Raw impeller went out, water in cylinder?

[themaniam1]

My impeller went out on my 2000 350 mag merc or so I think. I have had it out alot this fall on the lake and Saturday a Warning alarm went of so quickly glanced at gages and saw that temp was at 185?F so I just turned off the engine. I took the engine cover off and saw that the serp belt was off the impeller so I figured that the impeller went out. I was only a few hundred yards from the marina so I thought I would let the engine cool and then motor into the slip while watching the temp.

The engine would not crank over. The starter would engage and but it felt like it was hydolocked. So I got myself towed in and the boat onto the trailer. Now it is in my driveway and I plan to pull the plugs and then crank it over to clear and water out of the cylinders.

I have been told all the expensive possibilities of a cracked block or cylinder head or head gasket but someone said that they have seen were the impeller goes out and the engine hydolocks. Is that possible? Maybe suck / siphon through exhaust valve? That would be much cheaper for me to fix then a head or block. Oh ya, no water in the crank case or in the valve covers.

Any thoughts would be appreciated. (PS this is my first boat but I do work alot on cars so I understand a GM 350.)

 

[Maclin]

Re: Raw impeller went out, water in cylinder?

Get the plugs out and try to turn it over, the longer you wait the worse it is if water is in any of the cylinders.

The impeller quit turning when the belt came off so it may be ok. The 195 temp is not excessive so you probably did not hurt the engine regarding an overheat.

If you were moving and turned the engine off abruptly then you could have induced a hydrolock.

Get the plugs out and try to turn it over ASAP.

 

[Don S]

Re: Raw impeller went out, water in cylinder?

You should have immediately pulled the plugs, and got the water out of the cylinders. Don't just let it sit in there and rust.
Then spray some oil in the cylinders and crank the engine over. Dry the plugs, put them back in and start the engine for 10 or 15 seconds. Even without the raw water pump or belt hooked up.
Then, worry about the pump and impeller, and putting the belt back on.

 

[joncrisler]

Re: Raw impeller went out, water in cylinder?

Yes, this exact thing happened to me- impeller went out, i quickly shut the motor down, and it injested water into 2 cylinders. I am not exactly sure how this happens, perhaps the engine ran backwards 1 or 2 revs, or the sudden comming off of plane with the engine off pushed water into the exhaust. Regardless, get the water out, fog the cylinders, replace the impeller / belt / whatever. If you in any way suspect a bad exhaust manifold, remove it and check it out.

 

[themaniam1]

Re: Raw impeller went out, water in cylinder?

I pulled the plugs and had water in three of the cylinders. Turned over the engine and blew out the rest of the water, let it sit for a minute and turned it over again to get any water that was left. Sprayed WD40 into all the cylinders and let sit for a couple of hours and then turned over again. Since I had the plugs out replaced them with new. She fired right up! I then replaced the impeller and stuck a hose on it and run it until it got to operating temp. All looks good. I will take it out for most likely the last time this season this weekend, 27?F at my house this morning! Good thing I left the drop light in the engine compartment on all night.

Yes, this exact thing happened to me- impeller went out, i quickly shut the motor down, and it injested water into 2 cylinders. I am not exactly sure how this happens, perhaps the engine ran backwards 1 or 2 revs, or the sudden comming off of plane with the engine off pushed water into the exhaust.....

My best guess it that when you shut down at a high throttle, not letting it idle down allows it to back siphon through the exhaust and into the cylinders with the exhaust valves open.

 

[Maclin]

Re: Raw impeller went out, water in cylinder?

good news