The drive system is what carries the engine's power to the water. It affects handling, interior layout, draught and maintenance all at once. On pre-owned motor yachts you will meet four arrangements: shaft, V-drive, pod and sterndrive. None is right for every use.
Shaft drive
With shaft drive the engine sits inside the hull. A shaft runs from the gearbox out through the hull and turns the propeller, and a rudder does the steering. It is a mechanically simple arrangement, and plenty of engineers can service it. The engines usually sit near the middle of the boat.
Maintenance covers the shaft seals and bearings, the propellers, the rudders and the alignment between engine and shaft. Alignment or propeller problems usually show up as vibration on the sea trial. Bow and stern thrusters help when berthing.
V-drive
A V-drive is a shaft arrangement too, and the difference is where the engine sits. It is close to the stern and faces backwards, and a V-shaped gearbox turns the power round and feeds it to the shaft. That frees the middle of the boat from the engine, and a larger cabin or saloon can go there.
The price is paid in the engine room. The engine is fitted into a tight space aft, and on some boats it is hard to reach all the way round it. The gearbox oil and couplings are part of the maintenance.
Pod drive
With pod drive, units connected to the engines go down through the bottom of the hull and turn on their own axes, so they steer the boat as well. Electronic control means berthing can be done with a joystick. The engines sit close to the stern, which leaves room inside for the layout.
Pods are mostly maintained by the manufacturer's authorised service agents, and fewer firms have the tools and training for them than for shaft drive. The boat is hauled out at intervals for the bellows, the seals and the drive oil. The fault records of the electronic control are part of the maintenance too. Ask beforehand whether there is an authorised service agent where the boat will be kept.
Sterndrive
With a sterndrive the engine is inboard and the drive leg comes out through the transom. The leg turns to steer, and the trim setting corrects the boat's attitude under way. This arrangement is found mostly on small and medium-sized boats. It takes up little room, the leg can be raised and it is easy to maintain ashore.
Maintenance covers the bellows, the anodes, the condition of the leg oil and whether any water has got in. On boats that stay afloat for long periods, corrosion needs watching closely.
Which one suits you
If you will be in and out of berths often and run the boat short-handed, easy handling comes first. If you plan long passages in distant areas, the service network and spare parts decide the matter. The maintenance budget, the layout you prefer and the engineers available where you will keep the boat count as well. Not every drive is found at every length, so the drive is chosen together with the length.
What to check in the listing and at the survey
- The type and model of the drive; if the listing doesn't say, we ask the seller's broker
- The date of the last service, where it was done and the records
- The date of the last haul-out and underwater check
- The record of bellows, seals and gaskets being replaced
- Vibration, noise, handling and the behaviour of the controls on the sea trial
- On electronically controlled systems, a read-out of the fault records by the authorised service agent
At the survey the drive system is examined together with the engines, under a heading of its own. If the last underwater check was long ago, a survey with the boat ashore lets the drive units be seen directly.
The drive system decides both how the boat is handled every day and what maintenance it asks for every winter.
