What you describe looks to already be there in prestone antifreeze so what is the need to add more?I was wondering if anyone uses a product like prestone anti rust inhibitor and water pump additive? It does not contain stop leak just anti rust and lubricants..
Supposedly the antitrust additives in pristine wear out so that is why they say to replace it every few years. So why do that if you can just replace the additive??
IF antifreeze protection is not required where you boat , 100% distilled water , with water pump lube works fine.
But it too must be changed out every so often.
Cost is not the big advantage engine cooling is .
Antifreeze only has 5/8 the heat transfer ability of water , cars use high pressure caps (15-18PSI) to overcome this, but most old boats have 2 or 3 PSI cooling systems .
In Fl we use 1/3 antifreeze 2/3 distilled water and a can of WP lube .
Supposedly the antitrust additives in pristine wear out so that is why they say to replace it every few years. So why do that if you can just replace the additive??