Water in all cyl of 5.0L Chev OMC Cobra GL

[MBCEL]

The engine was over heated when the raw water line came off, the engine was cooled off and the line hooked back up. Boat ran good for the rest of the day. The next time out started and ran fine for a short time. When it was shut off it would not restart, it was like the battery was dead. When we pulled the spark plugs we found water in all the holes both sides. Pulled the exaust manifolds and could find no cracks when we filled them with water on the bench. Pulled the heads and gaskets looked ok, and did not see any visable cracks in the heads or on the block deck. Have not pulled the pistons yet, wondering if there is a way water can be traped in the exaust and come back in to the engine, any help would be apreciated. Boat is a 1997 Glastron w/ 305 chev carb. 220 hp SX Cobra, thanks in advance.

 

[HT32BSX115]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

Howdy,

It sure sounds an awful lot like a reversion event. Did you shut it off while under way?

Also if you have any leaks in the riser/elbow gaskets water can get back into the engine via open exhaust valves. It might not be ALL cyls though......only the ones that had open exhaust valves after you shut it off. But if the whole exhaust system was flooded with water you could get water in the other cyls cranking it... I would check the riser gaskets, risers, manifolds, and the "flappers". in the Y-tube. (I'm assuming that you did not have a wave come over the transom or something....!!)

 

[MBCEL]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

The engine was shut down ahile sitting still, what do the flapers do and where are they located? Thanks again.

 

[Coors]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

Like HT said- a sudden shut off, with wake/ waves behind, will put water in the cylinders.

 

[HT32BSX115]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

The engine was shut down ahile sitting still, what do the flapers do and where are they located? Thanks again.

#51 in the picture below (1 in each side of the Y-pipe).....they don't call them "flappers" but they basically help prevent water from coming back up into the exhaust system after shutdown.

 

[billbayliner]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

Here is a link to a Merc service bulletin that Don posted.

I know it is a Merc and the engine in question is OMC but it is a good read and much of it applies.
----------------------------------------

Merc service bulletin on water intrussion.

http://www.boatfix.com/merc/Bullet/01/01_13.pdf

 

[Don S]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

You water has to have come in thru the exhaust, the chances of both sides having crackes in the heads, head gaskets, block, manifolds or risers at the exact same time is almost impossible.
If you didn't have any waves, I would bet money you had to many people & to much weight on the back of the boat and the riser heights were lower than the outside water line. If that happens, the manifolds exhaust port will fill with water. Even the best shutters in the world won't help when that happens, they (shutters) do not seal of the exhaust completely, only slowing down a wave from behind.

 

[Coors]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

The engine was shut down ahile sitting still, what do the flapers do and where are they located?

Maybe this is my problem- with firefox, I can't see the original statement; onlly the quote.

inversion is the bet here.

 

[HT32BSX115]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

Uh...aren't you seeing the picture above? The "flappers" are in the Y-tube.....#50.

I'm using Firefox too....running in Linux. Works good and lasts a long time.....



The flappers are basically "check valves" that are closed with gravity........... They open with exhaust pressure.

When the engine is off, they're closed (sorta) so when water comes up the tube they impede the flow into the manifolds....they DO NOT seal perfectly... If you had a lot of weight in the back and the wave was big they might still allow some water to get in.

 

[Coors]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

I see the pic, but it's like I can't get several posts in between.
let me loosen firefox rules..

 

[HT32BSX115]

Re: Water in all cyl of 5.0L Chev OMC Cobra GL

That's pretty strange. If you're running the "No Script" extension, you might need to click the set up and allow some the scripts that it blocks....

I use it and I have to configure it for a lot of sites.