A Fix

Cruising is often described as ‘fixing your boat in nice places’ and on Flyer I like to live that adage every day. In San Francisco, our urgent project was to install an improved seawater pressurization line to our shaft seal, to prevent our engine flooding with seawater again as it had to us far offshore the coast of Oregon. This will be another technical post and apologies for its dry nature and poor diagraming. You should expect more from an architect!

The system was originally installed by the previous owner to replace a dramatically ruptured PSS seal that reportedly sprayed seawater all over the engine compartment when it failed! He was very passionate to me in his rejection of the PSS design given this experience, and he chose to replace it with a different system, by a company called Tides Marine.

This seal is different than the PSS seal in that it keeps a seal using a tight fitting and replaceable rubber ring that creates the seal to prevent water from entering the engine compartment. It also requires positively pressurized seawater (red arrows in green line shown above) to the shaft seal, using the engine seawater cooling line when the engine is in operation.

The goal of this seawater system is to keep the shaft seal lubricated and cool when spinning. When the engine is not on and we are sailing, the shaft is not spinning and therefore the seawater is -in theory- static in the seawater line.

On Flyer, the installation of the new shaft seal featured a low-lying pressurized line (green) that appeared to be at, or just above, the boat’s loaded waterline. After inspecting it with Kevin in Newport, it was our hypothesis that the low profile of this line, with no loop or vent in it, could have created a siphon when sailing on starboard tack.

So on that lovely day of sailing, unbeknownst to us, the green seawater line remained pressurized enough to create a back-siphon towards the seawater cooling line, which in turn filled the exhaust elbow and wet-box.

As we kept sailing this siphon didn’t stop, and filled up the wet-box, mixing elbow, and then the engine’s exhaust manifold. The water then made its way in through the cylinders, slowly filling our engine oil pan with salty water… raising the apparent oil level on the dipstick to 150% of it’s maximum. I was either incredibly brilliant or, more likely just plain stupid lucky to have checked our engine oil level that evening, before attempting to restart the engine.

The good news was that we caught the problem in time and were able to save the engine with several sequential oil-changes, ridding the engine of salt water. The other good news was that the fix is a relatively simple one. It turns out that all we needed to do was modify our pressurization (green) line to meet the shaft seal manufacturer’s specification, something that the original installer failed to do.

It was a relief to learn the spec reinforced our hypothesis, and all but guarantees that this was the source of our engine flooding. Our re-designed system would not only add a vented loop (anti-siphon) to the pressurization line, but we would make this new loop as high as possible to ensure a siphon would never occur again.

In this fix, I also replaced the older, barely translucent 3/8” hose with new, clear reinforced hose, to allow us to visually inspect the revised line and ensure the new anti-siphon vent is doing its job when sailing.

Since we were raising this line to form a loop, it was also important to make sure this didn’t depressurize the water supply below the specified 1 gallon/minute required to keep the seal working. Through some testing of various heights emptying the line into a bucket, I found the highest possible elevation for the loop that achieved this specification.

Despite some long searches, I failed to find an antisiphon loop/valve for a 3/8” hose. The smallest I could find was 1/2”, and I even had one as spare already on board. But if I used the loop as designed and mated the 3/8” hose on either end, the water supply line would experience a further pressurization drop due to the increased cross-sectional area of the wider diameter loop. To mitigate this, I used a T fitting to allow the vent to join the loop at its high-point, effectively using it as a dead-end one-way valve for the system by adding an end cap fitting to the black vented loop component.

This is by no means an elegant solution but for now it’s doing the job, with a few hundred miles of sailing to prove it. I’m hoping to find a better vent option for the longer term, so please send me any thoughts if you have them!

The lessons learned here are many:

1. When buying a boat, do not assume that mission-critical systems have been installed correctly. In this case I had assumed that the previous owner had installed the shaft-seal system to specification and had initially overlooked it when trying to diagnose a source of the water intrusion.
2. Bring fresh eyes to every problem. We were wandering down the dock in Newport, still uncertain of the seawater source in our oil, when I mentioned to our new friend Kevin that I’d appreciate his mechanic eyes for a few moments. That 15 minutes with him in our engine compartment was invaluable. Thank you Kevin.
3. When sailing in sporty conditions, particularly offshore when boat heel and pitch can be more extreme, always check your engine oil before starting the engine. You just might just save yourself an engine re-build.
4. When sailing offshore always have at least 5 changes of oil (and required filters) on board. You just might need to flush seawater out of your engine.
5. Maintain good humor and flexibility. I am indebted to my patient and understanding crew for the quick pivot to head to Newport and all that detour entailed. Flyer is better off for it and you helped it become part of the adventure and not an ordeal!

After almost three years of stewardship of Flyer, we are continuing to learn more about her every day, attempting to stay ahead of the multitude of boat maintenance and repair projects. And I’m trying to keep my expectations reasonable (or low!) and remain flexible for whatever fate has in store for us. As my mother always says, “He That Expecteth Nothing Shall Not Be Disappointed.”