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Old 06-11-2019, 11:11 AM   #1
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Raw water line fitting type

Hello,
As I am redoing my raw water line from raw water pump up to exhaust manifold I need some fitting on the way. In summary I am rerouting the hoses to properly secure the tranny oil cooler and make the install cleaner.

What kind of fitting would you use, stainless 316 or galvanized steel?

I am in fresh water only, and there is quite a price difference so I was wondering if I need to do this using stainless fittings or if galvanized steel would be enough.

Thank you for any advice.

L
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Old 06-11-2019, 11:27 AM   #2
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Greetings,
Mr. L_t. Depending on the fittings have you considered brass/bronze/copper/Delrin? Galvanized will still rust where the threads have been cut.
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Old 06-11-2019, 11:38 AM   #3
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Bronze would be my preferred choice. I agree galvanized will rust, built in ongoing maintenance.
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Old 06-11-2019, 11:39 AM   #4
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Greetings,
Mr. L_t. Depending on the fittings have you considered brass/bronze/copper/Delrin? Galvanized will still rust where the threads have been cut.


Hello Mr RTF,
I checked brass fittings but in the size I am looking for (1 1/4) the cost is same or higher than stainless 316.

L
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Old 06-11-2019, 01:11 PM   #5
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I take it the exhaust manifold is iron? If so, I would suggest using bronze not stainless and definitely not brass.


Ken
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Old 06-11-2019, 01:35 PM   #6
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Vote for bronze.

Make sure anything described as bronze is actually bronze. Preferably silicon bronze. Buy from a reputable manufacturer; Perko, Groco, Marine Hardware, Sea Dog etc.

I've seen to many stores marketing brass as bronze. They are not the same. Employees might know the difference.
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Old 06-11-2019, 02:33 PM   #7
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Greetings,
Mr. L_t. Again, how about copper?



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Old 06-11-2019, 02:46 PM   #8
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I take it the exhaust manifold is iron? If so, I would suggest using bronze not stainless and definitely not brass.


Ken


Indeed manifold is iron.
Will look for bronze but may be difficult to find what I am looking for here.

Is there any specific issue with stainless that should be aware of beyond classica crevice corrosion?

L
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Old 06-11-2019, 04:49 PM   #9
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Greetings,
Mr. L_t. Again, how about copper?



Copper although used in cooling systems is not recommended for salt water.

Copper is susceptible to corrosion erosion or impingement attack. This type of erosion is caused by swiftley moving salt water through copper pipes. Since copper is fairly soft, the fast moving water erodes the inside of the copper tubing as it passes through. The erosion is more pronounced through bends and turns, especially.

Polluted water can have hydrogen sulfide in it which can erode copper.

Copper fittings attached to other metals will cause galvanic corrosion.
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Old 06-11-2019, 05:03 PM   #10
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Greetings,
Mr. s. I agree to some extent BUT the OP is in FRESH water which is not polluted to the extent some waterways in the US are. Think pristine fresh water here...


I'll notify Gardner immediately!
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Old 06-11-2019, 05:22 PM   #11
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Greetings,
Mr. s. I agree to some extent BUT the OP is in FRESH water which is not polluted to the extent some waterways in the US are. Think pristine fresh water here...


I'll notify Gardner immediately!

Do it right the first time!

Bronze fittings are readily available. Why utilize an inferior material when the difference in price is not that much.

On most boat projects, labor is equal to or more expensive than the parts.

And just because he is in fresh water should have nothing to do with it. What happens when he sells it to someone who will use it in salt water? How about polluted fresh water?

Ever try to unscrew a frozen, broken copper fitting that the walls have become thin?

Bronze fittings have thicker walls.
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Old 06-11-2019, 06:29 PM   #12
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In fact in the original setup of oil coolers fittings were copper, but the fittings were soldered.
I looked at bronze fittings but I have quite limited access to what I need like 45 degree elbows, T, nipples etc. Most of shops only sell fitting like barbs for hose.
I will try to search more tomorrow.

However if I donít get a hand on what I need is there any particular issue with 316 stainless? These one are easily accessible from an industrial provider I know.

L
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Old 06-11-2019, 06:35 PM   #13
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Copper is still the material of choice for RW heat exchangers because of cost but with shorter life.

CuNi heat exchangers last significantly longer for a modest price increase.
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Old 06-11-2019, 08:28 PM   #14
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Sure, bronze is best. But using stainless in a fresh water application would last the life of the engine.
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Old 06-11-2019, 11:40 PM   #15
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The problem with stainless is if it sits with a lack of oxygen, which is why you donít want stainless fasteners below the waterline. In this application is it gets used, itís not going to corrode. It it sits, well I donít know. Iíve had brand new fasteners eat to nothing in 3 years before I knew better, so it can happen quickly.

That said, I have a thick stainless elbow on an exhaust outlet because in some sizes bronze is hard to find. I put it on a dc generator about 5 years ago planning to swap when I got a chance. Still going strong. It sits for 6 months at a time.

I think it will work if your willing to cast a skeptical eye from time to time and check it. If my elbow fails, the boat wonít sink. It will just annoy me. That meets my own minimum threshold.
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Old 06-12-2019, 05:54 AM   #16
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Bronze may be better, but I'm not seeing a huge issue with using stainless. Exhaust elbows and mixers are commonly stainless, and have as long a life as anything in that situation. I think the thing to watch out for is any place where there might be standing water left in the fittings. If it all drains, then I would think it would be fine.
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Old 06-12-2019, 08:14 AM   #17
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Quote:
Originally Posted by Lou_tribal View Post
Indeed manifold is iron.
Will look for bronze but may be difficult to find what I am looking for here.

Is there any specific issue with stainless that should be aware of beyond classica crevice corrosion?

L

I don't really see an issue with crevice corrosion in this application. Bronze is much closer to iron on the galvanic scale which would reduce galvanic action between the fitting and the iron. Otherwise, I think 316 should be ok especially when used in clean fresh water.


Ken
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