Losing water

[JOHN COOKSON]

I thought it might be the exhaust as well, however mine doesn't seem to have a anti siphon valve.

This might not apply in this instance but anyway......
When a warm engine cools it can create enough of a vacuum to start siphon of water out of the exhaust system into the engine.


ex TRUE GRIT

[edwardc]

i think that the connection between the water outlet of the jacketed pipe and the water injection point needs to have an anti-siphon valve in-between. The anti-siphon valve should be located as high as possible, at least above the waterline.

If the anti-siphon was placed at the inlet of the water jacketed pipe, that would still leave the entire volume of the jacket to potentially get sucked back into the manifold as the engine cools.

[Brimikeg]

Thank you John for the reply about the engine cooling, if the water intrusion was occuring over a period after shutting the engine off I would think you are correct, however it seems to happen immediately after shutting the engine off so I think the engine may not have cooled enough to cause the suction. However that is something I will keep in mind in the future if I noticed water intrusion over a longer period.
Ed, that's what I was thinking too, but why might it not have come like that from factory, of course I can't be sure that is still the original setup as the boat is from 1969, but the hoses have certainly been like that for a while so I do t understand why someone might not have fixed this before. There is an anti siphon valve immediately after the raw water inlet before it goes into the water pump, I don't know if that is supposed to handle the suction problem though.

[Brimikeg]

UPDATE
So I went out to the boat today, during the 2 weeks I was at school the engine just sat. So since I've been back I've been spending all my time trying to get it started again and I finally did today. And it ran strong for about 30 minutes before I shut her down. Come to find out that about 3qts of water had entered the oil. I had also noticed while it was running that there was a spatter of water coming out the exhaust pipe so some water was in there. Also the hose connecting the manifold water outlet to the exhaust pipe water jacket inlet stayed pressurized for about 15 minutes after shutting the engine down, before I disconnected it and water started pouring out of the water jacket inlet. All of this even though I ran the engine with the water through hull closed until a few seconds after no water was coming out the back hose.
My theory is that maybe there is a crack in the water jacket that opens up when it warms up? Even though none of that tracer ended up in the oil when it was only running through the block and manifold I will try to pressure test both the block and manifold tomorrow on the boat. Also, don't know if this could have nay effect on the situation, but the oil pressure was maxed out on the guage when running, but it seems like the oil pressure adjustment screw is already pretty far out.

[JOHN COOKSON]

I remember reading in the forum sometime in the past about a plug in the valve area between cylinders 2 & 3(?) that sealed a passage between the cooling system and the rest of the engine that failed.
I'm going by memory here..... The plug was part of the manufacturing process. Some of the plugs that were used were common cast iron which corroded over the years which allowed communication between the cooling system and the rest of the engine. This allowed mega water into the oil.


ex TRUE GRIT

[JOHN COOKSON]

Managed to find this. It took awhile. Post 2 #2.

https://www.moyermarineforum.com/forums/showthread.php?t=274

ex TRUE GRIT

[Brimikeg]

I'll take a look at the valves today and see if that's where the water is coming from. It kind of makes sense as the cylinders are definitely not washed clean, however I don't understand how none of the tracer would have wound up in the oil, if I'm not mistaken that bolt would allow the water from the water jacket in. But either way I'll look at that and try to pressure test the block today.

[Mo]

Ok, I have breezed through the posts here. We are missing something here. Give me a call at nine 0 two four 8 three, eight five 2 4. I'm in Nova Scotia but something doesn't seem right. Need to zoom in on this issue.

[Brimikeg]

So I went out to the boat today, instead of checking that bolt in the valve case I started with the pressure test of the block, because I figured if that passed there was no reason to look at it because it's not releasing any pressure. It did pass, it held 20psi for about 45 minutes to an hour. However when I pressure tested the manifold it held no pressure at all. I didn't pull that one off yet because I have a spare at home to I came home to test that one and it failed as well, air is escaping through the first opening on the front side of the engine.
So now I have a couple of questions.
1) how if the water is coming in through the exhaust manifold how did none of the uv tracer end up in the oil when it was run through the engine for several minutes?
2) is it possible to fix a manifold with this sort of beach in it's water jacket, or should I be looking for a new exhaust manifold?
I'm going to try to go pull the one on the engine off to take a closer look at where that leak could be.

[JOHN COOKSON]

Re plumb the new manifold using the Thatch Modification by introducing water into the manifold at its low end. This will eliminate air pockets in the manifold water passage which will result in longer manifold life.
For more info search the forum by Thatch Modification.

ex TRUE GRIT