Mercruiser 5.7 water in cylinders, I'm stumped, Need direction Hydrolocked

[flukin2601]

Hi all, been a long time follower but could never find the time to sit down and type until now. Thank you for your info, help, and reply's, I hope to try to contribute back to help make the board successful. Here's what I have:

Mercruiser 5.7 Mag/MPI 350 Serial # 1A040331 with B3
2007 with 780 hrs. 250 were Fresh (prev owner), and the last 530 were in Salt
Boat is always trailered, ALWAYS flushed with fresh water and salt-away after every use.
I am the backyard DIYer and do the winterizations & tune ups, maintenance.

Problem: Had the boat out several times this season. 2 weeks ago, day out on water ran good, came home put on muffs, boat ran very rough and stalled. Pulled plugs and found water in all of starboard side, port side was completely dry. After some head scratching, decided it was over my DIY capacity and took to marina shop ( i was thinking it could be a head gasket) .

Compression : 8 - 150 7- 150
6 - 200 5 - 195
4 - 180 3 - 190
2 - 200 1 - 180

Shop advises we replace exhaust, risers, and gaskets. Rust was around exhaust manifolds on heads and riser. Rust was very prevalent inside starboard riser. Inside starboard exhaust, there was rust and an obvious water line? I agree to replace both risers and manifolds. I also had an oil leak in bilge which I could see was leaking from the rubber tube at bottom of pan, it was alot but I kept the oil level by continually adding oil (stupid, stupid...I know). Further inspection at shop showed flaking of rust under pan. Shop advises to pull motor and replace pan. Agreed and Done. Oil had minimal creamy oil when drained, I had done this prior to taking to shop. The pan showed maybe a teaspoon of the milky oil in pan. However when inspecting the pan, there was a blister inside, picked at it and found 3 pin holes. In my ownership of this boat, yes I have had water in bilge and my winterization could of been suspect, yet the boat ran good for 8 or so times this season (but did burn more fuel than usual). Shop also replaces exhaust flappers which were limp, agree and done. Engine reassembled and started up and ran ok out of the boat. Engine then dropped in and buttoned up and ran good at marina ramp in river. This was a very costly marina visit I may say and I have exhausted all my funds for another shop visit. Marina owner gives it a thumbs up and attributes the water to a possible cracked riser, or manifold, or bad gaskets.

3 days ago: Launched and ran for 4-5hrs, engine was 165 temp, on and off several times at sea, drifting but not WOT (too rough seas). Flush at home, no issues. Next day did run hard to 1st spot, 165-167 temp. Turn off, drift for 10 min, then reverse ran rough. Shut off for 5 min, try to restart, engine kinda cranks then starter spins with no crank? Hydrolocked is what I believe happened. Get a tow in, next day remove plugs on STARBOARD side, 4 & 8 have water pouring out and 2 & 6 are soaked. Port side is completely dry. Oil level from dipstick seems ok.

Question: With one side that has water, the other none could this be a head gasket, cracked intake manifold, cracked head, or pin hole in head? If it is any of these, what would be my next course of action? TY in Advance

 

[Lou C]

A rotted hole in the intake would put water in both sides. Water on one side only, would be exhaust (but you fixed that), a blown head gasket or cracked head. I would remove the manifold+elbow on that side, keep them together. Then test the manifold/elbow by propping it up level and hooking your hose up to the water feed hose. Run it for a while and let it sit. See if you see any water running down in the center exhaust passages. This will tell you if the mani-to-elbow gasket is sealing well. IF not re place the gasket, if no water than you have to go further. There is a way to pressurize the engine cooling passages to find leaks, also I rigged up a running test to find a bad head gasket (do a search on my user name), Basically you disconnect the feed hoses to the manifolds and remove the thermostat. Then re-assemble with a new gasket and clear hoses to the manifolds. If you see water with air bubbles leaving the thermostat housing, afte;r running it a bi to fill the t stat housing and hoses, that is a good sign that combustion gas is getting into the cooling water via either a blown H.G. or cracked head. IF that’s the case then its engine tear down time. I had the same thing, water in #1 but not enough to hydro lock it. Blown HGs both sides and cracked exhaust seats in the center cyls in both heads. But I had a bad overheat 3 years before that so it was not unexpected. Fixed with a set of re-man heads and new Fel Pro gaskets.

 

[Lou C]

Seein as how this is a 2007, this should have the Merc dry joint exhaust, its is supposed to be much less prone to water getting in the exhaust gas chamber....is that what you have?

 

[flukin2601]

Thx Lou C, Yes it is a dry joint elbow, #864591T02. Both elbows, manifolds and gaskets were all replaced with OEM. The most I had temp was +/-200 and it was shut down immediately. I'll definitely look into your post on pressurizing the passages.

If a HG is blown, why would it run good @ shop, good @ ramp, good for 1 day (4-5hrs), then good for 12plus miles (approx 1hr drive), then quit / hydrolock?

I did reverse 10 min before it quit, pushing that water up inside, but I have brand new OEM exhaust flappers? I checked them today and they are springy.

 

[AShipShow]

You mention it was rough seas. The exhaust flappers really only work well when the engine is running because there is exhaust gas being forced out which is enough to keep the water from getting up past the flappers. However, if you look at flappers closely, they don't seal off perfectly. Wondering if big enough waves while floating were enough to get water up in your motor.

 

[HT32BSX115]

Shop advises we replace exhaust, risers, and gaskets.

Howdy, Welcome aboard!

Replacing manifolds and risers would have been my first inclination too. Since that's been done, what kind of boat is this in? Do you have 3-6" extensions between the manifolds and risers?

 

[flukin2601]

Mad Props, thx for quick response. Seas were 4-6ft and were hitting the stern. However following my visit to shop, we ran in on Day 1 @ 10-12kts for 30min or so... fine, I flushed it for 10mins Day 1 on trailer ...fine, ran it for over 1 hr Day 2 approx 12nm fine, then it quit. For that amount of time, any water from the flappers should of been gone? I've ran this boat in 6-8 seas many of times and backed down quite a few with water coming over the stern with no relative issues. Did i get water in bilge? Most certainly, but not in the engine if flappers worked and engine continued to run. I'm still at a loss?

 

[flukin2601]

Howdy, Welcome aboard!

Replacing manifolds and risers would have been my first inclination too. Since that's been done, what kind of boat is this in? Do you have 3-6" extensions between the manifolds and risers?

Thx HT, its a 26ft Striper walkaround/pilothouse, I do not have risers in it. I do not believe the elbows are below the water line and I dont't believe we had more weight or fuel than usual to push us below that line on either day. On both days there wasn't anything different that we usually do, I typically run this boat every week during the summer and maybe a few times in spring and fall. If I loaded up both fishboxes with ice and topped off my tank, and took on an extra guy or 2, then there could be a possibility I slipped under that line and would need those 3-6" risers.

 

[AShipShow]

Wondering if because its an MPI motor with a 2 piece intake manifold if for some reason coolant could be leaking in the intake but only getting to one cylinder bank... One of the more knowledgable guys will have to chime in tho, cuz I'm not very familiar with the MPI motors.

 

[flukin2601]

Open system / sea water cooled, No coolant. I should of mentioned that in my OP.

 

[AShipShow]

Woops, didn't mean to say coolant, believe the intake manifold is the same either way tho.

 

[tpenfield]

I would run a cooling system pressure test at this point. I think it was an assumption that it was the exhaust riser gasket that failed (wrong assumption it appears).

I agree with Lou in that an intake manifold leak would probably distribute water to both sides of the engine. I would suspect something more related strictly to the starboard side (even # cylinders) and at this point it may be the cylinder head, valve guides, or even a head gasket. A cooling system leak test, although difficult to set up with open cooling, is probably the best thing to do at this point.

Maybe give the boat shop that did all the work a 'boat engines for dummies' book or something for all their hard work

 

[flukin2601]

I would run a cooling system pressure test at this point. I think it was an assumption that it was the exhaust riser gasket that failed (wrong assumption it appears).

I agree with Lou in that an intake manifold leak would probably distribute water to both sides of the engine. I would suspect something more related strictly to the starboard side (even # cylinders) and at this point it may be the cylinder head, valve guides, or even a head gasket. A cooling system leak test, although difficult to set up with open cooling, is probably the best thing to do at this point.

Maybe give the boat shop that did all the work a 'boat engines for dummies' book or something for all their hard work

Thank you TPen for your response. ok so if we can narrow this down : that it isolated to starboard side, poss bad head, poss bad valve guides, or a blown head gasket seems to be the consensus. Is this rigged up / make shift leak test a good way of telling me anything we don't know already? I'm looking for this test and how to do , basically I'm pumping in air and using a stethoscope to determine where the leak is? Is this the best way? I'm at a loss here.

 

[Bondo]

Is this rigged up / make shift leak test a good way of telling me anything we don't know already? I'm looking for this test and how to do , basically I'm pumping in air and using a stethoscope to determine where the leak is? Is this the best way? I'm at a loss here.

Ayuh,...... Welcome Aboard,..... Here's the condensed version, as I'm a single digit typist,.....

Drain the water from the block, isolate the motor from the in-comin', water, 'n the exhaust manifolds,.....
Plumb in a air fill point, 'n a pressure gauge,.....
Take out all the spark plugs, open the throttle to Wot, remove the oil fill cap, pull any vents, generally, open any opennin's in the motor, that ain't holdin' back the water/ coolin' passages,.....
Apply 'bout 15 psi of air,........ 'n Listen,.......

If/ when ya hear the air escapin' the coolin' passages, follow the sound to the problem,......

 

[Lou C]

What I did was remove the stat, and hoook up hoses to the manifold outlet ports in the thermo housing . Then put funnels in em and taped em up so they stayed straight. Filled with water . Then just ran it enough to warm it up but not overheat the exhaust. Then shut it down. You could clearly see bubbles come up thru those hoses from the combustion gas leaking into the water.

 

[tank1949]

A rotted hole in the intake would put water in both sides. Water on one side only, would be exhaust (but you fixed that), a blown head gasket or cracked head. I would remove the manifold+elbow on that side, keep them together. Then test the manifold/elbow by propping it up level and hooking your hose up to the water feed hose. Run it for a while and let it sit. See if you see any water running down in the center exhaust passages. This will tell you if the mani-to-elbow gasket is sealing well. IF not re place the gasket, if no water than you have to go further. There is a way to pressurize the engine cooling passages to find leaks, also I rigged up a running test to find a bad head gasket (do a search on my user name), Basically you disconnect the feed hoses to the manifolds and remove the thermostat. Then re-assemble with a new gasket and clear hoses to the manifolds. If you see water with air bubbles leaving the thermostat housing, afte;r running it a bi to fill the t stat housing and hoses, that is a good sign that combustion gas is getting into the cooling water via either a blown H.G. or cracked head. IF that’s the case then its engine tear down time. I had the same thing, water in #1 but not enough to hydro lock it. Blown HGs both sides and cracked exhaust seats in the center cyls in both heads. But I had a bad overheat 3 years before that so it was not unexpected. Fixed with a set of re-man heads and new Fel Pro gaskets.

I had a head's passage way give out one time and dump salt water into piston. 10 year old boat was salt water usage and flushed constantly. BUT? Sea Water in pistons can't come but just from a few sources: intake, exhaust or heads.