Arminius
Well-Known Member
- Oct 30, 2019
- 1,068
- Boat Info
- Bowrider 200 Select, 2003
- Engines
- 5.0L MPI, 260 hp w/Alpha 1 Drive
"Fresh water" cooled engines have mainly closed cooling systems using a heat exchanger. You must use the antifreeze specified and color coded in the manual or your engine is doomed. This admonition specifically applies to engines with compression ratios over 8.5:1 or producing near or in excess of one hp per cubic inch. Looked like the Hemi in my 2020 Grand Cherokee might need topping off and I checked the manual. I need purple OAT fluid but a little orange HOAT fluid will turn it to Jello necessitating double flushing. I had a GM XT5 with incredible factors I just mentioned out of regular unleaded. Now the 345 cu. in. Hemi makes 360 hp with a dated mechanical configuration on unleaded. The secret tech seems to be the cooling of the head passages with specific mixtures of coolant. I haven't checked marine engines in a while but Volvo-Penta obviously uses it and I suspect the Mercruiser 4.5. My Hemi manual says not to use RV coolant specifically. I found the specified Purple stuff on Amazon, no water (distilled specified) pre-mixed for $22 a gallon.