Brass fittings and sea water…..

[NYSail]

So I’m a bit perplexed and would love some input. Just purchased a genset for boat….. nextgen 3.5kw. Unit looks beautiful and from what Ive read gets good ratings. Anyway I am installing the unit and found I would like to add 90 degree fittings to the seawater intake as well as for the vented loop based on position. So start searching for bronze 3/8 npt to 5/8 barbed fittings and cannot locate them anywhere. Called the company and was told they use brass fittings and never had an issue???? Brass in salt water. Then I called the gentleman who sold it to me and was told: 1-do not use 90 degree fittings or the engine will over heat and 2-don’t worry about the brass because it came from the factory, however he would never use brass? Seems like a strange comment.
Would love to hear opinions of both of the mechanics comments.

thanks!
Greg

 

[Captain Larry-DH]

Not an expert, but you could use it and plan to change it on a 2-3 year schedule. It would probably take at least 5 years to be a problem.

 

[dlochner]

You may have to double up the fitting, use a ⅜" to ⅝" fitting and then a ⅝" NPT to Barbed.

The 90° fitting will cause turbulence in the pipe which will restrict water flow leading to overheating. A similar situation occurs with shore based drain pluming. a 90° elbow will plug up, but a 90° sweep with a larger radius will not (or not as easily).

 

[JamesG161]

I just looked at the Owners Manual for the NextGen UCM 1 – 3.5.

1) Raw water diameter is 5/8"
2) Raw water flow = 3 gal/min
3) Water pump lift = 4 feet of water friction loss.

The really good news for you is it is the Raw Water system is galvanic corrosion protected with a ...

NPT Pencil ZINC [Brass is protected]

You must check that Zinc for loss and replace it per the Owners Manual guide lines.
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Note Friction loss in the correct size elbow is about 8 inch of water fiction loss on 3 gpm.

My point is your through hull position when submerged and flowing may not be an issue at all.

The depth of water over that thru hull adds "gravity pressure" to that intake.

If you need more help, I can size or calculate your system fittings.
Jim..

 

[Rick D]

Could those be red brass?

 

[JamesG161]

Could those be red brass?

Yes, if Zinc protected.
Jim...

 

[NYSail]

Thanks all.... you know to be honest I did not even think about the zinc as I am so use to my zinc-less Yanmars. I will religiously check them.

 

[JamesG161]

Nice unit and well laid out for access to allow service.

The heat exchanger for raw water is made from same material used in Spa Heaters

Cuprous Nickel

They designed the Pencil Zinc Size to protect it.

My Yanmar Genset had that same size Zinc.

I would suggest checking your Zinc after 100 hours of operation.

Note that for that Zinc to protect your new fittings , you must have a electron path from fitting to Zinc.
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Your Question was the fittings you needed would restrict flow.
My guess is no.

So start searching for bronze 3/8 npt to 5/8 barbed fittings

I am curious why the change to 3/8th inch.
Also note barbed suggest hoses. A non metal hose does not pass electrons.

Jim...