hydro lock

[fourwinded]

1991 3.0l O.M.C.. ..Three weeks ago I pulled the boat out to summerize it,fired up with no problems,also I noticed the oil was a bit milky.The boat has not been in the water yet.So,changed the oil,hooked up the ears,turned water on and tried to fire it.Found that engine will not crank.I remover all the spark plugs and found #4 cylinder had hydro locked from water(only #4 seems to be affected)also rattling noise heard from exhaust.(think it might be the exhaust flapper)Could this have just been caused by allowing the water to run with the engine off?Could it have come back through the flapper valve?Or do I have a more serious problem.

 

[HT32BSX115]

Re: hydro lock

1991 3.0l O.M.C.. ..Three weeks ago I pulled the boat out to summerize it,fired up with no problems,also I noticed the oil was a bit milky.The boat has not been in the water yet.So,changed the oil,hooked up the ears,turned water on and tried to fire it.Found that engine will not crank.I remover all the spark plugs and found #4 cylinder had hydro locked from water(only #4 seems to be affected)also rattling noise heard from exhaust.(think it might be the exhaust flapper)Could this have just been caused by allowing the water to run with the engine off?Could it have come back through the flapper valve?Or do I have a more serious problem.

Howdy,

Your above post reveals a couple of things.

1. Your milky oil (even before running it) indicates that you didn't change it prior to winterizing.

2. Water in a cyl after shutting down indicates a manifold and/or riser leak, or riser gasket leak. It was only 1 cyl that had water in it because only 1 exhaust valve was open after you shut it down.

3. milky oil indicates a possible cracked head, block, bad head gasket etc.... Water usually doesn't get to the oil by running into an open exhaust valve.....you don't get a lot past the rings......

I would start by removing the riser and inspecting the gasket surfaces.

You may have a bad shutter (flapper) but that usually won't cause "muff" water to get back into the manifold. (although you could have the shutter remnants at the bottom of the exhaust tube clogging it and causing it to fill up.

You can test that by putting the hose in the exhaust tube (after removing the riser) and see if it fills up with max flow from the hose.

You might have a cracked/rusted thru manifold or riser.....


I'd also pull the manifold and closely inspect the block.



Cheers,


Rick

 

[fourwinded]

Re: hydro lock

Hi,you are right the oil was not changed at the end of last year.As for the milky oil,some history .The flapper valve was replace midway through last season and oil was changed then.I think the milky oil may very well just have been caused by what was left in the engine after repair.(bill only states 1 oil filter and 4l oil).
Although it seems to me that the rattle noise is comming from the exhaust riser area.I'll pull riser late and check thanks.

 

[fourwinded]

Re: hydro lock

Forgot to mention,after cranking the engine to remove the water,I reinstalled the plugs.started the engine and then turned on the water(worry about the impeller later).Motor ran fine except for the rattling noise.

 

[HT32BSX115]

Re: hydro lock

Anytime you have water in the oil it's difficult to get all out if you cannot drain it from the bottom. The oil suckers usually leave some in the bottom of the pan.

You may have to change the oil a few times to get it all.

Using a light oil will emulsify the oil a little quicker .....something like a 5w20 etc.....Some people even use a quart or so of diesel fuel in the oil to loosen it up and mix/emulsify the water/oil quickly.

 

[fourwinded]

Re: hydro lock

o.k. after being so discouraged in this boat,I have been running only my other boat this summer.Well today I started looking into the the reason for the hyro lock.I found that the prev. repair to the exhaust flapper valve was a bit hum....
redneckish.(sorry no offense)The valve was homemade,doesn't fit properly and when I saw it,it was jammed almost completely closed position,and off the pin on one side.So I'm guessing that is the reason for water into the cylinder after engine off and water still running.(hooked up to ears).Any opinions would be great.I'll do compression test before re-installing plugs.

 

[bigskiohio]

Re: hydro lock

i hydro locked in the driveway by just running water and not engine you can have small leaks in and still be good, mercruiser even says so because when engine is running exhaust pressure keeps water out. Mine runs great i just wont run it on muffs unless engine is running, i start water as soon as it hits lower unit i start my engine. I dont have a flapper in mine no problems my merc mech says thousands out there like that. he says he hardly ever sees a problem from that. He also said biggest danger is when you put the boat in, put it in slow .
Read this bulletin http://www.boatfix.com/merc/Bullet/01/01_13.pdf

 

[fourwinded]

Re: hydro lock

Thanks to all you out there for the responses,this boat made it in the water.
after replaceing the shutter valve,and 2 oil changes.I went to the lake,started running hot so I pulled it out replace the impeller,and running great.