Closed cooling - how often should the coolant be changed?

[paulswagelock]

On a Mercruiser 496, how often should the coolant be drained and replaced on the fresh water side? I visually inspected it, and it still looks good, no metallic color or sheen. Checked the ph and it is still a basic solution. I purchased the boat used, and I can not find a record of when it was done, but that doesn't mean it was not changed, I just don't know. Do I change it for piece of mind even though it looked and tested fine, or don't waste what appears to be perfectly fine antifreeze?

thoughts?

 

[SCORPIO]

Is it the green stuff or ELC coolant? If green ethylene glycol, every three years is what my system recommends.

 

[paulswagelock]

It is the factory dexcool coolant.

 

[bbwhitejr]

It is the factory dexcool coolant.

My Kohler gen and last to GM trucks recommend 5 years. It is advertised as an extended life coolant.

Bennett

 

[paulswagelock]

Yes, Merc recommends 5 years, but I did not see a recommendation for hours. My boat only has 200 hrs total, and I put on 100 in the last two seasons. The first five seasons in total were 100 hrs. I know the blanket recommendation, I was just wondering if anyone had practical experience/recommendation on changing it when it still looks and tests ok. Probably should just change it so I can start the timer from a known point.

 

[sbw1]

Follow the manual for your interval. Ph and years drive the decision. We change ours at about 5 years unless ph is off.

 

[northern]

I change mine every time I work on the heat exchangers. That is about every 5 years. The stuff always looks good when I change it. I drain all I can through large hose on the water pump fill it with fresh water run engine until hot. Drain again then repeat the process 2 more times until fluid in engine is all water. Then drain and top off with anti pure green 100% freeze. Draining the engines this way I only get 50% of the fluid out but is very simple to do. The rad shop probably does not like getting 35 gallons of weak anti freeze but they rebuild the heat exchanges so I guess I pay for the work.

 

[Skuza]

5 year intervals here.

 

[paulswagelock]

Does someone have a picture of the block coolant drain plugs? Access is tight on my boat so I would like a head start on where to go looking.

 

[mnm99]

Does someone have a picture of the block coolant drain plugs? Access is tight on my boat so I would like a head start on where to go looking.

Look near the motor mounts. It's a large allen key plug. Cant miss it..