Canal boat engines: daily checks

I suspect it’s safe to say that with modern cars, few people bother to check the oil or water levels unless a light flashes on the dashboard to indicate a problem. You could adopt the same approach to the boat but the last thing you really want is the engine cutting out when you’re half way through a tunnel or going up a river against the current and so on. Thus there are some daily checks that every narrowboater should get used to doing.

1. The stern greaser (inboard engines only!)

Here’s a little mental exercise for you: consider the propeller and the engine. Since when the engine runs it turns the propeller, there must something that connects them. That thing is called the propshaft (propeller shaft). All good so far? Engine -> propshaft -> propeller.

Now bear in mind that the engine is inside the boat whilst the propeller is outside in the water. Therefore there must be a hole in the hull which the propshaft goes through. In that case, why doesn’t all the canal water leak in and sink the boat?!

The answer is that – but don’t panic – it can. Or at least, it could in theory.

In practice, the hole the propshaft goes through is carefully made to be only just big enough for the shaft itself so there’s not a lot of space for any water to come through.

Even so, without something else to stop it, water would dribble into the boat, which would be disastrous.

For this reason, two different mechanisms have been invented to stop the water and one of them needs your daily attention.

The first, generally maintenance-free, system is called a “water lubricated” seal and other than checking it and very occasionally giving it a grease (maybe every few hundred hours of engine running), that’s it. Have a good day.

The second and far more common type uses bit of metal called a stuffing box attached to the hole in the hull (the “stern gland”). Loops of squishy packing material are stuffed (hence the name) into this box, around the propshaft and then generous dollops of lubricant grease squeezed in as well. Nuts on the front of the stuffing box are tightened, not fully, but just enough that the assembly becomes watertight (ish). Over-tightening can result in the propshaft heating up and wearing down over time so don’t overdo it.

The grease performs not only a water sealing function but also lubricates the propshaft as it turns. One of your key tasks each day before setting off (and I strongly recommend from my own experience to also do this again when you moor up) is to squish more grease down there and for this purpose you will find a brass cylinder with a knob on top, usually somewhere in the engine bay not far from the stuffing box.

You turn this just until it feels stiff and that’s it, job done (at least, until the knob is fully wound down which means the cylinder is now empty of grease. At this point you have to unscrew the entire cylinder – just by hand, it won’t be tight – and refill it with a suitable grease)

Take note! Notwithstanding everything I just wrote, the stern gland is still supposed to let the odd drip of water through; if it doesn’t, it’s actually too tight and this can lead to the propshaft overheating and wearing. About three drips per minute as you go along is the right rate. More than that and you either need to tighten the greaser or the nuts on the gland. Less means it’s too tight.

Many boaters casually let the drips accumulate in the engine bilge, only pumping the water out when it gets too high. In my opinion this is appalling as you really don’t want water swilling around in the bilges, rusting the boat from the inside. To that end, I placed a plastic bowl under the stern gland to catch the drips, with a pump in the bowl from which the excess water could be sent back to the canal.

Do not neglect greasing your stern gland if that’s the type you have.

2. Engine oil.

It’s quite likely that an inboard engine will have a gauge on a control panel showing the engine oil pressure or at least alerting you if it’s too low. Outboard engines probably don’t have this but in either case you should spend two minutes checking the oil level on the engine dipstick before you set off.

This is exactly like a car; there’s a long metal stick which pushes into the top or the side of the engine. You take it out, wipe it clean of oil using a paper towel, stick it back in fully so as to dip the end of it in the sump, withdraw it once more and examine the end. There will be marks for ‘low’ and ‘high’ and the oil should come up to somewhere between those marks.

If it’s too low, there will be a filler cap elsewhere on the engine which you can unscrew and add more oil through, being sure to use the correct specification of oil for your engine (many canal boat diesel engines prefer old-school mineral oils rather than the modern synthetics you get in cars)

If it’s too high, someone has added too much! This is a problem and you’ll need to use the technique described in ‘oil changes’ below to bring it down to a more acceptable level.

3. Alternator belt – inboard engines only

Another item worth checking is that your alternator belt is in the Goldilocks zone – not too tight, not too loose but just right. There’s probably a tool to do this scientifically but the more widely-used rule of thumb is to push the belt with your finger in the middle of its longest section and if you can move it about a centimetre then it’s OK.

If the belt’s too tight, it’ll be damaging the bearings in the things it’s attached to (including the water pump, which you don’t want failing else the engine will overheat). If it’s too loose, it won’t be charging your batteries properly, including the engine’s own starter battery, so there may come a day when the engine refuses to turn over. Plus the water pump may not be turned properly in which case the engine could overheat.

4. Diesel Fuel

Canal boats are quite parsimonious with fuel, typically using perhaps 1 to 1.5 litres per hour. On my own boat, which had a 62 gallon tank, I tended only to check it every couple of months as I didn’t move every day and even then tended only to do 3 – 4 hours cruising at a time. It is nonetheless worth just checking there’s enough in there before you undertake any cruising where it would be a disaster if you ran out, such as going through long tunnels, river sections and so on.

The other crucial aspect of fuel to be aware of is ‘diesel bug’. This is an algae which can form in fuel if there’s water in it (such as from condensation inside the fuel tank over winter). Over time, this stuff forms a black gloopy sludge in your fuel tank, which will clog up your engine’s fuel injectors and can be a nightmare.

If that happens, there are specialist companies who will come to your boat and ‘polish’ the fuel, which is to say they run the entire contents of your fuel system through a series of filters to clean out the muck, leaving only pristine diesel. Generally several passes are required.

Prevention being better than cure, it is advisable first to use a bug-preventing additive in the fuel every time you top up (these include “Marine 16” and “Fuel Set”, the latter of which I added to my tank religiously and never had any issues with diesel bug)

Checking for diesel bug before it gets out of hand just requires a long, clear tube with holes at either end; stick it into your tank, right down to the bottom, then stick your thumb over the top hole and withdraw the tube. Because your thumb is over the top, the fuel stays in the tube so you can bring it right out and see if there’s any muck.

5. Weed hatch (inboard engines only)

Not, as the name might suggest, a cunning hiding place for illicit drugs, the weed hatch is a metal plate clamped over a raised section of hull in the engine bay, directly above the propeller. In the event that you get anything trapped around the prop – and believe me, you will – you can clear them through the hatch instead of having to jump in the canal.

Warning! Quite clearly, putting your hand anywhere near the propeller is dangerous if the engine is switched on. For this reason, be absolutely sure to turn it off and remove the key before putting your arm down the weed hatch.

Also, be absolutely sure to fully re-seat and tighten up the weed hatch firmly when you’re done. The motion of the propeller will send water shooting up the hatch so if it’s not shut fully, water will get into your engine bay, which over time could flood it, resulting in engine damage and (worst case) the boat sinking.

Things you might find caught around your propellor include: weeds, plastic bags, fishing line, tyres, mattresses, clothing and so on. Unfortunately, many folk treat the canals as a waste dump. I had to remove a sleeping bag once, which was heavy and very soggy. I also had a lady’s bra wrapped around it going through Birmingham. The wire in that bra made it quite awkward to cut off.

Getting things off is sometimes easy – you pull, they come up – and sometimes an absolute nightmare. Many boaters buy a serrated bread knife not for the galley but for the weed hatch, so they can hack away at offending objects to make them easier to remove.

You’ll largely be doing this by lying in the engine bay and thrusting your arm down the hatch, removing things by feel rather than by sight. Take extreme care not to cut yourself because canal water contains various unpleasant things (not the least of which is animal poo and wee from all the wildlife) and can lead to Weil’s Disease which is extremely unpleasant.

For example, if a length of fishing wire has become wrapped around the propeller and you stick your hand down to take it off, it would be easy to catch your fingers on the fishhook. Very nasty indeed.

Some boaters check the prop through the weed hatch each day before setting off, others wait until they feel the boat is acting oddly and then check. It’s surprising how easy it is to detect something caught once you’re used to how your boat handles in normal use.