8.1 Horizon Coolant Change

JMD

Member
Jul 31, 2017
33
Chicago
Boat Info
2006 Sea Ray 340
Engines
8.1 V-Drives
I've read up on the gymnastics required to change the coolant - but I want to be sure I purchase the correct type. Currently, the coolant is pink - and about 5 years old.

Can someone confirm that this would be the correct fluid?
Prestone Dexcool
https://www.pepboys.com/prestone-dexcool-50-50-antifreeze/product/9307805

I plan to buy 5 gallons per engine - Will this be enough for the top off as well?

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edit: for some reason the clickable link above is not producing the same page as copying and pasting the link... Sorry.
 
Our coolant is pink Dexcool The idea is to make sure you do not mix pink with green as the engines will be badly damaged if you do mix them. Are you sure you need to change them out? Most knowledgeable skippers monitor ph. Fresh Dexcool is alkaline, maybe 8.5? It gradually becomes less so. My five year old coolant is now down to 8.1 and 8.2 on the mains and 8.3 on the genny. When one engine reaches 7.5 all get changed. Technically 7.0 would be ok also. Our boat is Crusader powered and I do not know how much fluid a Merc requires. I'm sure you could go to the Merc web site and find this out. Also read your owner manual section that deals with fluids and specs.
 
20 Quarts is spec for a Merc 8.1. Recently changed mine. And as sbw1 said, a pox on your engine if you dare mix colors! You want the red/orange Prestone stuff. It's cheaper if you buy the non-premixed stuff and add your own distilled water. I was too lazy and bought the premixed 50/50 stuff. Best price seems to be Walmart but your results may vary.
 
Correct, Dexcool mixed 50/50 with distilled water or buy premix. It takes 19-20 quarts total so 3 jugs straight or 5 premix will do you. Not that bad to change.
As mentioned, you can get litmus strips and measure alkalinity of just change every 5 years or so.
 
Tip:
Catch the drainage with a shop-vac - big one, capable of holding 5 gallons. A clean bilge is a happy bilge.
 
I was initially worried about using Dexcool on my engines after reading some articles.

Apparently Dexcool when mixed with normal green glycol can gel and block vital coolant passageways within the block and head. From the articles I read, Dexcool "haters" began to emerge after GM mistakenly building certain V6 engines with the wrong head gaskets that didn't mesh with the engine's required Dexcool. It started dissolving the gasket material, so what some owners did in a panic was to drain the Dexcool and replace it with green glycol to avoid the "gasket eating Dexcool disaster". Of course, there was usually some Dexcool remaining in the cooling passages which mixed with the newly introduced green glycol, creating pocket of gel which blocked some of the cooling passages and the engine was damaged from hot spots. The fix from GM eventually was to admit the wrong gasket material was used and replace the head gaskets on affected engines (not sure if they ever did a recall).

The good news is our 8.1 engines were never part of this issue. The proper gaskets were always used from the factory that don't have any issues with Dexcool.
 

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