Mercuiser Hydro-lock

Malibu496

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97 Mercruiser 5.7, Alpha 2 outdrive, went to winterize the boat and it would not turn over. Figured it was the starter again cause it has done this once before and the starter was the issue from what I could tell then.. Boat sat over night during the first 30 degree night.. pulled plugs and 3/4 cylinders were full of water. Cranked motor over and pumped all the water out. Plugs got wet when it shot water out of the cylinders.. tried to dry then best I could without compressed air.. install them and it won't start and run. Tries to but won't fire up and run.. do I have a junk motor now? Or is it worth it to buy a new set of plugs and try it. Oil wasn't milky but appeared to be higher than when I left it...
 

Scott Danforth

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How long has the motor been sitting full of water.

If more than a day or two, pull the motor apart

If less than a day or two - change oil, get motor running ASAP. Then pull your manifolds and risers and replace them.
 

HT32BSX115

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97 Mercruiser 5.7, Alpha 2 outdrive, went to winterize the boat and it would not turn over. Figured it was the starter again cause it has done this once before and the starter was the issue from what I could tell then.. Boat sat over night during the first 30 degree night.. pulled plugs and 3/4 cylinders were full of water. Cranked motor over and pumped all the water out.

Is this a salt water engine? when were the risers and manifolds replaced/checked last?

How long had the boat sat idle since the last operation (prior to the hydrolock) ?

If the oil is higher, it's likely that there is water in the bottom of the pan. It's not "milky" because it hasn't been run enough to emulsify (mix with water) the oil.

Plugs got wet when it shot water out of the cylinders.. tried to dry then best I could without compressed air.. install them and it won't start and run. Tries to but won't fire up and run.. do I have a junk motor now? Or is it worth it to buy a new set of plugs and try it. Oil wasn't milky but appeared to be higher than when I left it...
Either used compressed air, stick them in the oven or use a hair dryer/heat gun to dry the plugs or replace them.

But you need to find where the water came from. It's probably a cracked manifold/riser, or a failed riser gasket. I would start there if you haven't checked the manifolds/risers and/or gaskets in the last few years. Looking inside the manifold ports, you'll see evidence of water in the ports associated with the cyls with water.........


Regards,

Rick
 

Malibu496

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I don't know how long the water has been in the cylinders. The last time I had this lake boat out was the middle of September. I have not checked any of the manifold parts or risers. I'm new to marine mechanic-ing... I think I will buy a new set of plugs and see if it will still run..I drained the manifolds, and the block through their respective drains.. and neither show any oil just water. by manifold or rider your talking in the exhaust manifolds right?
 

Bondo

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by manifold or rider your talking in the exhaust manifolds right?

Ayuh,..... Where the manifold meets the riser is a gasket, if that fails, water is dumped into the cylinders when ya shut the motor off,...

Could rain water have leaked down through the carb,..??
 

wrench 3

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I'd oil up the cylinders before you try and start it. Squirt engine oil in through the spark plug holes, crank the engine over with the spark plugs out and the coil wire grounded, then install the dry spark plugs. Do this before it sits any longer.
 

Scott Danforth

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If it's been sitting since September, I would be pulling the motor, and then pulling it apart
 

KJM

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Was the engine working good the last time you used it? I would dry those cylinders and get some oil on them and then find out where the water came from. Likely its the exhaust manifolds and/or riser. Starting the motor without fixing the problem won't solve anything and might do more damage.
 

Malibu496

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It's ran flawlessly, besides the carb needing a rebuild causeing a small vacuum leak affecting idle sometimes. I already pulled the plugs and oiled the cylinders till I can get some fresh plugs.. also opened all the drains to coolant system to hopefully prevent any further damage since I haven't been able to pump antifreeze in it because it hasn't ran. Thank you for the responses. I will look into the riser gaskets.
 

HT32BSX115

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I don't know how long the water has been in the cylinders. The last time I had this lake boat out was the middle of September.

That's likely how long you've had water sitting on top of pistons.

You can certainly try running it though You really need to run it long and hard enough to "DRY" (evaporate) ALL the water out of the oil pan and crank-case........ That would mean running it at normal temp at high power settings. (neutral on "muffs" probably wouldn't "cut it")

You could only do that at a lake. And it wouldn't be a bad idea. Otherwise, sitting all winter with residual water vapor present in the crankcase will result in internal rust on the exposed metal inside like the camshaft and rods etc.
 

Malibu496

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Ok thanks guys.. I appreciate the input. I'll report back when I find out if it'll even run again.
 

Malibu496

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Ok drained the block and cleaned the water out over the winter.. forget to add stabilizer to the fuel tho.. 😟 So I fired the boat up.. wouldn't idle.. I assume due to poor fuel..outside the no idle condition the motor ran great.. I've been a mechanic for years.. why do I say this.. cause I've seen many SBC with a blown head gasket.. runs like crap.. ect, ect.. this thing ran fine besides not wanting to run below 2k this time around.. shut motor down.. come back later and pull plugs and I had water in 3,4,6 cylinders which were the only three cylinders who's compression were numbers during my compression test that were skewed.. everything else was right at 200-210 psi and held it.. those other three were 230-50.. but we know the small amount of water affected that.. since then, I replaced the odd side of the motors exhaust elbow and both sides elbow gaskets.. I did the odd side of the motor elbow cause It looked a bit jacked up.. inspection from the outside of the manifolds also didn't find any obvious cracks either... so what's next? The other elbow and both manifolds?
 

Rick Stephens

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Cracked manifolds usually happen on the inside. Also blocks crack inside and then they run fine, except they put water in the oil. Bunch of ways to pressure test just the block, just the manifold or everything at once. Easiest to take it for a long spin and see if the water gets back in the pan. If so, pull the manifolds and use acetone to fill them, it will leak through cracks that water won't go through without heat and or pressure.
 

Malibu496

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Ok thanks! I changed both elbow gaskets and the odd side of the motors elbow cause the old one looked bad.. I fired it back up and I haven't had a chance to go back and see if after I shut it down I still got water in the cylinders this go round.. if so then the manifolds are going to come off and be checked like you said.. and pressure tested if need be.. I would assume the block or heads wouldn't have a leak in em to allow water into the crank case... if it tested perfect during a compression test....? But I'm new to marine applications..
 

Rick Stephens

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Marine or automotive, the major difference is that the cooling system is open, so no pressure, and the exhaust manifolds are double wall and full of water. A crack in a manifold or a bad riser or riser gasket puts water right on your exhaust valves, and into your engine past the rings. Everything else is still just an automotive engine with a few marinized parts.

To pressure test the entire setup you pull the risers off the top of the manifolds and make caps to seal them off. Then pull the water in line off the thermostat housing and make up a way to pressurize from there. 12-15 pounds max. Listen for leaks. That's how you test engine and manifolds together. To test just the engine, pull the water lines off the manifolds and cap em. Then pressurize the engine at the thermostat housing. Test the manifolds separately by capping the water in nipple, setting them level, and filling the water jacket up with acetone from the top.
 

Malibu496

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Awesome thank you! I've only got a couple days to figure this out.. big boat weekend coming up. I'll see what I find and report back thanks again!
 

Malibu496

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Ok just got back to the boat.. and pulled all the plugs and cranked it over.. and I don't have any water in any of the cylinders.. gonna suck the fuel out of the tank and put fresh in and see if I can clear up the engine perf issue it's been having.. and retest maybe at the lake. And I'll advise.
 

Malibu496

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Pulled Carb apart to rebuild it and it looks like it was at the bottom of the lake.. lots of fuel sluge and nastyness.. so this should eleminate the idle problem once back together.. so far no water in the motor either.. found signs of water leaking into it from the top side through the carb.. so that def didn't help diagnosing the origin of the water.. but being out side def didn't help over the winters..🤦🏻‍♂️
 

Malibu496

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It did!! I didn't have any carb dip so I used solvent and soaked it for 24hours before re building it.. got it back together and it fired right up and ran much much better.. only issue with it since then, was about 20-30 mins in on the lake it all of a sudden stopped wanting to idle.. I'm guessing it found another piece of grit and got stuck for a min in the main jet.. cause I opened the idle air a little and reved it up and then it smoothed back out.. no water in the motor either.. we've been enjoying it !! Thanks y'all for the help!
 
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