Avoiding water coming in through exhaust (hydrolock)

[jsc7]

Hydrolock caused by salt water coming into the engine via the tail pipe on inboard engines can be a serious problem, but I do not see too many posts on this sub-forum complaining about that occurring so it must be pretty uncommon.

Typical owner manuals list a range of things that can cause it: drift fishing in heavy seas or in wake-strewn areas, being anchored in heavy seas, backing up over a wake, slowly down or stopping suddenly, an engine shutdown while in motion, hoisting the boat stern high. It would seem to be a lot of opportunity for water to get into the engine, but I don't see the complaints.

I guess the reason why it does not seem to happen much is that the water has to get past a gauntlet of twists and turns and make it through the muffler as well.

Is hydrolock commonly experienced and a constant threat, or something that most boaters with inboard engines don't worry about too much?

[CSY Man]

Had it once on my sailboat.
Cylinders on the 4-108 filled up with sea water, found it early next morning before any damage was done.

[DeepFrz]

There are many threads on CF dealing with hydrolock. Not always referred to by name but look for "water in engine" or similar.

[Badsanta]

Very common, especially when having starting your engine problems. Over cranking fills the exhaust lift muffler with raw water till it backes up into the motor.
I had it happen several times and is an easy fix if cought asap. You can't just fix it next week.
Don't crank the motor over 20-30 seconds without turning off the raw water intake. Be sure to open it as soon as the motor starts.
As stated before, lots of info about this here.

[tkeithlu]

Let's hear it for dry exhausts. Usually louder than wet, but no 4" hole at the stern waterline.

[Lepke]

Originally Posted by tkeithlu

Let's hear it for dry exhausts. Usually louder than wet, but no 4" hole at the stern waterline.

I've run many dry and wet exhaust vessels. Wet is a lot quieter, doesn't spit soot/unburned fuel, and so on. Ships, tugs and boats.

[barnakiel]

I had the dry kind on an Oyster. Was very quiet but maybe because the boat was a huge beast too.

I am not sure the same term applies but it seems it is far more common for water to get thru the elbow (siphon valve fault) or via a faulty head gasket. (?)

b.

[UNCIVILIZED]

Thoughts on how much a flapper on your exhaust exit helps in preventing this? And who has a "failsafe" ball valve which prevents accidental backfilling due to waves, & or storms? Fail safe being in quotes, since if you forget to open said valve once the engine is running, bad events could ensue.

[oldcal46skipper]

After 20+ years rebuilding inboard engines, about half the rebuilds are due to excessive deterioration of the water injection elbow and/or the location of same. I have 3 Yanmars in my shop for rebuilding due corrosion in the elbow obstructing flow, then when the engine is shut down water flows into a cylinder through an open exhaust valve. If the engine is re-started soon enough you maybe okay. If it is a multi cylinder engine and one cylinder has water and another fires POW. Water is virtually in-compressible, so something gives, usually a piston top.

I have one like that on my "AW SH_T" table, plus other items, like water injection elbows. Before I left cruising in 1988, I had a stainless steel elbow made for my Yanmar genset, it now has over 6,000 hours on it. I question the engineering of building exhaust elbows of cast iron... maybe so they can sell you a new one each year?

Tom Vandiver, Cal Cruising 46 SATORI, swallowed the hook in Bayou Chico

[barnakiel]

You do not need any valve. You can simply block the exhaust with a bundled plastic bag. And many exhaust thruhulls have a special flap. They cost the same as plain open thruhulls.

If you forget and leave the bag there, the engine will not start.

Many users make their boats too complex by adding valves selenoids traps and sensors where some common sense would suffice.

A well designed exhaust does not allow sea water in, so probably do not head offshore in a boat that was put together by an ignorant and you might be just fine.

Cheers,
b.

[Cheechako]

I've seen enough of it to think it's not uncommon. There are ways to avoid it. Vacuum breaks, loops near the exit etc.

[Three Sisters]

Originally Posted by jsc7

Hydrolock caused by salt water coming into the engine via the tail pipe on inboard engines can be a serious problem, but I do not see too many posts on this sub-forum complaining about that occurring so it must be pretty uncommon.

Typical owner manuals list a range of things that can cause it: drift fishing in heavy seas or in wake-strewn areas, being anchored in heavy seas, backing up over a wake, slowly down or stopping suddenly, an engine shutdown while in motion, hoisting the boat stern high. It would seem to be a lot of opportunity for water to get into the engine, but I don't see the complaints.

I guess the reason why it does not seem to happen much is that the water has to get past a gauntlet of twists and turns and make it through the muffler as well.

Is hydrolock commonly experienced and a constant threat, or something that most boaters with inboard engines don't worry about too much?

If you are considering gassers, the camshaft profile is an important consideration in that valve openings and duration and LSA do not bring you over the edge into ingestion territory.

Deteriorated risers are another.

[UNCIVILIZED]

I'd say that sometimes valves are needed. Picture running downwind (especially under sail alone) in a Winter North Sea Gale. Those waves have quite a bit of force with which to push water "uphill" into engine plumbing. Non?

[wingless]

The Mercruiser engines in my boat have raw water cooled exhaust manifolds, risers and elbows. When these are used in a salt water environment and they are not periodically inspected and then replaced once deteriorated, the result is engine failure.

My exhaust was redesigned by me from no fresh water flush possible and the bottom half of those expensive cast iron parts filled w/ salt water 24/7/365, to now flushed w/ fresh water, soapy water and Salt Away after each use. Then I drain the exhaust bone dry, ready for the next use.

Additionally, Sea Ray had built prior model years of my boat w/ a water lift muffler. In 2000 they switched to the lower cost log muffler, until many boats suffered hydrolock when quickly coming off throttle and getting whacked in the rear by the boat's wake. Sea Ray reworked my boat and many others to remove the log muffler and to install the water lift muffler, to restore protection from that failure mode.

[Jim Cate]

In 2000 they switched to the lower cost log muffler, until many boats suffered hydrolock when quickly coming off throttle and getting whacked in the rear by the boat's wake.

You sure about this? I don't see how water could be forced up the exhaust with the engine(s) running, especially enough to cause hydro lock.

Jim