Closed cooling antifreeze change

[oceanpearl]

Where is the antifreeze drain plug for my 454/7.4 Mercruiser engines?
Is it a required maintenance and how frequent?
Thanks for any input.

 

[paulswagelock]

It is required maintenance.
Merc recommends measuring the PH of the antifreeze, and changing it when it is no longer basic.
Normal litmus paper would work, or even a pool / spa PH test strip.

 

[Knot It]

Drain plugs are on the side of the block. Im no expert but I check the antifreeze with a hydrometer to see the level is consistent with the specified protection levels periodically during the season and routinely during the winterization process. drain and refill if/when necessary....as in protection readings are below expectations.

 

[jason78]

As I recall my manual stated 5 years for Coolant Change. When I changed mine, I believe the book stated the best way it to take out the block drains but they were impossible for me to get to in my boat so I used the alternate method of removing all the hoses around the heat exchanger and Water Circulating pump to get "most" of it out. Any way you do it, it's gonna be a mess. I had my boat pulled and bilge plugs out-Collected the coolant in 5 gallon buckets and then cleaned out the bilge.

Take belt off. It will give you better access and you don't want that coolant getting the belt.

 

[northern]

I pull a hose at the water pump (big one) and let it drain. The engine is above a non draining section in the bilge. Then pump all the anti freeze out with my hand pump that the Coast Guard requires you to have. I them fill with fresh water run engine and drain again. All the liquid goes in 5 gallon gas cans and to local recycling area that takes bulk used anti freeze. They are adamant about no oil in it so clean bilge first.
When II change anti freeze I take the heat exchangers to a rad shop to get cleaned and inspected.
Question
Should one use a flush agent when you change the anti freeze?