A powerhead costs many multiples of the pump job. Mercury, Yamaha, Suzuki and Honda, serviced in your slip.
The two symptoms, and what each one means
The tell-tale stream goes weak or disappears. That small jet out the back of the cowling is discharge from the cooling circuit, and it is your only continuous evidence that the pump is moving water. When it weakens or dies, stop.
One caveat: a dead tell-tale is not always a dead pump. The tube is narrow, it scales up with dried salt, and grass at the fitting will block it on an engine whose pump is fine. Clear the tube with a fine wire, run the engine thirty seconds, and watch again — while checking actual block temperature. Stream comes back, you had a blocked tube. It does not, you have a pump.
The overheat alarm sounds. A continuous horn plus an engine that suddenly refuses to rev is usually the ECU protecting the powerhead — Mercury's Engine Guardian and the equivalent strategies on Yamaha, Suzuki and Honda pull power rather than let the block scuff. Do not limp home at speed. BoatUS data puts overheated engines at 4% of assistance calls, clustered in July and August when our water is hottest. Steam, a hot smell, or a powerhead you cannot touch are past the warning stage.
Why Florida saltwater destroys impellers faster than the manual assumes
An impeller is neoprene vanes on a hub, spun inside an offset housing so they flex and pump. Four local conditions attack it.
Sand. Jupiter Inlet, Boynton Inlet and Lake Worth Inlet all move suspended sand, worst on an outgoing tide against a swell. A boat that runs an inlet, idles on a sandbar or works skinny water pulls it through the low-water pickups and into the pump. Sand does not pass through — it scores the housing wall and the stainless wear plate, and a new impeller cannot seal against grooved surfaces. That is why the housing gets replaced, not just the rubber.
Salt. Dissolved solids crystallize inside the pump and in the block's cooling passages, abrading vane tips and reducing flow even when the pump is healthy.
Heat. Surface water here runs into the high 80s in late summer. Hot water cools less and hardens neoprene faster.
Sitting. A parked impeller takes a permanent set in the shape of the housing — the vanes curl and stay curled. A snowbird boat that sat from April to October pumps poorly on the season's first start with almost no hours added, which is why low-hour lift-kept boats still need an annual impeller. September and October are our recommissioning wave for this reason.
Replacement interval: the manual versus reality
| Typical manufacturer guidance | Palm Beach County reality | |
|---|---|---|
| Inspection | Around the 100-hour service | Every 100-hour service, without exception |
| Replacement | Commonly 200–300 hours, or roughly every 3 years | Annually, or every 100–150 hours, whichever comes first |
| After a grounding or sandbar session | Not addressed | Inspect now — sand is already in the pump |
| After a layup of 4+ months | Not addressed | Replace before the first real run |
| After running dry, even briefly | Replace | Replace — 30 seconds without water is enough |
The manufacturer's number is not wrong. It is written for average water, temperature and sediment. Keep a boat at The Bluffs Marina or anywhere else running Jupiter Inlet and you are not in average conditions.
What actually gets replaced
The gearcase comes off to reach the pump. Once it is down:
- Impeller, OEM, with the drive key inspected and fitted
- Pump housing and stainless liner — replaced, not reused; a scored wall will not seal
- Wear plate and base gaskets
- Driveshaft seals in the pump base, and the base O-ring
- Water tube grommet, which hardens and leaks and is behind plenty of "I did the impeller and it still runs hot" calls
- Gear lube drained and inspected on the way out, refilled, new drain and fill washers
Two details separate a pump job that lasts from one that does not. The impeller goes in lubricated with the specified lubricant or soapy water — never petroleum grease, which attacks neoprene. And the driveshaft splines get the correct grease while the top of the shaft stays clean, because grease trapped in the crankshaft spline can hydraulically stop the gearcase seating fully.
Afterward the engine is run and tell-tale flow, live temperature data and block temperature verified. Photos of the old impeller, the old housing and the part numbers go in the digital service record, emailed and texted before we leave the dock. If the gear lube came out milky, that is a lower unit seal problem and you hear it that day, not next season.
An outboard with no cooling flow does not fail gradually. Cylinder wall temperature climbs, the piston expands faster than the bore, the oil film breaks down, and the skirt scuffs and picks up aluminum from the wall. The result is a scored cylinder, a warped head, a failed head gasket, or a seized powerhead. On a modern 250, a replacement powerhead is a five-figure decision and a repower is bigger.
The economics are not close: a pump job is a few hundred dollars and one dockside visit. Warranty repairs and manufacturer-financed repowers are referred out — we say plainly when a failure belongs somewhere else — but the way never to need that conversation is to change the impeller on Florida's schedule, not the manual's.
Questions people actually ask
My tell-tale is weak but the engine isn't hot. Do I still need a pump? Maybe not. Clear the tell-tale tube with a fine wire first and run the engine again — dried salt blocks that narrow tube regularly on a healthy engine. If the stream returns and block temperature reads normal on live data, you had a blockage. If the stream stays weak, or the temperature reads high, treat it as a pump and stop running the engine.
How long does the job take? Most single-engine pumps are a two-to-three hour dockside job including run-up and temperature verification, done in the water at your slip. It runs longer on high-mount installations or when a mounting bolt has corroded into the housing — which happens on saltwater boats. Request a written estimate for your installation.