tstat drain plug

Coz

Active Member
Oct 9, 2018
443
Boat Info
2008 Sundancer 310
Engines
Merc Mag 350 DTS w/Bravo III
I have 3 point drain system.

My merc book says if boat is in water I have to remove water distribution plug, seawater pump plugs and tstat plug to drain.

If boat is out of water, don’t have to remove tstat plug.

Why not the tstat plug when out of water?
 
Is this for winterization or just draining the system after use?

Mine drains much faster when the thermostat plug is removed.
 
When you're in the water, you may end up siphoning the entire lake into your boat if you don't remove the t-stat plug (although unlikely).

You should still remove the quick disconnect fittings at the block and manifold (or the water dist manifold to at least first check that it's draining). If those little hoses get blocked up with sand/debris they will not drain properly - and you wouldn't know this till next Spring when you realize your block is cracked.

*Edited for clarification.
 
Last edited:
Should remove that quick crack system and go back to regular plugs. Remove and probe to insure draining
 
I’ve looked for those quick connects before and can’t seem to find them. How many on each engine?
 
upload_2019-9-27_18-38-22.jpeg
 
They are in the same exact place as any other engine that uses the normal screw out plugs. If you're really having a hard time, just follow the little hoses from the manifold. I'd also possibly suggest - and this is without knowing you - that if you're still having trouble, maybe you'd do better hiring someone to do the winterizing for you. You don't want to save a nickle just to spend a dime... although in this case, a cracked block would be a heck of a lot more than a dime! :)
 
I’ve seen the manifold ball valve. guess you have to remove the hose clamps. I hate messing with hose clamps on plastic fittings.

I’ve asked all our boating friends about the block plugs. They don’t mess with them cuz if you run antifreeze thru it doesn’t matter. Thats a combined 50-60 years of experience. Nobody has cracked a block.

Certainly doesn’t seem like a bad idea, so I will be checking those out this year.
 
Lazy and Bt

do you guys run antifreeze thru and if so, do you leave it in or remove drain plugs (blue plugs) when done?
 
If we want to talk about combined experienced, I've got literally thousands and thousands of hours. I work in the industry. And, yes, I have seen cracked blocks for the reasons I mentioned. Just because it hasn't happened, doesn't mean it can't. I've also seen where a guy didn't drain or use AF at all... and his engine was just fine in the Spring. But in the end, it's your rig and you can, of course, do whatever you want. However, doing it the proper way... in terms of the amount of time it takes... probably 15 minutes.

As I mentioned above, if you're doing things the right way, then draining the AF that helps to keep the inside of your engine from rusting defeats the purpose. Yes, I leave it in. No, I do not use the "bucket" method. I pour the AF in through the t-stat hoses after fully draining everything.

Now... did you get the right "pink" stuff? There are two different formulations - both may have pictures of boats on their labels, but only one is good for the engine (metal). The other will actually cause corrosion.
 
Yes, I got non ethanol antifreeze. I found the quick connects and verified they were not clogged. 1 was draining slowly so I cleared it with a wire. 2 cannot be seen, had to do by feel.
 

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