Changing Raw Water Impeller--water ingress!

[Dmeistar]

I was recently attempting to change the raw water impeller (for the first time) on my Yanmar 4JH3E. I closed the raw water seacock and unbolted the pump cover. As I removed the last bolt, sea water started leaking out. I expected a little bit to come out. I grabbed a little dish to catch the water, and dumped it into a bucket. The dish filled again. And again. The bucket filled, then filled again...I think you get the idea. Water just kemp coming into the dang boat. All in all we probably had about 10 gallons of seawater flow into the engine bilge. I double checked the seacock--definitely closed. I opened it just to see what happened and then the water REALLY started coming in.

I thought maybe a siphon was forming somehow, but our exhaust exits above the waterline. It seemed unlikely, but I thought maybe the seacock was not working right and letting some water through. I removed the hose clamps and hose, and its not letting any water in.

Any idea whats going on here? Is it normal for water to keep pouring in like this?

Thanks,

D

[DougR]

Sounds pretty normal to me.......you have the water in the hoses from the pump to the heat exchanger, to the gear cooler, up to the vacuum valve, and then you have all the water in the heat exchanger itself as well as that in the gear cooler. It looks like a lot, but I doubt it's 10 gallons.

But anyway, now you have the experience of changing out the impeller, and that's all good.

DougR

[model 10]

In a far-off land, you could be draining the water lift and the exh hose. Otherwise there is not 10 gal of salt water in the engine.

[a64pilot]

No, 10 gl doesn’t seem normal, I’d try to figure that out before I ended up with a water locked motor.
I’d guess mine is a quart or maybe two? It ought to be just the water in the heat exchanger and the little in the hose going up to the vacuum breaker as the exhaust hose connected to the elbow had best be pointed down and dry up by the engine and the hose past the breaker drains into the exhaust elbow.

[dougweibel]

I agree with a64. I have a 4JH3E and agree with a quart maybe two. The arrangement of your anti-siphon, heat exchanger, hoses etc. could lead to a larger volume but nothing like 10 gallons unless you are somehow siphoning water back from the muffler. That should only happen if the exhaust elbow were full, which would be a bad/unusual situation as it would mean you've got seawater sitting in your exhaust manifold all the time.

Please post if you get this figured out. Seems pretty mysterious to me.