nomadwilly wrote:Well.........It's not every day someone calls my posts "meaningless". ...
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That's a good point Marin about the heat exchanger. I just replaced the zincs in my engine heat exchanger but found none on the transmission HE. I should probably replace it occasionally. How long should they last.
Eric-* I didn't mean to imply your post was meaningless.* Just that in the overall scope of things the difference in bearing wear between ATF and lube oil in*something like a slow-turning Velvet Drive*is probably meaningless.* Maybe that's the wrong word.* Maybe "irrelevant" would have*be better.* In any event, it's sort of like debating which is better, a brown rat or a gray rat whent the only really important thing is that you need a rat.
I can't speak for the kind of engine you have, but none of the curpro-nickel*lube oil and transmission fluid heat exhangers (the FL120 uses the same model cooler for both applications) have zincs in them anymore, at least not the ones I buy through Amercian Diesel.* When we bought the boat, one oil cooler on one engine was old enough to still have a zinc and a tab for a bonding wire.* The new ones I've bought don't have either of these features.*
According to one of the more experienced folks on the GB owners forum, there are heat exchangers of this type that are still made with a zinc holder and wire tab.* But I don't know who carries them.
The big engine coolant heat exchanger does*have a*zinc*in it, a replaceable pencil zinc.* I check it every six months or so, and while there is always half or more*of it left, I go ahead and replace it.* The first time I let them go a year before I checked them and while there was still some zinc there it was getting pretty small.* So*I decided on a six month check.*
My guess*is that*the*longevity of this zinc is dependent on several variables, same as the ones on your hull are.* So where six months works for me, someone else with a different boat, different engine, different elecrical setup, in a different marina might have to change it more often or less often.
There have been several discussions on the GB forum about whether or not heat exhchangers should be electrically isolated from the engine or not.* Our diesel shop says no, and in fact has advised me to remove the paint on the small oil and transmission coolers*where the mounting bracket grabs them to make an electrical connection between the exchanger and the engine.* This is perhaps one reason why these coolers no longer are made*with zincs and wire tabs--- the cooler can be tied into the boat's bonding system through the engine.
The theory that's been posed about isolating the main exchanger is that if it's connected electrically to the engine, it's possible that the cooler zinc may*end up being a sacrifical anode for much more than the cooler itself, thus eating up the zinc in a big hurry.* I can see the*validity in this theory, but there are a lot of variables that would have to line up to make this happen.* It's certainly not happening on our boat (our cooler is bolted to the engine).
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-- Edited by Marin on Friday 10th of September 2010 12:37:03 PM