Best set up for block drains
 

I'd tap the drain plug holes out to the next size and then run the extension hose.then you can use welding wire to open up any blockage w/ ease.

I made some tools for the shop to help with the Mercruiser blue plastic wingnut drain plugs, I found them a real PITA. we have a few hand held ones and one on a flexible shaft. We always use dialectic on the thread when we reinstall them which helps for the next year.
https://cimg0.ibsrv.net/gimg/www.off...9006c47adc.jpg

I installed these on our old Top Gun. It greatly cut down winterizing time!! 3 hours of playing twister to ~15 minutes for both engines. I was worried about them falling due to vibration but never observed an issue...

https://www.directmaterial.com/stain...0-psi-wog.html

Those are pretty cool JB ^^^^^^ how long are they ??

I have installed prob at least 700 of these and always have about 40 on hand if this helps whomever. Very easy to install.https://cimg8.ibsrv.net/gimg/www.off...189ceb1812.jpg

Do these thread into the fitting in place of the blue plugs, or does the brass fitting need removed from block and these thread into the block?

They install directly in the block,

Edit: they appear to be about 1.5 inches long, so about the same length as the brass adapter and blue plug together

When I refresh motors in a couple years, these will be added. No way I can do it with engines in boat.

https://cimg8.ibsrv.net/gimg/www.off...6260cb2c7f.jpg
Could you not also run hose from the block drains, manifold drains and the sea water pump drain down to a common manifold similar to the Mercruiser system.
https://www.ebay.com/i/123060649398?chn=ps

Yeah, it was a sweet set up my old mechanic buddy suggested... They are only ~1.5 to 2" long..

The thing I liked about the ones I installed is you were still able to access with an awl to poke away and metal/rust build up...

Mine cost 3 bucks and work real good.
The reason I first did it was because the threads in the block I had got screwed up over the years. After the first winterizing I did it to every motor I touched. Straight run so easy to poke through. Brass on brass and if something is missing its a quick trip to Depot to replace.

https://cimg7.ibsrv.net/gimg/www.off...232ac360bc.jpg

Its a great idea but how are you going to stab all engine side drain holes to clear them from rust - scale - sediment - sand and so on. Thats a crack block waiting to happen down the road. These basically are the same as the OEM Merc single drain point system - one valve set up to drain the water from all those sides. That does not work down the road because you have to unclip at the block and stab the crap out of those drain holes to clear from rust and scale and sand so the water can drain out of the block. Plus other areas get so plugged up as well.

Mercruiser has a single drain point system, it has been out for 15 years give or take on the years. Anyone can buy that. One knob drains all, until it gets plugged with the usual stuff. When that happens it does not work so good.

no matter what drains or extension you put in water drain holes you still have to stab it to make sure its clear so the water can drain all out. And on the ball valve you still have to reach with your hand to manually move the valve to open it up.. One still needs the access and reach for that install. With that said if you do not have the access to install it with the engines in the boat how are you going to have access to open up the valve to drain with the engines installed for winterization ? Just asking

Not picking on your post, just using your valid point here.

In the past when I did have to go thru the drain the block at seasons end what I always did several times during the season while sitting in the slip was to pull the drain plugs and run the engines, just to flush sediment, much as possible out of the fittings/block. Honestly in many years I don't recall ever having plugged up drain fittings at the end of the season.

Closed cooling is a godsend come fall. Couple minutes and four of those little blue wing plugs and that's all she wrote.

Thread size on the blue plugs?

https://cimg6.ibsrv.net/gimg/www.off...ec7b09206e.png
https://cimg0.ibsrv.net/gimg/www.off...de73465f88.jpg
the blue plugs have an o-ring seal don't think its a pipe thread, the adapter they screw into is npt into the block,

I mentioned before a couple of times however removing plug and installing 1/4" pipe to 6 AN push loc and run hose over top of enge and secure somewhere convenient with a coupler. Makes iit extremely easy to drain once installed. If you do get some blockage just put a little air to the hose. Nice if you wanna flush your blocks from time to time also. About 25.00.

can use small socket to help for reach to undo and a very easy install as well. . These are the second most drain plugs I have installed next to the T handles I posted above. IMO really need nothing else to have for drain plugs and they are all brass. I also install these in tranny water side drains. https://cimg7.ibsrv.net/gimg/www.off...433295d6e0.jpg

BUP - do you know anything about the "season extender" setup on the newer Merc I/O's? Could it be adapted to older models?

Have experience with them all -- every single one from all marine manus. Volvo Penta has the best in the industry. The Merc air actuator / blue hand held air pump --- down the road the drain points leak and at times does not drain all the way. Anyways here is Volvo s most current one called EASY DRAIN Its been out for a tad over 2 years and won industry awards

Here's what I did. I installed a AN style fitting into the block and then attached about a 2 ft. length of hose to it. The other end of the hose is secured where I can easily reach it and has an AN style fitting with a cap on it. My thoughts are that I now have the ability to suck water out of the block or push antifreeze into the block if I want. I can also hook up an air compressor and blow air through the block. With this setup you don't have to reach any valves nor are there any valves to rust, break or stick. It's less likely to clog because the orifice is bigger and if it does clog I can clear it with air although a wire will likely still go down the hose as well. I have no idea if it will work as I haven't tried it, but it is installed and ready to go. Here's the oil drain and block drain next to each other at the top of the engine.https://cimg2.ibsrv.net/gimg/www.off...0885a3e2d9.jpg

hmmm those look great
i actually used a large home depot plumbing ball shut off
mounted it directly on block , but it is STILL really hard to reach
think thinking of trying to get hose from block, come to front on motor so it would be easier a access

this sounds like the plan!!!!!!!!

Yes, one on each side.

here is what we do on the wakeboard engine sides - the factory OEM Indmar does the same. It screws together in the middle and the 2 ends connect to the engine block side drains. You unscrew at the mid connector and that drains both sides of the block at the same time.. Very simple and well proven design.. If you every done one of these you prob would really like it. And the price to do it is very cheap.. https://cimg5.ibsrv.net/gimg/www.off...16bef68f8c.jpg