Solving yacht engine trouble: ‘Water had got in through the filler cap’

Pinning down what caused recurrent yacht engine trouble that affected multiple cruises took patience and perseverance for Justin Morton

A year or so ago I was helping a friend, Monty Halls, bring his boat Sobek, around from Plymouth to Dartmouth.

As we were leaving Plymouth breakwater, the engine died. We quickly bled the fuel system and she started back up again and all seemed well. We put it down to a build-up of air.

The wind was south-westerly, Force 4-5, so we carried on under sail and it was actually a lovely passage.

As we turned to head into the mouth of the River Dart we had the usual dilemma anyone with a dodgy engine faces: do you test it for a while beforehand – but risk using up all of the life it has left in it – or just hope it will work for a shorter period, once you’ve committed to the approach? We went for what we thought was the middle ground and started the engine 100 metres before the river entrance narrowed. We didn’t get very far before the engine died again.

We tried to restart it with the key but after a couple of attempts stopped (to carry on turning it over risks flooding the engine with cooling water). We’d chosen to keep the bigger sails up a bit longer, so with the wind now coming out of the river, it was simple to bear away a little to gain some speed and control.

Our first tack failed as we hadn’t gained enough momentum, so – causing a little alarm to the crew – I bore away towards the rocky shore and gybed around instead.

Although we had to beat, the wind was light and we were at high slack tide. What followed was slow progress up river, desperately trying to make progress on the lifts and tacking in patches of more stable air once we had enough speed.

It became obvious quite quickly that I couldn’t describe what needed to be done with the mainsail to keep the boat moving – crucial to maintain steerage.

So I gave up the helm to another crew mate and I took the mainsheet instead. Monty went forward to rig a line for us to tie up to a buoy (he maintains this is because we wanted him out of the way; I’ll offer that it was because he was the only one of us who knew how to use his new-fangled line-threading boat hook).

It wasn’t long before the outgoing tide started to build, so we gave up hope of getting to the town pontoon and picked up a mooring buoy instead. We quickly found the problem. There was water in the fuel – too much to deal with there and then – so we left the boat and went home.

Solving yacht engine trouble: Fuel polishing

A few days later, she was towed to a marina, and we emptied the tanks and tried to polish the fuel with a home-made fuel polisher to remove the water. It turns out fuel polishing only works if there is a little bit of water in the fuel. Ours was emulsified, and water had overwhelmed all of the filters right up to and beyond the fuel injection pump.

We emptied the tank as much as we could, replaced the fuel with fresh, changed the filters and had an engineer look at everything. She was fine again. Racking our brains, we decided the water had got in through the fuel filler cap in the cockpit floor. Over winter, the cockpit drains had clogged up with leaves and we’d come back one day to a foot of water in the cockpit. This, we surmised, had overwhelmed the fuel cap seal – and that’s how the water had got in.

With the cause identified and the problem solved, we made plans for a summer filming trip along the South Coast and to the Isles of Scilly. All was well until Falmouth when, after two unpleasant stormbound weeks, the engine died as we set off again.

We checked the fuel, and again it was emulsified with water. This time, we got a professional fuel polishing team in, but as before, there was too much water in the fuel to separate it out.

We emptied the tank and replaced it with fresh. But we were stumped – how was the water getting into the fuel? With a busy schedule to meet, we carried on, but from then on, before any significant passage, we’d motor around for half an hour beforehand, tie back up, stop the engine and check the primary fuel filter for water before carrying on.

This method got us to the Scillies and back as far as Plymouth without incident. But in hindsight, the weather had been pretty dry throughout.

A week or so later, preparing to leave Plymouth, the engine didn’t fire on all cylinders for a few seconds but then ran normally. This put us on our guard and while motoring out, we noticed a very light rainbow slick of diesel or oil coming out of the exhaust – not much, but definitely a different symptom.

We watched it for a while as we motored towards the breakwater but felt it was too risky with light winds forecast, and returned to the marina and called SeaStart (for the fourth or fifth time that year). Over the phone, they thought it was likely a problem with an injector, so we didn’t risk moving the boat that day.

Injectors serviced, we set off the following week with better winds and she got us back home to Dartmouth without incident, although we only used the engine to leave the side and tie back up again. She then went into Darthaven Marina for them to have a look.

Diagnosis

It transpired that the fuel filler pipe (changed and moved by a previous owner) had a breatheable filler cap not designed to lie horizontally. Consequently, water seeped into the tank whenever it rained. It also turned out that there was no separate fuel breather pipe, so had the cap stopped the water going in, the engine wouldn’t have worked properly either.

What was remarkable was the engine itself. The Yanmar had come in for some pretty ferocious criticism over the preceding months. Actually it is a testament to how robust it is that it had been running on diesel and water for over a year, largely kept going, and has come out pretty much unscathed.

Since the fuel filler pipe has been moved, water has not got into the tank, and that problem has finally been solved. However, boats being boats, we have now moved on to trying to work out how air still seems to occasionally get in, but hopefully that will be more straightforward to work out!

Article continues below…

Solving yacht engine trouble: Lessons learnt

Consider your options

Consider your options and always plan for what you’ll do if the engine dies.

For sailing boats, it’s usually a choice between dropping the anchor or keeping/starting sailing. I was lucky in that I have been teaching sailors how to sail yachts onto buoys and pontoons for a long time.

What was tricky that day was how fluky the wind was, but with very little current I was pretty confident I could get her upriver, which was our most convenient option. We could have sailed into a nearby anchorage or just dropped the anchor where we were and then tried to tow ourselves in with the tender once the tide had slackened.

The benefits of a ‘Last Parade’

A ‘First Parade’ is what the military would call your pre-start engine checks. A Last Parade is the same checks at the end of the day once you have stopped for the night. The military do this so mechanics can work overnight if an issue is found, but also so that, should you have to leave in a hurry, you know your levels are fine if you can’t stop much the following day.

If you are monitoring an issue (as we were), or think you might have to leave in a hurry (from anchor, for instance), checking your engine (or other systems) at the end of the day will highlight issues early and give you a little more peace of mind.

Check thoroughly and repair things properly

Getting the fuel tank out to give it a proper clean would have been a nightmare. Consequently, we never got all of the contaminated fuel out when we replaced the fuel.

This meant that as soon as we saw a little water, we assumed it was just the dregs of the old fuel and not a continuation of the same problem. Had we been able to say definitively that we still had the problem, we would have been more inclined to reassess our ‘fix’.

Consider if a quick fix really is the right thing

We limped along for months without really getting to the bottom of the issue. We put coping strategies in place, telling ourselves the trip was the most important thing and that we didn’t have the time to really get things checked out.

We were always safe, but consequently, we wouldn’t go anywhere unless there was wind, which ultimately caused us several delays. Take a loss or reduction of any capability seriously.

It’s rare that things fail catastrophically. Often, a small issue will tip the balance when combined with other challenging circumstances. We made sure the engine was only a convenience, not a necessity, but it is feasible that we could have really needed it to work flawlessly at some point – and it couldn’t have been relied upon.

Help the experts narrow down the problem

There are so many things that can go wrong with a boat that experts can sometimes need a hand to focus in.

You will know your boat better than most, so tell them everything you can think of and let them discount what’s irrelevant. Also, don’t leave out any key bits of information that could prompt them to tell you it’s not safe to head out. Experienced sailors are often tempted to do this.

Just because something is there, doesn’t mean it’s right

We made the assumption that because the fuel filler cap had been where it was for a number of years and hadn’t caused any problems we knew of, it was fine. That was just luck.

Owners with differing levels of skill and knowledge will work on their boats themselves with various levels of success. You will likely use the boat differently, and it is usually these changes that cause issues that haven’t been there before.

If you have any concerns, get them checked out. Often it’ll take less than an hour for an expert to check something, and they will likely explain or teach you something while they are doing it.

Note what ‘normal’ looks like and act on any change

Our engine had always smoked, which was previously explained away as ‘sooting’ from battery charging at low load, but what colour it was was always up for debate. This took us on a merry dance, and nowhere was a cause listed as ‘water in the diesel’. However, we got to know what ‘normal for us’ looked and sounded like, and we were always on our guard.

Had we not spotted the very slight oil sheen occasionally coming out of the exhaust that day when leaving Plymouth, we may have set off and ended up drifting for hours with no wind.

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