhaust Hoses -SOFTWALL Mfg# 200

If you have to use hard wall, Trident 250 is good.
Trident Flex Marine Wet Exhaust Hoses -HARDWALL Mfg# 250
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Old 05-06-2015, 08:49   #9
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Re: Water pump plumbing corroded

Wow, how was the heat exchanger and injection elbow?
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Old 05-06-2015, 10:26   #10
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Re: Water pump plumbing corroded

I don't know anything about your particular engine, but that thing that you are calling the zinc housing looks an awful lot like a valve to me.

Mark
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Old 05-06-2015, 13:56   #11
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Re: Water pump plumbing corroded

I haven't inspected anything downstream from the pump yet. There's no heat exchanger on this engine. The water goes from the pump to the "cooling water inlet connection", which is what the zinc screws into (picture above), then it splits into the cylinder jacket and bypass pipe->mixing elbow.

Thanks for the parts numbers and advice. Lots to learn.

-Chris
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Old 05-06-2015, 15:14   #12
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Re: Water pump plumbing corroded

Chris, Here's a link to the service manual for that engine. It might be useful. YANMAR 2QM15 SERVICE MANUAL Pdf Download. I think you can download it. I have the complete manual for my 3GM and reference it from time to time. When I need it, it's invaluable. SailorChic a lot of interesting posts about her Yanmar rebuild so I'd trust her comments. You don't say where you are in Texas but if you are in the Gulf, I'd definitely put a strainer in. I don't pick up a lot of stuff in mine but when I do, it's stuff I sure wouldn't want in my pump. There are lots of different types available. Parks (HopCar) probably has a suggestion or two.

Bill
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Old 06-06-2015, 07:43   #13
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Re: Water pump plumbing corroded

Bill, thanks for the link! I have a hardcopy of the manual that came with the boat but it's nice to also have the PDF.

-Chris
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