Personal Watercraft Service on Lake Winnipesaukee

The impeller spins inside a wear ring with a small designed clearance between the blade tips and the ring. That clearance is what makes the pump efficient, because it is what stops water slipping back past the blades instead of being driven out of the nozzle. Sand, gravel and weed passing through cut grooves into the softer ring and nick the leading edges of the blades. The gap opens up gradually and the machine loses thrust without ever feeling like it has broken.

The symptoms are specific and easy to recognise once you know them. The engine revs up to its usual ceiling but the ski will not reach the speed it used to, acceleration out of the hole goes soft, and it cavitates under hard throttle. Owners often start chasing the engine at that point and get nowhere. We measure the blade-to-ring clearance first, because a worn ring is a common and comparatively contained repair, and there is no point tuning an engine around it.

Everything the pump takes in goes past the intake grate first. Weed, fishing line, a plastic bag or a length of rope wraps around the driveshaft behind the impeller, and line is the worst of them because it works its way into the driveshaft seal, cuts it, and lets water into the bearing. Sand picked up in shallow water goes straight through the wear ring and does its damage on the way. None of this is visible from the seat.

On Lake Winnipesaukee the shallow weedy coves and the sandy shallows close to shore are where intakes pick this up. Idling through weed, or riding into a foot of water to load onto a trailer, is enough to do it. If the ski loses thrust suddenly, shut it down rather than trying to power through, because that is the moment debris is being pulled tighter around the shaft. We clear the pump, inspect the seal and check the shaft for scoring.

Flushing after every outing is the single habit that keeps one of these alive, and it matters in fresh water as much as anywhere. The lake brings in weed fragments, sand and silt, and they settle in the cooling passages and the exhaust where they hold moisture against metal for months. Flushing is done to the machine's own procedure and in the right order, because most designs run the engine with the hose connected and must be shut down in a set sequence or water backs up into the exhaust.

These are small, high-revving engines that work hard for their size. Oil changes and spark plugs are the routine work, done to the engine's own service schedule rather than a figure off a chart. Plugs fouled by long idling and short runs are a common cause of a hard start or a rough one, and they are cheap to rule out first. Fuel is worth attention too: pump gasoline runs up to ten per cent ethanol, which draws in water and does a part-full tank no favours.

The freeze risk on a personal watercraft is the water left sitting in the pump, the cooling passages and the exhaust after the last ride of the year. It does not all drain out on its own. Whatever is still in there when the temperature drops expands as it freezes and cracks whatever surrounds it, which on these machines means an exhaust component or a cooling passage. Winterizing clears that water out, stabilises and treats the fuel, and preserves the engine internals to the manufacturer's procedure.

This is not a theoretical risk here the way it is further south. Ice-out on this lake was declared on 13 April in 2026, and the record kept since 1888 runs from 17 March at the earliest to 12 May at the latest. A ski left in an unheated garage or under a cover goes through months well below freezing before any of that. The battery comes out, gets charged and is stored somewhere it will not freeze flat and fail in spring.