As a testament to how good bronze or 'naval brass' is, I offer this evidence.
In 1998, I got this boat. I found out all 4 cast iron Bar 20.0000 riser were rusted out and some leaking internally, outside looked ok. So I bought 4 risers for $1000.
Lots of money to me!
So I wanted to make the risers all FWC.
I modded them to do this.
So from Hampton Rubber, in Hampton VA, I bought two 2.5" 12 inch pipe bronze nipples and two SS 3/8" 12 inch long pipe nipples.
I asked HR, and was told the pipe is 'Naval Brass'. It is not bright yellow color. It is more reddish color.
I cut them in half, so had 4 pieces of pipes
And four galvanised 3/4 " elbows and two close nipples.
I brazed shut the water exit hole in the riser.
I knocked out the upper core plug in riser and brazed on one elbow. OEM water inlet was already threaded, so attached elbow there. This was then included in the FWC cooling circuit of exhaust manifolds and engine block.
I brazed on the 2.5 inch bronze nipple to risers exhaust exit.
Drilled a hole at an angle and silver brazed SS pipe to the bronze nipple. This takes the raw salt water for cooling.
Here is the part in 2016, was new in 1999. Bronze pipe is to left, red hose is salt water. The other 2 hose hookups are FWC.
The bronze welded on part and SS pipe are in perfect condition after 16 years of use in ocean water with hot exhaust and salt water running through them.
No rust on the inner water passage of the riser. However the cast iron exhaust surface exposed to hot salty air-fumes-vapors will still rust.
Looking down the exit pipe
Other end of riser
I have been thinking If I live long enough, I would buy some SS 304 elbows and pipes and make a new dry riser. Cut off the bronze pipe and turn it around screwed into the upper elbow. I think these risers still have another 15 years of life left.
The riser attaches to the log manifold by way of this adapter. I had new ones made of steel, but they were rusting, so I coated on with braze this time. And earlier one I had coated 2 years ago with Permatex Ultra copper, and no rust, it also withstood the exhaust heat.
I carefully cleaned some carbon off and you cans see the red gasket maker is still on the inside surface pipe. I was very impressed considering hot exhaust is very hot.
SO I recoated for another test this part with Ultra Copper.
This time both inside and the outside are coated. I just used my finger to smear it on, really does not take that much silicone gasket maker. It turns into a soft rubber coating. The inner surface I put on two coats.
So I hope you see the pics.
I have also coated an ONAN gen exhaust which always rusted between block and where the cooling water exists, too hot to hold paint, but this Ultra copper it stays on the metal and no more rusting.
