Closed cooling raw water side slow to drain
 

Guys,

https://cimg6.ibsrv.net/gimg/www.off...6a06a5bcf.jpeg

This started after the rebuild last winter. In days gone by, this draining finished before we were done wiping the boat down after putting it on the trailer. Now it drips for days. This was after about an hour after backing it into my shop, which was after a half hour drive from the lake. My suspicion is that it’s the drains in the bottom of the exhaust manifolds; not draining like they are supposed to. Does this ever happen?

For context, we did add some plumbing and water-containing volume to the fresh water side of the closed cooling system, but nothing that would I’d think would slow down the draining of the system like this.

Cooling is fine. Engine runs 140-150°, unless I’m running it hard (which hasn’t happened so far this year). Oil runs below 140° at idle, and 170-190°, depending on lake temp, until I stand on it.

Thanks. Brad.

Do you remove the exhaust manifold drain plugs? If not doing so may allow the water to drain out faster. Likely a mild vacuum is slowing the draining process. That's my stab at it...

Trash,

Aren't there “automatic” drains at the bottom of the manifolds, though? That release the water when it’s not under pressure? They are the stock 496 manifolds.

Could it be that the extra bit of plumbing is applying just enough more pressure to keep the drains from releasing?

Thanks. Brad.

or a zebra mussel
🤣

Or just some gunk build up
My question do they drain into bilge every time
My engines raw water cooled.
only b thing that holds water is tube from outdrive up to the stat housing
It dribbles for about ten minutes once I get home and drop drives to drain
I hate water in bilge
Its the anal rententive part of me
End of season block draining....drives me nuts until its all dry

Powerboatr,

Nothing drains to the bilge. It all drains back out through the water pickups in the drive. It’s just agonizingly slow. It used to be bone dry by the time we put it away. Now it drains all night.

Thanks. Brad.

The 496 has balls at the bottom of the manifolds that drain the water slowly to allow for heat to be removed from the manifolds. Mine outdrive used to drip for a couple hours.

You could always apply air pressure to the valves at the bottom of the manifolds to dump the water out when you are ready to put it away. The air shrader fitting is on the top/ front of engine.

Good news , it sounds like your balls may now be working without the help of pills. :)

Sorry, my body is old, my mentality is not. :)

Is the water coming out of the pickup? Could be making it's way back past the impeller?

Bill,

It appears it is coming out of the pickups in the drive. I understand where the water is coming from, and the path it's taking. The question is "Why is it taking so long to drain?". As I understood it, the water was supposed to drain from the manifolds when the seawater pump pressure dropped off. If memory serves, this draining was complete by the time we got the boat back to the shop where I store it, and only minimal water drained out when I dropped the drive. Now it just drips and drips and drips, and I'm wondering if it was one of the several changes we made during our rebuild last winter or if it's the drain valves on the bottom of the manifolds that have stopped working properly.

For context: I added a ~2-1/2" water jacketed riser between the manifold and the elbow that also made for an 8° tilt, extended the elbows to increase the distance between the exhaust valves and the water dump, and added a sea strainer.

Thanks. Brad.

I've not messed with any 496 that new I guess. I didn't know they added a drain from the exhaust. Turns out I am no help....

Bill,

496 Exhaust Manifold

Part #s 865341A03 and 865828A02

Thanks. Brad.