Losing water

[Brimikeg]

Good morning everyone,
First, I am a new poster to the forum, however I have read several threads in the past. That being said I have made several mistakes on this boat with this engine already and it has been a steep learning curve. Here is the issue.
A couple of months ago I bought my first sailboat, a 1969 Bristol 32. When we looked at the boat the atomic 4 engine seemed to have no issues. However when we picked up the boat the following weekend it was draining all the water from the fresh water cooling tank. Now in-between the time of looking at the boat and picking it up the PO had replaced the water pump impeller. We took the boat anyway and just continued to fill the water tank as it drained. Eventually the fuel pump died and we were towed to an anchorage. After replacing the fuel pump I tried to start her back up... Several times... With all the water valves open. I now know this is probably what caused the water I found on the spark plugs, however at the time, having only tinkered with car engines, I assumed it was a blown head gasket. So after buying an outboard to get the boat to a yard we tried to get the engine turning to test compression, only to fine the engine had seized and no amount of effort was able to get her turning again. So sticking with the out oard we pulled the A4 for a rebuild and brought the boat to a mooring. While disassembling the A4 I found a working one for rather cheap a few hours away, that PO had replaced it with a diesel inboard. It came with several extra parts and maintenance papers and had had a full rebuild sometime around the early 2000's. However the PO had pulled it after he bought the boat and let it sit outside in a yard for a while. After getting it home and making sure the compression was good I took parts off my old engine, like the new fuel pump, the water pump, exhaust manifold, and transmission (because the new one had a v drive), I then assembled it and got it back into the boat. It took me a while to get it running however because the carburetor float needed to be adjusted. Eventually however I got her running. Only to find that water is still getting pumped into the oil and I'm losing water in the overflow tank again. I have tried both exhaust manifolds, and checking to.make sure all of the water hoses from the FWC system and the RWC system at hooked up correctly. She starts with a little persuasion, but she runs with oil pressure maxed on the guage and now the raw water seems to have stoped flowing. So now I'm down to the only parts from the old engine are the water pump, carburetor, fuel pump, exhaust pipe, FWC and RWC systems. Is it possible that the MMI water pump is pumping water into the oil? I have a few rebuilt Oberdorfer Pumps that I can replace it with, I'm going to inspect for weephole leakage today. Every time I start and stop the engine I make sure the through hulls are closed for the water system to prevent water getting back in, could there be another intrusion point. I'm also going to test the water system pressure and adjust the oil pressure today. What are the odds that I have 2 engines with the same losing water problem? My assumption is it has to do something with the water pump because the engine was running fine for over 30 mins with clean oil when we looked at the boat, then he changed the impeller and now there is problems. And those problems have persisted through 2 engines with the same pump.
Sorry for the long post but I wanted to include the whole story for a better diagnosis.

[Dave Neptune]

First welcome to the MMI Forum.

Since it is doing the same thing with both engines I lean towards the exhaust system and the H/X. You could be loosing tank coolant through the H/X and have a glitch in the exhaust like a sticky anti syphon valve.

Dave Neptune

[Brimikeg]

I thought it might be the exhaust as well, however mine doesn't seem to have a anti siphon valve. It's one long pipe that goes from the engine to the back of he boat with a jacket that goes over it most of the way. so the only point the water actually mixes with the exhaust is at the transom. That being said I have seen water coming out the meeting point between the exhaust flange and the exhaust manifold because the gasket between them was not fully tightened.

[Brimikeg]

Update: I went out to the boat today and replaced the water pump, that supposed new impeller was broken to pieces. I installed a fully rebuild Oberdorfer pump. I also replaced the impeller in the raw water pump on the front of the engine. I then started the engine and was able to see water coming out the back of the boat. However there was no freshwater circulating, I pulled off the thermostat housing, I have no thermostat in there. I read somewhere a while ago before I installed this engine that FWC systems don't need a thermostat so I pulled the old stuck thermostat out and set it aside. Could that be part of my problem? Also I did a compression test on the cylinders again and got:
1 - 0psi
2 - 60psi
3 - 60psi
4 - 80psi
I also checked all the valves because I thought I saw water leaking from the valve cover ( it seems to have been water dripping from above instead) and I figured while I had the cover off to inspect the valves and all of them were functioning normally. So I'm fairly confident that it's not a stuck valve in cylinder 1.

[Brimikeg]

While on the boat today I tested the water systems separate from each other. The fresh water system if not leaking into the oil. I had a UV tracer in the fresh water and checked the oil several times after adding it and have yet to find any in the oil. So that's leading me to believe that the problem is in fact the exhaust system. I changed the oil today and messed with the exhaust system a bit to make sure there was no kinks or anything and I pressure tested the water jacket. I have a double wall copper exhaust pipe system, I have only found one thread mentioning this where Don Moyer was describing it a bit. I'm thinking of disconnecting where the water enters the exhaust pipe at the transom and running it out another through hull, would that be a bad idea?

[ndutton]

I recommend pressure testing the water jacket around the exhaust pipe.

[JOHN COOKSON]

Originally Posted by Brimikeg

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.