What Is A Crankcase?

What Is A Crankcase?

You’d think that owning a boat would be a rather glamorous ordeal, taking you one step closer to the lives of the rich and famous, but it’s true what they say… Boats require constant maintenance.

Boats are constantly bombarded by the elements, causing rapid deterioration to their exposed sections unless we provide the TLC they need.

But equally, if not more, important is taking care of what’s on the inside, primarily, the engine and its components, one of the most important of which is the crankcase.

However, before you can maintain a crankcase, you first need to know what one is and the role it plays in your boat’s primary engine, which is where we come in. In today’s post, we’ll be discussing all things crankcase to ensure you’ll keep your pride and joy purring on and sea-ready.

Crankcases: What Are They?

As implied by the name, a crankcase is a type of enclosure… but not just any enclosure. The crankcase contains the most sensitive components and mechanisms in the entire engine, so it’s absolutely crucial that it’s taken care of to run your boat efficiently.

Why Is The Crankcase Important?

You’ll find the whole crank mechanism, the pistons, the cylinders, and the connecting rods in this single location, and as thermal and lubrication channels have to reach all of these areas, the crankcase itself is the most complex structure in a combustion engine.

In light of this, crankcases are remarkably tricky to manufacture. Very specific alloys must be used, and pouring and cooling times must be mapped out to the second.

Modern versions of this intricate component can only be produced using CAD, as absolute dimensional accuracy is the only way to facilitate proper functioning. So, if it’s left to wrack and ruin, you’ll quickly start to see the detrimental effects on your boat’s performance.

What Does The Crankcase Do?

The crankcase holds all the aforementioned mechanisms in place and allows them to work efficiently.

Now, seeing as the crankshaft, the pistons, the cylinders, and the connecting rods handle everything besides the initial combustion of fuel, the crankcase accommodates most of the engine.

The systems within convert the energy generated by combustion into rotary motion, which is in turn converted into torque before transmission to the propeller. In other words, the crankcase and its constituents take an explosion and turn it into motion.

While this is a relatively easy process to glean, it’s incredibly complex in practice, and just a minor amount of deterioration can cause serious inefficiencies.

Crankcase Maintenance: Oil

Crankcase Maintenance: Oil

The majority of crankcase maintenance revolves around checking oil for various contaminants and changing it in accordance with manufacturer recommendations. Ideally, oil checks should be carried out on a weekly basis.

These checks mostly involve simple lubricating oil water tests to locate possible leaks. Should water content in the oil be below the 2% threshold, the moisture can be weeded out via purification.

If there is more than 2% water in the oil, it’s a sign that something’s wrong and that you’ll need to investigate further, keeping an eye out for cracks.

You’ll also need to check the level and viscosity of the oil, and once every three months, you should send a sample off to a lab to be tested for particulate metal content.

And when inspecting the oil, don’t just use your eyes; have a sniff around and see if you can smell anything akin to rotten eggs. If so, this usually means that the oil is contaminated with bacteria and will need changing ASAP.

Crankcase General Maintenance

While doing your oil checks, there are a few other things to keep an eye out for. First of all, give the surfaces around the grating of the crankcase a look over. Are there any metal particles building up?

This is a sure sign that the metal content in your oil has reached an unacceptable level. Next, inspect the grains themselves. Check for both build-ups and general wear and tear.

Then, spare a moment to assess the web slip marks. Are they aligned? They should be! Check the whole system for dark blue patches.

These are telltale signs of poor lubrication, meaning either oil levels have gotten too low or the quality of the oil has deteriorated to the point it’s no longer doing its job. The cross head is next on your agenda.

Check for any damage, then inspect the cross head guides as well. When it comes to the latter, you’re not just checking for clear damage, but any markings at all, as they’re a typical precursor to damage.

Moving on to the welding plate, keep an eye out for any cracks in the welding, as these are the weakest points in the structure. That said, the plate can be damaged in other ways, so don’t look for welding cracks exclusively.

Now it’s time to give the bearings a once over. If there are any metal particles around, it’s essential that you wipe them away, as they can easily build up and impede bearing performance.

Bearings looking good? Fantastic… What about the piping? Check all connections are secure before moving on to the locking wires and locking washers of the stuffing box. They need to be clean and set firmly in place.

As crankcases can be very different in both size and design from vessel to vessel, never only use a general online guide such as this. Consult the manufacturer’s suggestions to complete any checks that we might have missed here today.

And finally, have a look around to make sure nothing has been left inside the crankcase before ticking maintenance off your to-do list.

Final Thoughts

The crankcase is of utmost importance, no matter what motorized boat you’re sailing on, so be sure to keep it in good condition — Treat it right, and it will treat you right.

When properly maintained, your boat’s crankcase will keep you cutting through the water like a blade — No slowing down, no black smoke, no nasty smells, no suspect clanking or sputtering noises… only smooth sailing!

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