Do I have a blown head gasket

[boatnerd]

Remove the exhaust manifold and have a look in the ports. Are the insides of exhaust ports dry carbon or wet and oily. If wet does it smell of coolant? Coolant loss could also be the rubber end caps on the Bowman heatexchanger.. but Im guessing its probably headgasket if your getting hydrolock symptoms when trying to start. .

[captchetco]

Originally Posted by Ecos

No, the gases will blow out of the cylinder into the water. Even with a leak, there is way more pressure in the combustion chamber than the cooling system.

Caveat:
When you shut down the engine, the Oil Pressure and Cumbustion pressure quickly drop to -0-. The water pressure will, however, very slowly diminish over up to 2 hours, during which the coolant pressure is greater than either the oil or combustion.
However, the symptoms indicate most likely The sea water to coolant heat exchanger is leaking between the systems, also a possible problem in the water cooled exhaust manifold if existing.

[skipmac]

Originally Posted by boatnerd

Remove the exhaust manifold and have a look in the ports. Are the insides of exhaust ports dry carbon or wet and oily. If wet does it smell of coolant? Coolant loss could also be the rubber end caps on the Bowman heatexchanger.. but Im guessing its probably headgasket if your getting hydrolock symptoms when trying to start. .

This is something I wouldn't mind doing for a couple of reasons. I know of a couple of sisterships that had to repower because the way the engine is installed if the injector elbow corrodes internally, after shutdown the last bits of raw water in the system can drain back to the exhaust valve in the end cylinder.

But the way the exhaust elbows are installed the nuts holding them on are really difficult to access, one of those 1/16 of a turn, flip the wrench, another 1/16 of a turn, repeat 10-12,000 times. Also having been there 35 years probably would take dynamite to get them loose.

[dbraymer]

I did not read the whole thread, but pressure testing is DIY and very cheap. You can do it with a bicycle pump. Just pressurize the cooling side with the engine cool and still. If you have a head gasket leak, water will probably enter the exhaust system, or a cylinder.

I had a 4-154 and I was losing water, and it turned out that a cross over tube had a low point leak thru (pin hole), not a head gasket leak. The leak thru stopped when the engine was not hot and running, so it was difficult to find the leak, but pressure testing showed a drip with the engine not running.

If the test ends up showing water dripping out of the exhaust system raw water entry, it points to the exchanger tube. They can be re-soldered, a new one costs about 800.

[skipmac]

Latest update, the problem may be solved. Picked up a couple of diagnostic tools that helped a lot.

First, Autozone will loan you radiator pressure tester which is a $150-$200 kit that includes about a dozen different adapters.

1, Tested the heat exchanger (after jury rigging it to the radiator pressure teste) including a boiling water bath, then reinstalled and pressure tested the system and found a leak in one of the hose fittings. It was under a motor mount and drained down the side of the engine bed so pretty much invisible.

2. Reassembled everything and pressure tested the system. Turned up a small leak which I fixed. It was under the engine next to a motor mount and virtually invisible. After fixing the leak retested and the system held pressure perfectly.

3. In the process of testing I again had to keep adding water but also after running the engine when looking for leaks I heard a loud gurgle which was clearing water and air moving around. Since I had drained the system when working on a hose I had suspected an air lock but had run the engine and added water several times and assumed it had been fixed but NO. Pulled the thermostat and the block was empty. $#!#$&*$!!!!

While I was at it I tested the thermostat and it's good.

So the problem was a result of several things. First a small leak that required adding a little water ever 2-3 hours. Then the air lock that required adding a lot of water every time I ran the engine but never completely filled the water system making it look like I was losing a lot of water.

So some of the things learned. The pressure tester was very useful and a free loaner from Autozone. Combined with the UV additive in the water is GREAT. The UV shows up leaks like a spotlight and is cheap. About $20 for a bottle of stuff and the UV penlight. Finally, pull a hose or thermostat or something to refill the block anytime you drain the cooling system.

I'm 95% certain I've fixed the problem but will do a couple of trips up the river to confirm.

And again, thanks to all for the help.

[skipmac]

Originally Posted by dbraymer

I did not read the whole thread, but pressure testing is DIY and very cheap. You can do it with a bicycle pump. Just pressurize the cooling side with the engine cool and still. If you have a head gasket leak, water will probably enter the exhaust system, or a cylinder.

I had a 4-154 and I was losing water, and it turned out that a cross over tube had a low point leak thru (pin hole), not a head gasket leak. The leak thru stopped when the engine was not hot and running, so it was difficult to find the leak, but pressure testing showed a drip with the engine not running.

If the test ends up showing water dripping out of the exhaust system raw water entry, it points to the exchanger tube. They can be re-soldered, a new one costs about 800.

The pressure test was very easy DIY but getting the loaner from Autozone made it a lot easier to hook into the system without taking apart stuff, making a connection with barbs and pieces of hose and such. The UV additive I liked a LOT.

[DougR]

Glad to hear you found the problem, and thanks for letting us know.

DougR

[skipmac]

Originally Posted by DougR

Glad to hear you found the problem, and thanks for letting us know.

DougR

Not half as glad as I am..

[Cheechako]

I know that when I had the head off my Perkins, the thermostat would not open when I ran it. The problem was air in the block which wont transfer the heat to the thermostat. I opened the thermostat and filled with hot water to the top, reassembled and it was fine.

[skipmac]

Originally Posted by Cheechako

I know that when I had the head off my Perkins, the thermostat would not open when I ran it. The problem was air in the block which wont transfer the heat to the thermostat. I opened the thermostat and filled with hot water to the top, reassembled and it was fine.

I'm thinking I had the same or very similar problem. Will find out when i put the thermostat back. I tested the engine without the thermostat and was very surprised at how low the temp was, about 120 F even under load.

[Cheechako]

Yeah they run cool without it for sure. It really had me stumped, totally rebuilt head... and the engine is overheating! Block very hot. Some hoses were not that hot. Finally the light went on in my skull!

[model 10]

Lucky you. I hate the smell of anti-freeze but would you have smelled it?

[Icarus]

Fresh water coolant can leak into the exhaust, I had this problem on my ISUZU. The gasket at the heat exchanger header tank had a leak. Check the pot where the the raw water gets injected to, if there is antifreeze coolant present or not.
check the heat exchanger and header gaskets or O rings.

[manu_newport 41]

My engine is loosing coolant
and so far I identified the leek to the shower hot water tank exchanger.
The fresh house hold hotwater tank is loosing coolant in the back corner and not easy to see.
I have not done this yet but I plan to connect the IN and OUT from the engine coulant together with a hose connector bypassing my fresh hot water tank and see if that takes care of the problem
I have no coulant mixed with water coming through the faucet

[skipmac]

Originally Posted by manu_newport 41

My engine is loosing coolant
and so far I identified the leek to the shower hot water tank exchanger.
The fresh house hold hotwater tank is loosing coolant in the back corner and not easy to see.
I have not done this yet but I plan to connect the IN and OUT from the engine coulant together with a hose connector bypassing my fresh hot water tank and see if that takes care of the problem
I have no coulant mixed with water coming through the faucet

Had to do this when I first purchased my boat. The old water heater was a rusty piece of junk. Replaced the hoses with a short loop and no problems.