Inner engine corrosion protection.

[ErikFinn]

Anybody knows if the Perkins M50 has such anodes? I haven't found any which doesn't mean there aren't any, and even risking looking like a landlubber I wanted to ask..

[buzzstar]

If memory serves they were not, although it may depend upon configuration, but I do not think doing so would be particularly difficult. CAVAET: do not depend upon my memory for this.

[zstine]

Do you need an anode in fresh water? I bought a fresh water boat that was repowered with a Nanni 4.150E (raw water w/ heat exchanger to fresh) and I have moved it to salt. It's been 3 years and I haven't found/serviced an anode for raw water. I spoke to a mechanic who said a lot of fresh water boats consider the zinc on the shaft to be adequate protection for the whole engine including raw water system. I think that Nanni had an anode on the exhaust elbow, but my elbow was custom made and wrapped in insulation wrap. I can't find an anode, but I also don't understand how the anode would function in the exhaust elbow... isn't that just hot/dry exhaust gas? Where can you put an anode on a Nanni? Is it ok to run without an anode in fresh water? am I correct to assume an anode is needed in salt?

[Sailmonkey]

Originally Posted by zstine

Do you need an anode in fresh water? I bought a fresh water boat that was repowered with a Nanni 4.150E (raw water w/ heat exchanger to fresh) and I have moved it to salt. It's been 3 years and I haven't found/serviced an anode for raw water. I spoke to a mechanic who said a lot of fresh water boats consider the zinc on the shaft to be adequate protection for the whole engine including raw water system. I think that Nanni had an anode on the exhaust elbow, but my elbow was custom made and wrapped in insulation wrap. I can't find an anode, but I also don't understand how the anode would function in the exhaust elbow... isn't that just hot/dry exhaust gas? Where can you put an anode on a Nanni? Is it ok to run without an anode in fresh water? am I correct to assume an anode is needed in salt?

In fresh water, given the option I'd run magnesium anodes in lieu of none at all. If there is an engine anode fitted it will most likely be on one of them end caps of the heat exchanger.


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[RaymondR]

Originally Posted by buzzstar

This more of a question than an answer, but if there is a recirculating fresh water (non-salt) system, is not antifreeze a usual recommended additive (almost a component) of the system, and does not most (?) antifreeze include a corrosion preventative? Clearly this is not true if raw water (fresh or salt is used). Frankly, I ask the question because the terms "raw water side" and "seawater circuit" made me think there were two distinct cooling systems, something I had not personally encountered.

One needs to be a bit careful with modern engines and what you run even in the fresh water side of a heat exchanged system.

Older engines generally only had cast iron exposed to engine cooling fluids and consequently no dissimilar metals to create galvanic voltages and consequent current flows. New engines tend to have dissimilar metals exposed to the cooling fluids.

My Kubuto has a cast iron head and block however the cooling water passes through an alloy timing gear cover and consequently dissimilar metals and the alloy cover will corrode away if exposed to water as a cooling fluid.

Be mindful that different metals even in a fresh water electrolyte will generated a voltage difference but because the fresh is less conductive than salty raw water the current flow will be lower, however some current will still flow and corrosion will occur.

I initially ran the engine on raw water and isolated the alloy components from it by installing an expanding nylon bush on a brass tube to carry the sea water through the timing cover. I also removed the welsh plugs from the block and installed brass bushes which allowed anodes to be screwed into them. I have since changed to an all fresh water keel cooled system and can run this on fresh water because the set up I installed for using raw water will protect the engine from corrosion.

The point of this is that it is very important to run the recommended cooling fluids in modern engines because the manufacturer will have made an assessment of what metals are exposed to the cooling fluid and the consequent corrosion potential of them being exposed to what could become an electrolyte if the wrong fluid is used.