Antifreeze additive to coat waterjacket

[gravy26]

Late model A4, raw water cooled. After having the water jacket rust through at the #4 cylinder/exhaust manifold area( able to weld and repair), my thought was to add something to the antifreeze to coat the water jacket walls to prevent further corrosion while the boat sits for 6 months.
I believe public water supplies use phosphates for this purpose - would this be an option?

[Al Schober]

Let me suggest that you change from raw water cooling to a heat exchanger system with 50/50 glycol/water. Yeah, another pump and belt to worry about, but you no longer worry about the coolant corroding the block.

[sastanley]

I have an alternative to Al's suggestion. I added an electric pump for the Antifreeze pump when I went to Fresh Water Cooling, and it draws about 1.5 amps and runs on the ignition circuit.

however, if your block is rusted thru, you may need some more drastic options.

[JustinAlenScott]

Electric Pump Good Backup Option

sastanley, could you share the model of the electric pump that you use? I'm thinking that would be a very good thing to have on the boat, along with some extra plumbing, in case of mechanical pump failure. Also I'm thinking it might be very good to swap in while rebuilding my existing FWC pump (if that is viable). Thank you very much if you can set me on the right path to an electric FWC pump option.

[sastanley]

I am running the Johnson CM30. It is commonly used as an intercooler pump in Mercedes cars and some others. I have had ZERO issues and several hundred hours on it.

One more note...they have a couple different I/O sizes, so just check to get what you want. I am personally running a 5/8" input since it paired up nicely with the HX fittings, and 3/4" output, and I enlarged the side plate to accommodate. When I take off the HX radiator cap, it is furiously spinning the antifreeze around. For a while I thought about carrying a spare pump, but now carry a few pieces of spare hose, and if either mech raw pump or electric fresh pump failed, I would cobble together some way to get at least salt water thru the motor to get home.