Sea water back-flow through engine

[Karanga]

I am sailing alongside a guy with a Leopard 38 (I think) powered by newish Westerbeke motors, which have standard heat exchangers and pong-boxes.

He has significant water in his oil. As in grey. Froth on the inside of the oil filler cap. As in when sucking cold oil out via the dipstick tube, the first 100ml or so was clear water!

Both motors!

He also has low compression in #4 cylinder of *both* motors.

His discussion with a mechanic suggested that when the motors are off, during sailing, that the sea water continues to force its way past the impellor of the pump, fills up the pong-boxes and then continues to fill the exhaust system until it reaches the valves. Whereupon it has access to the entire internals of the motor.

Is this really a thing??
Can such a system be *so* poorly designed?
Surely these boats are made to a recipe, so if his system is failing this badly, others may be too?

Gobsmacked...

[NYSail]

If it’s being forced upwards I would wonder if he had a scoop fitting put on facing forward? For power boats this is correct however sail boats have to have these fittings reversed facing aft so water is not being forced up while under sail...... non sailors are unaware of this.

Greg

[Wotname]

I would want to the layout of the exhaust system before making the call about the entry via the impeller - of course the mechanic may have eyeballed the entire exhaust arrangement and thus in a good position to make a judgement.

[Karanga]

Mechanic's diagnosis was over the phone, without seeing the actual boat. He says he has come across this on other (number?) boats.

A few months ago, I checked underwater for blockages in his air-conditioner intake. I don't recall seeing scoops (forward or reverse facing) on any of the intakes.

[Karanga]

Mechanic's diagnosis was over the phone, without seeing the actual boat. He says he has come across this on other (number?) boats.

A few months ago, I checked underwater for blockages in his air-conditioner intake. I don't recall seeing scoops (forward or reverse facing) on any of the intakes.

[JDanielBryant]

The impeller scenario seems highly unlikely for a number of reasons. There will an anti-siphon break in the wet exhaust, usually high up well above the waterline that would prevent this. Also the valves are on top of the engine, again high up. More likely would be perforated oil coolers or head gasket failures. The oil coolers are cheap and not too hard to replace - I would do that first

[NYSail]

Originally Posted by JDanielBryant

The impeller scenario seems highly unlikely for a number of reasons. There will an anti-siphon break in the wet exhaust, usually high up well above the waterline that would prevent this. Also the valves are on top of the engine, again high up. More likely would be perforated oil coolers or head gasket failures. The oil coolers are cheap and not too hard to replace - I would do that first

Anti-siphone is after the engine....... depends water level of engines. Over cranking will cause flooding from the exhaust side. I know he must now but does he have a starting issue??

Greg

[JDanielBryant]

Originally Posted by NYSail

Anti-siphone is after the engine....... depends water level of engines. Over cranking will cause flooding from the exhaust side. I know he must now but does he have a starting issue??

Greg

You’re right, if he filled both mufflers running the starter too long, that would fill raw water back to the valves, but wouldn’t water fill a cylinder (a much bigger problem than raw water in the oil, actually) first? That’s usually how over running a starter trashes an engine...

[roverhi]

Back filling the exhaust and into the engine via an open valve usually only happen on engines that are below the water line. Sometimes it can happen when following seas force water into the exhaust. On a Catamaran doubt that the engines are below the waterline and that water could be back fed by waves.

His problem sounds more like a head gasket or other means of water entry. Head gasket would also explain low compression. The fact that both engines are having problems is a mystery as it's highly doubtful both engines would suffer similar problems at the same time.

[Cheechako]

It certainly CAN happen. It happened to me with a loop in the exhaust that was near engine top, while at the dock! (Wind waves into the exhaust which was partly at water level.)

[a64pilot]

I’m of the opinion that water is getting in through the exhaust.
Even if it were getting by the Impeller its way into the engine is via the exhaust.
I’m going to assume a pong box is a water lift muffler?
If it were a head gasket then it would be coolant and the coolant would be low.
Oil cooler is certainly possible, but both at the same time, on I assume a newish boat?
How about two bad exhaust elbows, more likely than coolers?

I’d change oil and stuff a tennis ball or something in the exhausts to block them and see if it repeats.

Not all boats come with anti siphons, mime didn’t and lived for 29 years without one. Lucky I guess.

[Karanga]

He has had a starting issue. Previous owner installed lithium start batteries. Charging is by way of Balmar 614 regulators and VSR's to charge house batteries , and he doesn't think they ever get to full charge.
So there has been lengthy cranking.

He does have an anti-siphon loop and valve.

He is currently doing multiple oil changes. Plus replacing the lithium with lead.

My diagnosis was for head gasket, and I almost had him buying 2 gasket kits, ripping the heads off, etc...

Now I am learning about a really f*cked-up design of a cooling system that could allow this to happen!!!

[Corrosion-Eng]

Hi Karanga,
I think if such occurrences were common they would create a tidal wave of opinion.


I have seen this before and have isolated then corrected the CAUSE. Before I proceed a loaded question: Is the battery negative connected to the body of the engine?


Best regards,
Corrosion-Eng

[DeepFrz]

Is there an anti siphon valve on the water line after or before the heat exchanger? If not then there needs to be one. If so, is it in working order or possibly plugged with salt?

[Karanga]

The anti-siphon is installed between the gearbox and the heat exchanger exhaust elbow. It appears to be functioning and not blocked with salt crystals, crud etc.

The battery negative IS connected to the motor (from memory).