Somebody's engine destroyed by wave action in exhaust

[Nonchalant1]

Has anybody ever heard of the below?

Doug

If you use a stern anchor and restrict the boats orientation to the natural wave direction created by wind or current, be aware that any wave 2 - 3' high can pump water backwards up you exhaust system into your exhaust manifold and from there into a cylinder of you engine. The condition is called a "hydrolock". If now you succeed in starting your engine, not knowing you are "hydrolocked", as we did, you will break the piston tie rod and probably put it through the side of your engine. This pumping action can occure any time there is a rocking/pitching action of the boat equal to more than half the height of your exhaust riser, and especially if the wave is at your stern.

In our case it happened while anchored from the bow, when the wind shifted 180 degrees, with 2 - 3' waves hitting us at 45 degrees to our port bow, with no wind to hold us oriented to the wave, and enough tidal current to hold us at our 45 degree angle. Water was pumped backwards up our starboard, down wave, exhaust pipe, over a 2' 6" exhaust riser, and into our 4R cylinder on a V8 engine. Started the next morning with a BANG, and a hole in the side of our engine block. Suggest everyone install flappers to the outboard end of your exhaust, unless you have some other sort of check valve in your exhaust.

Chuck and Claria Gorgen
ODYSSEE
Still in Rimouski, Quebec replacing an engine

 

[GaryNW]

While I have not heard of a case while at anchor, there is no doubt it can occur given the wrong conditions. More common is probably being waked in relatively open moorage-like many guest docks.
My PO ate an engine backing down on a halibut- he was a little vague on the details. May have either shut off the engine or was trolling on one. Solution was to install Vernalifts. You don't see these often on 454's.
I troll on one engine so I am somewhat concerned about a large wake from astern. Do those flappers really work? Seems to me that the bad wake is the one that lifts the transom vs crashing down on the transom. Seems to me that the lifting wave would just open the flapper.
Gary

 

[Brian Degulis]

IMHO You should always roll the engine over with the stop button down. This will almost always prevent major damage from water in a cylinder weather from the exhaust or an internal leak.

Brian

 

[captddis]

I hate to disagree with Brian But if you hit the starter button with liquid in the cylinder, you are going to bend the rod whether it fires or not. Detroit rods bend very easily.
If you suspect water ingestion, the only safe way is to use a wrench to turn the engine over. Dave

 

[Brian Degulis]

Oh stop Dave You love to disagree with me. And yeah you may still bend a rod if you got a lot of water and it gets rolling before the wet piston comes up. But you may not and your not going to send the rod thru the block. What I'm suggesting is that it should be done as normal operating procedure if the engines been sitting any lengh of time. Sure if you suspect you got water bar it over by hand.

But it's to late for you now Dave I'm sending one of my relatives from the wood pile down to see you.

Brian

 

[captddis]

As long as they are driving [ or riding their camel] across the bay, have them bring some fuel!!!!

 

[Brian Degulis]

Are you kidding they will be in the Mercedes custom built with extra head room!!!

Brian

 

[krush]

Both you goons, looks like I may have a free day or two in Florida!

 

[captddis]

If you get to the Tampa/St Pete area let me know.

 

[HattsOff]

So...given that the slip I am looking at has an amazing view...but strong daily wind and waves flowing towards my stern...does anyone know where I can buy 8 inch flappers? 10 phone calls made...the largest I can find is 5 inch.

Oh and I did hear one story: anchoring with one engine on and one off (this was for a good reason but the person telling me the story could not remember what was wrong with one engine) and when backing down onto the anchor they didn't have exhaust pressure from the engine that wasn't running and water flowed up into the engine.

Thank you for your help!

 

[seasalt]

I saw a snake go up my 10" exhaust pipe once. My wife just knew that it was slithering around inside the boat. Lighting off the 6-71 TIB with no muffler solved the problem.

I have heard of water getting into engines from the exhaust especially if they have "in line" mufflers (or none) rather than water lift mufflers.

And as far as turning over the engine if this is suspected...water does not compress.

 

[HattsOff]

Hello again,
So does anyone have exhaust flappers on a 53 MY

We go back in the water today after four months of refit. So happy I can barely contain myself.

The surveyor told the owner of the boat yard he was impressed with the work we have done. It's been a lot of work but we are so happy!

Thank you all for all of your support!

 

[bobk]

For long term storage in a marina where wave action slams the transom, you can fit large rubber pipe plugs or small inflatable rubber balls to keep out the water. I've had mechanics do both when servicing exhaust components.

Bobk

 

[34Hatt]

When I had the old oval bronze one's I made my own with a hinge and piece of fiberglass!

 

[GaryNW]

Wow, old thread reopened. I see I was here 6 years ago. On flappers of big diameter where off-the- shelf are not available- these things are crude at best. Make your own (or have some savvy yard do it). Buy some heavy neophrene sheet-say 1/4 " thick. Reinforce with SS mesh or straps. I would weight the bottom edge heavily-maybe with some bar stock zinks.. Attach to transom above the exhaust (Iguess this is obvious).

My own experience: When I went to 496 Crusaders, I upped exhaust from 4" to 5". I bought the most expensive outlets available (Vetus) because they had these built-in plastic flappers. The concept seemed great and they looked cool. At sea trials on new engines, WOT was dictated. My 496's blew the flappers off immediately. Vetus simply refunded full price after requesting photos. (yup, there is a 5" hole with no flapper.)

So to date I have no protection (don't insert crude jokes). I do have vernalifts, and knowledge (run both engines when backing down or in following sea), but I remain uncomfortable.

Only thing off shelf that looks promissing is a vernalift company check-valve thingy that is fairly large (goes inside boat just before transom outlets. What to do?

Is this why medium/large fishing boats are dry stack?

Gary

 

[bobk]

Re water entering the exhaust, does any one beside me get worried when the guy with the power washer sprays into the exhaust? I have had a couple of respected mechanics tell me it is not a concern. My pipes were upsized by a PO and are extended about one foot in about a 75 degree angle outboard after they exit the transom, run 6-7' to an inline muffler and then a few more feet to the Y collector. 6V92's. 1981 48MY Any thoughts?

Bobk

 

[saltshaker]

I had custom surge tubes on my 46C and the 65C has factory surge tubes. I wouldn't think a little wave action would be an issue. Consider the volume of water that would need to go up hill and into the engines. SF back down hard which is why you see the surge tubes in many.