Plumbing For Volvo Penta

If what your saying is right I need to use 3.5mm wall thickness pipe, that's some pretty serious bit of piping! Tig welding is not a problem, that thickness you will weld with an arc or mig forget the tig.
maybe I will just use straight rubber and fit of to the metal bends only.

 

Depends on the diameter, you could probably go to 10s above 1" bore.
When specifying pipe thickness we make a corrosion allowance. It would be very difficult to make an allowance from 16 gauge. As I've said already, I have never seen welded stainless pipework at 16 gauge. I've only seen it used in tubing, in architectural handrailing and in vehicle exhaust pipes.

Regarding the welding, Tig and argon purging is normally used for butt-welds as it will produce a smoother, cleaner root thus cutting the risk of corrosion pits developing. If you are able to do this, then you could try using your 16 gauge, just make sure you don't leave your seacock open when you go ashore.

 

I was reminded of this thread this morning when I got this large 316 filter (it's half of a duplex set) cleaned for inspection. You can see crevise corrosion and pitting as warned against in the BSSA link I posted 11 posts up. I think it has survived 10 years but it's either scrap or a massive patch up job, depends how badly they need it in service until they get a replacement.

So I need to say that if you have stainless pipes for your seawater be very vigilant.

 

copper is fine, it is fitted standard to older volvos. get your supplies from tradelink or simsmetal.

 

what a load of rubbish. copper is the best and cheapest.

 

PVC for my raw water inlets and 90 mm PVC soil pipe for my exhaust on my twin Yanmars 250HP turbo high speed 4200RPM deisels.

1 foot of stainless steel pipe straight from the turbos ( not sure if necessary) and then to PVC.

7 years now not a prob. They run 3800RPM for hours on end.

 

Again Copper would be my first choice by a long shot for not only the fresh water cooling lines and raw water but also fuel lines as well, but the million dollar question in this whole discussion is what effect will it have on all the the other parts. Dissimilar metals and corrosion, the first to go is the Aluminum and when the hull, leg and most of of the important bits are made of it start corroding its not a good thing. I am rebuilding due to corrosion I don't want to go back there. I'm simply going buy the old rule NEVER USE COPPER ON AN ALUMINUM BOAT.
The pictures of those stainless pipes, are they constantly submerged in the salt, would you get the same thing happening on a trailer boat, the boat comes out the water drains and then you flush it with fresh water, sure there will be spots were the water will stagnate, as it cant drain totally due to the design, but the water left in there will be fresh not salty. Does this make a difference?
Actually PVC has crossed my mined many times, to use the high pressure or irrigation pipe with the high pressure PVC solvent. This may not be good for the fresh water or closed loop cooling but the raw water I cant see why not, Unless motor heat is a problem and most of these lines run mighty close even touch the motor in places. How would you also connect the rubber connection hose to the PVC, without crushing it or having it pull off?

 

i think you are worrying about corrosion more than you need to. my volvo's i always flushed at home and sometimes i would put a bit of inhibitor in the drum and let that run through. trailer boats are good that way. i also spray everything with lanolin which keeps things on the outside rustfree. but my boats are always glass or wood, never had ally.

 

I want to tread on the cautious side, but again there is so much copper already on the motor, makes you think. As I think back there is a reason why they don't use it on fuel lines, I've drawn a blank as to why. I suppose if there is a rubber hose between the pipe and the fitting, say the raw water pump and piping, there's really no connection, or is there.
At times I think to save a couple of cents now will it cost me few dollars later. Maybe buy the rubber hoses and be done with it.

 

Stainless steel is infact only stainless when exposed to oxygen, and it will corrode like any other ferrous metal when deprived of oxygen...

but in the abscence of another metal to induce galvanic corrosion it will be no better or worse than any other iron pipe.. the outside however will not corrode

 

Please give that some more thought.

Corrosion of metals is a chemical reaction with oxygen. Stainless does not corrode when deprived of O2, but neither do other ferrous metals. In the presence of oxygen, stainless does corrode, but only superficial and at a very slow rate.