Please clarify Mercruiser 454 open system thermostat operation

[bud37]

Looks like you did a nice job to me.....nice touch loosening the belts and replacing o rings.....

[buster53]

Source of the post Next year...

I drain all the water our of the engine and v drive through the water drain holes and don't remove any of the hoses. Run the engine and suck antifreeze through the sea strainer....

Question is - Will it enter the block or be pumped overboard because the thermostat is closed?

That's why you remove the T-stat first as you never know when it is opened or closed. Only takes a few minutes and with it gone, all doubt is removed.

[Viper]

Source of the post Next year...

I drain all the water our of the engine and v drive through the water drain holes and don't remove any of the hoses. Run the engine and suck antifreeze through the sea strainer....

you don't need to treat the hot water heater with antifreeze separately. With the block plugs still out, pull one of the hot water heater hoses off the engine, which ever is easiest, blow through the hose (I just use my mouth) and eventually it will drain out of your block. When it finishes draining, hook up the hose to the engine again, reinstall your plugs and proceed with running the engine to draw antifreeze from the strainer. Your water heater exchanger will get antifreeze.

Before you reinstall block plugs, start the engine then shut it off right away, you'll notice more water coming out of the block which was still in the raw water pump and lines.

Source of the post.....Will it enter the block or be pumped overboard because the thermostat is closed?

Again, it WILL enter the block. I've winterized thousands. You don't have to remove the t-stat or warm it up first. Pull a block plug after if you want to confirm.

[Viper]

It might interest you to know that I've been involved with assessing several heat exchanger (closed cooling) failures and in every case except for those that failed due to corrosion, once opened up and the right questions are asked, one finds that the failures are due to not draining the exchanger properly first. For those that are applicable, you are supposed to remove the end caps per the manufacturer's recommendations to ensure ALL the water is drained out of the tubes. Simply running antifreeze through the exchanger without draining any water exacerbates the potential of failure as there is no guaranty that you'll displace all the water in every internal exchanger tube. All it takes up here is a little water left in one tube and the exchanger is garbage. At $2K, it's not worth the risk of taking a shortcut.

[jcoll]

Source of the post It might interest you to know that I've been involved with assessing several heat exchanger (closed cooling) failures and in every case except for those that failed due to corrosion, once opened up and the right questions are asked, one finds that the failures are due to not draining the exchanger properly first. For those that are applicable, you are supposed to remove the end caps per the manufacturer's recommendations to ensure ALL the water is drained out of the tubes. Simply running antifreeze through the exchanger without draining any water exacerbates the potential of failure as there is no guaranty that you'll displace all the water in every internal exchanger tube. All it takes up here is a little water left in one tube and the exchanger is garbage. At $2K, it's not worth the risk of taking a shortcut.

I know this post is a bit old but I just read it tonight. Never really gave a thought about draining the exchanger 1st. So far I've had no problems but, now I know better. Would it be sufficient to just remove the raw water drain plug, if the exchanger has one, rather than the end caps to clear it of water?

[Viper]

You're supposed to remove the end caps also if applicable. This allows you to accomplish two things; use compressed air to ensure all the tubes are clear of water and inspect for blockage from marine growth. If a tube is blocked, it won't drain properly and the blockage won't allow antifreeze to displace the water that's trapped there. In truth though, I doubt that most techs practice this and simply empty them through the drain. If they're comfortable doing it that way because they've "never had a problem before" then so be it, what ever floats your boat. You can do hundreds of them successfully that way until the one where the right conditions are perfect to set you up for a failure, so I'll continue to play it safe, retain customers' confidence in my abilities, and keep my perfect record. I don't just do mine, I do many so if just mine failed no big deal, but if someone else's failed or a small percentage of them due to shortcuts, I'd be in trouble in more ways than one, I stand to lose too much. Perhaps the biggest motivator is that I never have to go through the winter wondering if a shortcut will come back to haunt me in the Spring.