Two Yanmar 4JH4-AE engines, two SD50 saildrives and a Cummins Onan generator: on myCloud the machinery comes in pairs, and so does every bit of neglect. Here is what we do ourselves, what we hand over to a mechanic, and how we always know where each engine stands.
The manual is the reference, not the dock
Everyone has an opinion about the ideal oil-change interval or the best oil. We give no figures here: intervals, oil grades, torque settings and part numbers are in the Yanmar operation manual and workshop manual for your specific engine and saildrive. Keep a paper copy aboard and a digital copy elsewhere. Write down, once and for all, the exact model of each engine and each saildrive leg: it is the first thing any parts supplier asks.
What we do ourselves
Checks before every departure
- Engine oil and coolant levels, with the engine cold.
- Belt condition and tension.
- Fuel pre-filter bowl: any water or sediment.
- On starting, cooling water flow at the exhaust, on both sides.
- A look around the compartment: traces of oil, diesel or coolant, weeping hose clamps.
Five minutes per engine. On a catamaran, it is tempting to start up and go, since there is always the other engine if one falters. That is exactly the reasoning that lets a problem settle in on one side.
Oil changes and filters
Engine oil and filter, fuel filters, saildrive gear oil: all within reach of a careful owner with an extraction pump, rags and a drip tray. Saildrive oil deserves special attention: if it comes out milky or greyish, water is getting in. You do not just change it and hope for the best; you get the leg’s seals checked quickly.
Impellers and anodes
The raw-water pump impeller is a wear part that dislikes both running dry and long periods of inactivity. We keep spare impellers aboard, and when we change one we make sure no vanes are missing: a lost piece usually ends up in the heat exchanger. Saildrive anodes are checked at every haul-out and whenever we dive under the hulls; how fast they wear also says something about the electrical environment of the marina. An anode that suddenly wastes faster than usual is worth investigating.
What we hand over to a mechanic
- Valve clearance adjustment, injectors and the injection pump.
- Replacing the saildrive diaphragm seal, which follows a manufacturer’s schedule and means hauling the boat out.
- Leg seals and anything to do with watertightness below the waterline.
- Diagnosing persistent overheating, unusual smoke or loss of power.
- Engine alignment and mounts. On myCloud, the engine mounts were rebuilt by a composite yard in April 2025, along with the bows and transoms.
Our rule is simple: as soon as a job involves sealing below the waterline, calls for special tools or means opening up the engine, we call a professional. An hour of diagnosis costs less than dismantling things at random.
Engine hours: the figure everyone forgets to write down
The port and starboard hour meters do not necessarily climb at the same pace, and the generator leads its own life: ours read around 1,600 hours in 2026. Without a reading at every job, there is no way to know when the next oil change is due, nor to show a future buyer that servicing was done on time. So for every job we note the date, which engine, the hours on the meter, what was done and which parts were used. Over time, those lines also reveal trends: an engine that needs topping up with oil more often between changes, or an impeller that wears out faster on one side, is telling you something worth hearing.
A real example: the generator space
myCloud’s Cummins Onan generator sits under the teak cockpit floor. Access is awkward, and the temptation to put off checks is real. During the refit, the whole generator space was re-glassed and repainted. As a result, a drip or a rust stain now shows at first glance, and a quick inspection has become a habit. While working in the aft compartments, we also freed up and restored the steering cables and sheaves, which had seized with rust: a reminder that machinery does not stop at the engine.
Keeping a record that is actually useful
In the myCloud boat management app, each engine, each saildrive and the generator has its own equipment record, with its jobs, the hours logged and the manual attached. Scheduled maintenance sends the reminders, and the parts and stock module shows how many filters, impellers and anodes are left aboard before you head out.
In the logbook. One line per job: date, engine, hours, work done, parts. It is short, but it is what lets you answer a mechanic’s or a buyer’s question without hesitating.