Overheated then hydro locked

[SATige]

Last weekend my 2002 Merc MPI overheated because the raw water pump locked up. The over temp alarm sounded and I immediately cut the throttle and killed the motor. After replacing the the raw water pump today, I attempted to start it, but it wouldn't crank over. I then began to pull all the plugs, one of the cylinders drained a small amount of water, obviously the reason it wouldn't crank over. After pulling all the plugs and spraying wd40 in each cylinder the engine cranked over smoothly. I then replaced the plugs and after more than usual cranking the engine ran fine and the temp stayed around a normal 175 at idle and would run cooler at higher RPM.

My question; where did the water in the cyleder come from??? Is my engine in trouble? I checked the oil before running the motor and after reaching running temp, thankfully thers no water in the oil. Thanks in advance for your input!

[boatwakes]

Possible the water came in when you killed the motor and then slid to a stop, ask any late 90's sea ray owner about that issue. A couple things you'll need to address immediately: do a compression test, remove the belt and disconnect the two quick disconnect wires on the ignition coil (not the coil wire) and then disconnect the fuel pump power lead located about 6" from the fuel pump mounted on the engine mount. Pay close attention to the cylinder that had water in it and compare readings between all cylinders, they should be within 10%. Nothing should be over 175psi and if it is, there's a liquid source causing the problem as it helps seal the rings during the test. Average for that motor should be 125-150.
Run the motor with 2 cycle oil in the gas at 1 ounce per gallon under load as soon as possible to get the rings clean. If the rings on the cylinder with water have an opportunity to corrode and rust up, they'll stick to the piston and allow combustion blow by into the crankcase. So I guess before I scare you, do the compression test and take the darn thing out this weekend and use the crap out of it then report back.

[SATige]

Boatwakes, Thanks for the reply. First thing I'll do is verify if there is still a water source, that will be evedent when I return to the boat and attempt to start it. I'm still having a hard time grasping how the water can get in there. Thanks again!

[boatwakes]

At any given stop point for the engine, an exhaust valve is open and if you suddenly stop and water slaps up against the back of the boat into the exhaust, there can be enough water pressure to push back up into the exhaust manifold and through the open exhaust valve. There was a class action lawsuit by sea ray owners against Mercruiser for this specific problem because the engines in certain model years were installed with too little exhaust drop from the highest point to the water line. It's called water reversion and can occur on most poorly designed marine exhaust systems. We've replaced more than a few engines in boats because of it.

[Ewok]

I had it happen to my old bayliner because the internal exhaust flap that prevents water from backing up into the exhaust ports of the engine broke and I had water get into the oil. My mechanic took my engine alert and couldn't find a crack in the metal or seals, then finally found the flapper part. Cost me 2500 to have the engine torn apart and put back together but at least it was cleaned up, decked the heads, new seals on everything and ran like a champ afterward, but that mechanic was not so good at his diagnostic skills. If he found the flapper part first it would have been a 600 job instead of 2500

[SATige]

Thanks for the replies guys. The theory of water coming up the exhaust is one I've read about and considered a possibility, I was towing a tube at the time and immediately went to neutral when I heard the alarm. Thinking back I could have at least checked on my riders first...

One other theory I've read about is dieseling due to overheat. What are your thoughts on that? I vaguely remember a puff of smoke come from the engine bay vent after I shut it off. But nothing more than a puff, the air in the engine bay way clear when I opened it up.

Thanks again for the replies, very much appreciated!

[boatwakes]

Dieseling is a condition with carbed motors only. Fuel injected engines shut off the fuel supply and the injectors when the key is off so no extra fuel can make its way into the combustion chamber. If you saw the puff, it was most likely from the cylinder that had the exhaust valve open and the engine shut off when the intake valve and exhaust valve overlap occurred. The water pressure/air pressure of incoming water through the exhaust forced the actual exhaust gas out the intake valve and through the flame arrestor.
BTW, if you have a dieseling problem with a fuel injected engine, you have a stuck fuel injector.

[ddubz]

Possible the water came in when you killed the motor and then slid to a stop, ask any late 90's sea ray owner about that issue. A couple things you'll need to address immediately: do a compression test, remove the belt and disconnect the two quick disconnect wires on the ignition coil (not the coil wire) and then disconnect the fuel pump power lead located about 6" from the fuel pump mounted on the engine mount. Pay close attention to the cylinder that had water in it and compare readings between all cylinders, they should be within 10%. Nothing should be over 175psi and if it is, there's a liquid source causing the problem as it helps seal the rings during the test. Average for that motor should be 125-150.
Run the motor with 2 cycle oil in the gas at 1 ounce per gallon under load as soon as possible to get the rings clean. If the rings on the cylinder with water have an opportunity to corrode and rust up, they'll stick to the piston and allow combustion blow by into the crankcase. So I guess before I scare you, do the compression test and take the darn thing out this weekend and use the crap out of it then report back.

I am not in the business of working on engines, but, is that recommened to use the 2 cycle oil periodically to clean the rings? I have never heard of this and wondering if i should run the boat with this mixture. I do use sea foam a couple times a summer though, will this help with keeping the engine in good shape? ('00 2300v, 6.2 merc)

Great information boatwakes!! Love this site!

[boatwakes]

Seafoam is great for any of the fuel related conditions. Mercruiser, in the manual for fuel injected engines, spells out how to winterize the efi motors using 2 cycle oil because fogging oil may clog the injector tips. 2 cycle oil is really just a rust inhibitor in this instance and helps keep the rings from rusting when exposed to water or when the engine is allowed to sit for a long period of time. You won't have to run in an engine that gets used a lot (50+ hours per year) but I suggested it here to help with the situation of water reversion. When we do valve jobs and cylinder head removals, we mostly use ATF or Amsoil 2 cycle to wipe down the cylinders and rotate the engine to keep the rings rust free while the engine is open.

[mls6722]

After reading this, I am second guessing myself on a decision not to add flappers to my FAE - Here is a write up from FAE on this topic. http://freshairexhaust.us/faedocs/Bo...t_Flappers.pdf

I am interested in thoughts about the risks of running FAE without flappers.

[SATige]

Reporting back. Compression test was good, every cylinder was around 140-150 and no water present. I was surprised to find that the oil was a complete milkshak, last time I check the oil it appeared clean, obviously it wasn't. I did add 2 cycle oil for good measure. Changed the oil and filter and headed to the water. Boat ran great, oil pressure and engine temp all normal. Should it be any suprise that there was water in the oil?

[boatwakes]

YES!!!! Check it again and it'll still be there, you have to flush the motor with multiple oil and filter changes. Oil doesn't milkshake until it's at least 25% contaminated so thats only around a quart but thats a HUGE amount of water to have reverted in one incident.
- Was the raw water pump incident the first run of the season?
- Do you live in an area that freezes over winter and if so, was the boat properly winterized?

[skippabcool]

After reading this, I am second guessing myself on a decision not to add flappers to my FAE - Here is a write up from FAE on this topic. http://freshairexhaust.us/faedocs/Bo...t_Flappers.pdf

I am interested in thoughts about the risks of running FAE without flappers.

I was interested as well since my buddy just got a FAE for his '06 SANTE 210 and Larry said he needed a flapper. I didn't see it but he said that it was needed in his for some reason. I have run mine without flappers for a number of seasons without any issues so far.

[SATige]

It was not the first run of the season, it was the third. The pump shaft failed and the pully about ejected from the housing. I live in south Texas, it does freeze and did this winter. Now I'm worried...

[SATige]

From what I've been reading, it seems that the exhaust manifolds and risers may be a potential source of additional water. Any thoughts on tht would be appreciated. Thanks so much for all of the previous responses.