I've read a couple dozen threads on these topics. Since all are a year old or more, I'll start a new one to add my questions and comments:
Engine coolantObviously MaineSail hates "Death cool", so that's out of the running. Everything I've found on this site says to use "ordinary Prestone". I don't know what the PO put in my boat, but since it was "green stuff" I topped off the reservoir with 50% Prestone Extended Life for the last couple of years, since they emphasize its compatibility with other brands/types. It's worked fine so far. But I've changed my freshwater pump this winter, and plan to flush/rinse/clean/rinse/refill my system in the spring. I want to use the right thing going forward. I was planning to use Prestone again because it's is so widely available everywhere, and I don't want to be driving an hour to get matching antifreeze if I'm in a remote area and need to top off.
However, I am also aware of Practical Sailor's Oct 2014 article that urged the use of heavy duty antifreezes that have anti-cavitation inhibitors that will prevent cavitation pitting. Drew Frye did the testing and repeated his recommendations over on Sailnet recently:
https://www.sailnet.com/forums/gear-maintenance/328002-antifreeze-diesel-engines.html#post2051576784Among his recommended brands, Zerex G05 seems to be the most widely available, and very reasonably priced. But I see no mention of it here. Is there a reason for that? If you read the article, it seems that the problem is worst for engines with thin-walled wet sleeve liners, presumably because their thinness causes them to "ring" (like a bell) and thus drive the cavitation which enhances corrosion. (Anyone who plays a brass instrument knows that thin metals ring more than thick ones.) Does anyone here know if Universal employed thin wet sleeve liners in their designs? Or is this just a Yanmar problem?
I'd like to hear your comments.
Raw/potable water antifreezeIn reviewing most of the comments about this, I saw some concerns over damage to rubber parts like impellers, gaskets, and joker valves. I agree with the general comments that these parts are
not damaged by antifreezes based on propylene glycol or ethylene glycol. However, EG is very toxic and cannot be released into waterways or watersheds, and impellers' lives will be shortened somewhat by being left compressed in the cam all winter even with glycols present.
However, some people also referred to using RV antifreeze, so I thought I'd repeat Maine Sail's warning that the cheap orange RV antifreeze uses ethanol in the formula, which will leach the plasticizers out of synthetic rubbers, causing them to harden and crack over time. Also, the denaturing agents that the Feds require to be included with the ethanol will cause a bitter taste in your potable water system that could take years to clean out (as I have learned after my PO used the orange stuff in our potable water tanks). So make sure to use the pink stuff (not orange) and read the label to ensure it does not say "combustible", as that's a giveaway that ethanol is present.
https://marinehowto.com/freshwater-system-winterizing/