Winterizing the boat and went to drain the headers and hardly anything comes out, we were on Table rock about two weeks a go so I figured they would be full as usual... is it possible that a four hour pull home could of sucked all the water out ? there is no way it all could of evaporated in that short of time.

You have any O rings for the butterfly valves missing? I now i bought some aftermarkets ones a while back and they dripped all the time.

I would think not, what type of headers are they? I know I have pulled mine home 3 hours and left it sit for a couple of weeks and still had quite a bit of water in them. Are all 4 the same or did some have more than others?

Last season when I drained my stellings I didn’t get much at all and all four were about the same. When I took the tails off spring more water came out than what I had drained. This year I’m going to put air into the dumps after draining. Not sure if it was the angle or what but didn’t appear to.

My CMIs use the rubber distribution tubes and I have drain valves worked into the connection. I’ve seen them leaking some. A couple times I’ve forgotten to open the valves after flushing and found them and my heat exchangers empty. It doesn’t take much of a leak at all to drain them.

Water leaking back through the pump/impeller? I have pretty much always noticed that over an extended period, water leaks back through the pump and out the drive to height equal to the drive inlet level.

Headers are CMI sweepers with the welded distribution connections, O rings are fine and plugs were tight, strainers are still full so I guess it could leaking back but it would have to go up to the T stat housing to drain, kinda perplexing.

Suction could pull it through the thermostat housing. Siphon effect?

Possible Tom.........not running a thermo stat wide open with a cross over, there was no more than a trickle out of three of them and a few table spoons from one

Header leak test time brother. Better safe than extremely sorry.