Tony242

Hi Guys
Im a new member and this id my first post so be gentle

I have a 1985 Formula 242sf with a 5.7 mercruiser. I was out on Sunday just cruising a reef at about 1,500 to 1,750 revs when the engine started misfiring and died. Went to restart but had the dreaded hydraulic lock. Removed plugs on left bank and cylinders were full of sea water. Managed to get the boat started and back to the boat ramp but it died when I pulled onto the trailer. I suspected my nice 12 month old stainless risers but I took them off and plugged the hose into them but they don't leak. The boat is fresh water cooled so this is the only place saltwater could get in. I have stripped the motor and the head gaskets are fine and I cant see any cracks anywhere. Am I right in thinking that water shouldn't be able to come back into the exhaust ports at 1,700 revs as the exhaust gas would blow it out the exhaust. The risers are water encased tubular headers. Is it possible that the may only leak when the header tubes are hot and any hole may close up when cold. Pulling my hair out as this is the second engine in 18 months that has ingested water,that is why I put stainless manifolds on. My exhaust flappers are near new as well. The ocean was dead calm so there was no swell coming from behind. When you guys water test headers for leaks do you apply a fair bit of water pressure or is just running the hose through them enough? Sorry for so many questions but I have run out of ideas. The motor is completely stripped now but I am not game to reassemble unless I find a definite cause.

Budman II

Were all 4 cylinders on the same bank full of water, or just one or two of them?

Not sure if I understand your terminology regarding "fresh water cooled". Do you mean that you have closed cooling on it? If not, and you are running it in salt water that is being used to cool the block and heads, then I would suspect that you have developed porosity in a water jacket somewhere. Intake manifold, cylinder head, and the areas around the valve guides are the first places to look. If you had not already disassembled the engine I would have advised you to seal off the water inlets and outlets on the block and pressure test the cooling system. Since you have already crossed that bridge, you will need to closely examine each component and / or pressure test them individually.

I tested my headers with air - made up a jig from steel plate to bolt the exhaust flange to, and then sealed up the outlet, and pressurized the exhaust passages.

Last thing - if you have a valve sticking open or not sealing properly, it could cause enough reversion when the piston goes down in its bore to suck water back up the exhaust into the cylinder.

CDShack

All Budman said, plus a question or two. The second engine in 18 months with water in the motor, would make me think there is weirdness going on. Did you freshen up the old motor or put in a complete new one? All the old accessory stuff? (except exhaust elbow of course)?

The only way for seawater to be NEAR the cylinders is the exhaust, some pretty good reversion, or the heat exchanger for the fresh water system leaking into the system, then a cracked head or blown gasket.. The simplest is usually the right answer.

18 months ago, same side of the motor//same cylinders? "Risers" I am assuming are stainless elbows bolted to the top the exhaust manifold you had already? Same manifold on the motor 18 months ago?

The cast exhaust manifolds HATE salt water!!! Might check the entire manifold itself, leaks, gasket (for elbow) seating, etc. Rusty Pinhole down in it somewhere? I had one years ago did the same thing, you'd run, idle around, and water would blow out and refill, but eventually it would "fill up" enough to drop a cylinder. As RPM builds up, so does water pressure. It's an impeller pump. So as you get the pressure up enough, whatever the defect is will show itself.

Tony242

The cause of the problem 18 months ago was a leaking riser. I didn't pick it up and the boat sat for a couple of weeks with water in the cylinders. The engine had a full rebuild and I fitted full stainless one piece manifolds. I made a typo with the age of the manifolds they were replaced when the engine was rebuilt. When I got the boat home I took the rocker cover off and there was foam inside so I stripped the motor straight away to stop any damage internally. Lots of foam under the inlet manifold and in the valley. I should have thought things through a bit more before I stripped everything but I had just broken down 15 miles out to sea with a fresh rebuilt motor and 2 kids in the boat so I was a bit stressed. My son was helping me pull the plugs and get the water out of the motor and he now seems to think that there was a slight red tinge to the water in the cylinders so so it may have been coolant. The head gaskets showed no signs of leakage and the face of the heads have no signs of cracks. No signs of cracks in the Block. I have to go away for 2 weeks working so I will have to ponder the possibilities. Are Vortec heads prone to cracking inside the inlet ports? I was so sure it was salt water but my son now has me doubting my own observations. How big would a leak in the exhaust manifold have to be to let water back into the cylinders between 1500 and 1750 revs? With hose pressure and blocking the outlet water ports with bits of rubber I cant get them to leak. Looks like I am going to have a lot of thinking to do while I am away working over the next 2 weeks. When I get back I will get the heads crack tested. I still have the oil I drained out the motor when I got home. I might contact an oil test place and see if they can tell the difference between salt water and coolant in the oil. Unless I find a 100% definite cause its not going back together.

SB

You said you have fresh water cooling. Closed systems use coolant.

Therefore, the red he/you saw (with fresh water cooling) is rusty water.

mike tkach

my guess is the salt water ate through the cooling passages around the valve guides.

Tony242

I use red CAT coolant but I was so sure the water tasted salty. Looks like crack testing the heads when I get home

CDShack

Man, that had to be a harrowing experience! It's all fun and games until that motor goes "duh" in the middle of nowhere!!!

Was going to ask about freezing, but I see you're in Australia. I kind of go from simplest to most obscure:

If we take out salt water, the door opens to a several of other things. Foam inside the engine generally indicates there's water coming in the crank as well. Hydro-lock with crankcase foam is most often a Head gasket, but it can be from water forced past rings.
Dumb stuff like corrosion in the intake crossover could leak into the intake runner and valley.
Cracked cylinder wall into the water jacket from the last incident? I would mic those cylinders anyway, as HL can punch a cylinder wall out. Sometime the leak is just at one cylinder, but the hydro-lock pops the head gasket.

Still can't rule out the exhaust though. Any thing made by 6 yo Chinese kids can leak, missed or pinholed weld, bad joint. There are very few good parts nowadays, even fresh out of the box.

Maybe even the working angles of the new exhausts, exit port location or something just not right. How and where the jacket water enters into the exhaust, running back down the pipe? Could be something stupid like that.

Wish there was a hard and fast answer, but it's going to take some step by step investigation down under! I wouldn't put it back together either until I was SURE I thought I had it figured out. Good Luck and keep us posted. Helps everybody here!

SB

Okay. That ends that confusion. You have closed cooling , not fresh water cooling as you previously stated.

So.......do you have it set up that the ocean cools everything but inside the motor, or do you have coolant going thru your exhause manifolds too, with the sea water just going thru the risers ?

Tony242

My manifolds are salt water cooled and the engine is closed cooling with a heat exchanger. Manifolds are water encased tubular stainless headers with no gaskets apart from the gasket between the head and the manifold. Engine has run 120 hours faultlessly since the rebuild wit quite a bit of hard running involved. When I get back from work I will have the heads crack tested. I suppose a leak in the cylinder walls would be easy ast to spot? No freezing here Iive in the tropics