What's the best plumbing arrangement to fresh water flush an engine with this style cooling water pickup? I've seen the 1 1/4" inserts with a hose fitting that goes upstream of the sea water pump (I think) but what keeps the water from draining out the transom pickup rather than going towards the pump?

I had a couple of pro-flush installed on my rig, the plastic cylinder has an internal spring and sliding valve that closes off the transom fitting when a hose is connected and pressurized. Remember to install in the line AFTER the seawater strainer or you will have to re-plumb it as it will get grass and other debris inside to affect the operation with the sliding valve. Had mine for two years, no problems other than location so far.

I have a ball valve between the pickups and the strainers and the flush fittings teed in after the strainers with their own ball valve. Close the pickups, open the flushers and you're good to go, then just switch them back. There are also caps on the flush fittings to doubly prevent air leakage into the cooling system.

Did a google for pro-flush and couldn't find any info. Any more information available on them anywhere?

Since I don't have thermostats I did mine this way. I have a T between the strainer and the water pump and another after the waterpump. I use the first one when I need to run the boat, the pump pulls the water in, when the motor isn't running it also backwashes all the crap out of the strainer. When I flush the motors I don't need to run them since I don't have to worry about opening the thermostats. So I just run water into the second T, between the motor and the pump.

The way it is acutally plumbed, is all the Tees, 1 1/4 x 1 1/4 x 3/4, are plumbed with the 3/4 going to a ball valve which in turn goes to a manifold. That way I hook the hose once to flush everything, then just open the valves 1 by 1 until everything is clean.

I just installed this same setup on my boat. Seen it on my buddies Cig and thought it seems like the easiest way to winterize and run on the hose w/o the fear of burning up an impellor, again.

I made the tees from 1 1/4" stainless tubing and welded on a 1/2" NPT pipe nipple, then made the 90* hose barb for 3/4" ID hard walled hose. (regular hose will suck flat). Installed right before the seawater pump, with the hose connected to a garden hose inlet mounted on the side walls.
No check valves or such. My understanding is that just turn on the hose, which will fill the line and backflow out the drive. Once the motor is started, the suction from the pump will then suck the water thru it. As long as you keep it at idle, should be fine. May get a little air from the drive, but not enough to matter. Haven't tried it yet, but looks good on paper. Plan is when winterizing, also use a tee at the inlet fitting, hook garden hose to one side, and a bucket with antifreeze to the other. After motor is up to temp on the hose, close that valve and open the bucket side and let the motor suck the antifreeze in w/o having to stop the motor.

tee with the plastic elbow was my 1st attempt, decided really don't want plastic fittings below the water line. If it were to break, that's a direct open line from the lake. I remade 2 new tees using 1/2 NPT nipples instead. Didn't see any reason to have the large non standard size as the Perko inlet fittings are only 1/2 NPT. Since a 3/4" ID hose usually requires at least a 3/4" NPT thread, I had to make the 4 90's with the 1/2"NPT thread.

an 1 " pipe tee, s.s , or install a hardin marine strainer, they have a bung in stalled in them to plumb it for fresh water flush. either way you still need a ball valve, to shut off the external pick up. we've installed this system many times and also offer it with an optional electric remote ball valve to make this system really trick.

Got to try out my install today. Mine is just a tee in front of the seawater pump, no shut off valves or anything. Plain and simple. (See my pictures above)

Worked MOST EXCELLANT! As soon as the water was turned on, it would back flow out thru the drive. Then when the motor was started, every once of the water immediately stopped flowing out the drive and was then sucked thru the seawater pump. No shut off valve needed. But would offer a bit of security in case the cap is not screwed on tight which would allow some air to be sucked in. Winterizing will be a breeze!
So easy, it's pathetic.

Just wondering how the tee has been performing. For safety I guess you can uses a shut off valve on 3/4" hose to the garden connection. I like the simplicity and wonder why many people think you need the shut off valve to prevent water escaping to drive pick up if engine suction takes care of it. My Donzi has pretty close quarters. Bob

Got any pics of your setup? I'd like to see it.