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Hard Starting After Layup
The first start of the season is when a layup’s damage shows up. Nothing was wrong when the boat was parked; the damage happened while it sat.
Is it safe to keep going?
Getting it started is fine. Getting it started and then going straight out is not. Everything that made it hard to start also makes it likely to fail under load an hour offshore.
Run it at the berth, watch temperature and exhaust flow, then sea trial before you rely on it.
One thing to establish first
If the engine is hard to turn rather than just reluctant to fire, stop. Water can siphon into a cylinder through the exhaust while a boat sits, especially with a marginal exhaust installation. Cranking against it bends rods.
Likely causes, ranked
| Cause | How common | Confirms it |
|---|---|---|
| Flat or sulphated batteries | Very common | Load test |
| Degraded fuel, or water in the tank | Very common | Tank bottom sample |
| Blocked filters from stirred-up sludge | Very common | Filter bowl |
| Air drawn in through a dried seal | Common | Bleeding fixes it |
| Impeller set hard against the cam | Common | No water at exhaust after start |
| Corroded connections | Common | Voltage drop |
| Rodent damage to wiring | Occasional | Visible in the engine bay |
| Water in a cylinder via the exhaust | Occasional | Engine hard to turn |
Fuel and batteries account for most of it. Both degrade with time rather than use, which is exactly what a layup provides.
Diesel bug in the fuel tank · Fuel polishing and tank cleaning
What you can check yourself
Before turning the key at all:
- Every bung, plug and seal fitted during layup is out — especially the exhaust. Running an engine with a blocked exhaust does immediate damage.
- Seacocks open
- Batteries load tested, not just voltage checked
- Fuel filters changed and the separator drained
- Belts and hoses checked for perishing
- Engine bay checked for rodent damage
Then start, and confirm water at the exhaust within seconds.
When to call a mechanic
If the tank has sat untreated, if the engine is hard to turn, or if it starts badly and runs rough. A recommissioning service is cheaper than the tow that follows skipping it.
What marine engine work costs in Australia
Common on these engines
Every engine that sits. Most pronounced on yacht auxiliaries and on southern boats with a genuine winter layup.
→ Winterisation and seasonal layup · Yanmar: hard starting after layup · Beta Marine: hard starting after layup
Frequently asked questions
Why does this happen every season? Because the causes are time-based, not use-based. Proper layup in autumn prevents most of it.
Should I have laid the boat up differently? Full treated tank, clean oil in before it sits, batteries on a maintainer and the impeller relieved covers most of it.
My engine started but overheated straight away — why? The impeller took a set, or the strainer or seacock is blocked or closed. Shut down.
Is it worth paying for a recommissioning service? For a boat that sat months, yes. It finds the failures at the dock instead of at the heads.
Practical summary
Use this fault guide safely
Stop now
Shut down for oil-pressure alarms, overheating, fuel spray, smoke in the engine space or loss of cooling-water flow.
Check safely
Start with visible leaks, strainers, fluid levels, alarms and loose connections—only when the machinery is safe and isolated.
Record evidence
Note rpm, temperature, smoke colour, alarm text, sea state and exactly when the symptom began.
Escalate
Give the evidence and engine model to a qualified marine mechanic; avoid repeated restart attempts.
Sources and verification
This page provides general Australian guidance. The current manual for the exact engine, gearbox or drive remains the authority for procedures, specifications and service intervals.
- 1Battery bank
- 2Isolation & fuses
- 3Starter circuit
- 4Alternator
- 5Panel & alarms