How long should I flush the motor before the first start of the season?

Follow the exact engine manual for cooling-water supply, engine position, propeller precautions and permitted run time. Some flushing ports are engine-off only, while other approved procedures require idling. Never assume a hose fitting permits running. At first start, check the specified cooling indication immediately and stop for absent or abnormal flow or warnings.

My motor was properly winterized, can I skip spring commissioning?

No. Proper winterization protects the motor over winter, but commissioning is about checking what happened while it sat. Fuel lines age. Rodents occasionally nest in engine compartments. Electrical connections corrode. Battery voltage drops. Even a well-winterized motor benefits from a visual inspection and a first start using the exact manual's approved cooling-water setup.

When should I change the gear oil on my outboard?

Change gear oil every season or every 100 hours, whichever comes first. Spring commissioning is an ideal time if it wasn't changed at fall winterization. The critical check is for milky oil: milky gear oil means water has entered the lower unit through a damaged seal. If you see milky oil, do not run the motor, get it to a service shop immediately. Harris Boat Works services Mercury and MerCruiser engines.

How do I know if water got in the lower unit of my outboard?

The primary indicator is milky or coffee-coloured gear oil when you remove the drain plug. Normal gear oil is dark amber or reddish. Other signs include grinding noises from the lower unit while in gear, resistance when shifting, or visible rust around the drain plug. If you find milky oil, don't run the motor, bring it in for inspection. Caught early, it's a seal replacement; run it with water in the gear case and you're looking at a full lower-unit rebuild.

How much does professional spring commissioning cost in Ontario?

Ontario shops typically charge $150-$350 CAD. At HBW the spring check is free for our winter storage customers and $99 for everyone else. A basic commissioning is at the lower end; a commissioning that includes gear oil change, spark plug inspection, impeller check, and fuel filter replacement costs more. Harris Boat Works provides an upfront scope before starting, request service at hbwservice.ca.

What's the best time to book spring commissioning near Rice Lake or the Kawarthas?

Book in February or March. By mid-April, most service departments near Rice Lake are fully booked through May. If you're targeting Victoria Day weekend as your first launch, your motor needs to be in the shop at least 3-4 weeks beforehand. Harris Boat Works has been doing spring prep on Rice Lake since 1947, early booking means your boat is done and waiting when the lake opens.

Should I replace the water pump impeller every spring?

You do not need to replace the impeller every spring. Follow the exact manual for the engine; many Mercury schedules place water-pump service at an expanded interval around 300 hours or three years, while model and operating conditions can change it. A weak telltale, reduced water pressure, or overheat warning needs diagnosis sooner.

Can I do spring commissioning myself, or do I need a dealer?

Most of the commissioning checklist is DIY-friendly: battery check, fuel line inspection, propeller inspection and a first start using the exact manual's approved setup, with control checks on the water at idle. Where you need a dealer: EFI diagnostic checks, impeller replacement, fuel injector service, and hydraulic steering work. If you find milky gear oil, unusual start behaviour, or warning alarms, stop and call a dealer. For engine repairs, Harris Boat Works only services Mercury and MerCruiser, call 905-342-2153.

Does ethanol in fuel cause problems during spring start-up?

Yes. Ethanol-blended fuel (E10) can cause issues if it wasn't treated before storage. Ethanol absorbs moisture, and fuel sitting over winter can phase-separate into an ethanol/water layer that won't combust properly and can damage fuel system components. Prevention: use fuel stabilizer at storage, and ideally drain the fuel system before long storage. In spring, if you're starting with old untreated fuel, drain and replace it. Most Mercury EFI four-strokes are rated for E10, do not use E15 or higher.

Spring Outboard Commissioning Checklist (2026 Ontario)

Need your PCOC? Take the online course through HBW's MyBoatCard referral link and use HARRIS15 for 15% off. --- Why This Matters More Than You Think The motor sat for five or six months. Fuel settled. The battery discharged. Rubber components stiffened.

HBW technician inspecting a Mercury outboard with the cowling removed and propeller off in the service shop.

Last reviewed: 2026-10-21

Mercury Premier Dealer·Gores Landing, ON·Quote builder available

Quick answer: Spring commissioning brings your Mercury back to operational condition after winter storage. The core work: fuel system inspection, cooling system and impeller check, battery load test, fresh gear lube verification, spark plug inspection, propeller check, and a first run with the cooling-water supply approved for your exact engine. Request service at hbwservice.ca in February or March if you want the boat ready for the May long weekend.

Need your PCOC? Take the online course through HBW's MyBoatCard referral link and use HARRIS15 for 15% off.

::cta variant: inline heading: Print the Spring Launch & First-Run Checklist body: Use this one-page dockside aid before launch, at first start and during the first water test. The operation and maintenance manual matched to your engine serial number still controls. primaryLabel: Download spring checklist (PDF) primaryHref: /downloads/mercury-spring-launch-first-run-checklist-hbw.pdf ::

Why This Matters More Than You Think

The motor sat for five or six months. Fuel settled. The battery discharged. Rubber components stiffened. Impellers flattened under compression. Putting the boat in the water without running through this list is a reasonable way to spend a long weekend at the dock instead of on the water.

The customers who call us in late May asking why the boat won't start almost always skipped spring commissioning. The ones who book in February or March are usually on the water by the long weekend in May.

Spring commissioning is not the same job every time. Five things affect how aggressive it needs to be:

Quality of last fall's winterization. A properly winterized motor needs verification. A skipped or rushed winterization is a different conversation.

Storage conditions. Indoors under cover is gentlest on a motor. Outdoors uncovered all winter is harder on fuel systems, electrical, and rubber components.

Motor age. Older motors, pre-2010 FourStrokes, 2-stroke carbureted engines, often need more attention on the fuel system and ignition.

Hours of use last season. A motor that ran 200 hours last summer is in different condition than one that ran 30.

Your plans for the new season. If you're starting the season with a long offshore trip or a tournament weekend, err on the thorough side.

The Spring Commissioning Checklist

Work through this in order. The sequence matters, you don't want to start the motor before you've confirmed cooling water is flowing.

Step 1, Visual Inspection (Start Here, Before Touching Anything)

Walk the boat before you do anything else:

Hull. Cracks, soft spots, mouse intrusion in storage areas or cabin. Evidence of rodents is common on boats stored outdoors.
Motor cowl. Cracks, missing fasteners, mouse damage to wiring or hoses under the cowl.
Transom area. Soft spots, cracks, mounting bolt tightness.
Trailer. Tires for age and pressure, bearings, lights, safety chains, ball coupler, breakaway cable if equipped.

A mouse that wintered in your boat can do more damage than a winter freeze. Check carefully.

Step 2, Battery and Electrical

Reconnect the battery if it was disconnected for storage.
Load test the battery. Charge and test it using the battery manufacturer's procedure, and confirm it meets your exact engine's chemistry and cranking requirements.
Clean and tighten terminals. Corrosion at the terminal is an invisible source of hard-starting and charging problems.
Test electrical systems with key on, engine off: bilge pump, lights, gauges, electronics, fish finder, VHF.

At 4–5 years old, give the battery particular attention during testing. Replace it if its condition or test result fails the battery or engine requirements.

Step 3, Fuel System

Check the fuel tank for water or contamination. Water in the tank is more common after outside storage and in humid conditions.
Inspect fuel lines for cracks, brittleness, or stiffness. Ethanol-blended fuel is hard on rubber over time.
Replace the fuel filter if you're at or past service interval (typically annual or 100 hours).
Add fresh fuel. Check stored fuel for deterioration, water or phase separation before using it. Do not run contaminated fuel through the engine; have it safely removed and disposed of. Follow the exact manual for stored fuel and stabilizer use.
Use ethanol-free fuel. We sell ethanol-free marine gas on-site at HBW. It's easier on carburetors, fuel lines, and small-engine fuel systems than the 10% ethanol at the pump.

Step 4, Cooling System

Check the water-pump schedule and cooling symptoms. Many Mercury manuals place water-pump service at an expanded interval around 300 hours or three years, while other models or conditions differ. A weak telltale, reduced water pressure, or overheat warning needs diagnosis now.
Check cooling indication. Locate the indicator outlet shown in your exact manual. Check it immediately after starting and follow the model's stop-and-inspect instructions if flow is absent or abnormal. Stop the engine before inspecting the intakes. A steady telltale alone does not prove the whole cooling system is healthy.
Inspect anodes. Replace them according to the exact manual, commonly when about half consumed, and use the correct material for the water.

First start of the season

Spring commissioning in the order that matters

Skip the order and you'll diagnose a problem you created. Run these in sequence the first day out of storage.

Fuel system check

Is the fuel from last fall still in the tank, and was it stabilized?

Check how the fuel was stored and inspect the system for leaks. Stabilizer does not turn stale fuel fresh again. If the fuel's condition is doubtful, have it assessed and removed safely if needed; service the filters on the motor's schedule.

Water pump and impeller

Is water-pump service current under your exact manual, and are there any cooling symptoms?

Check the service history against the model's hours and calendar interval. Unknown history, reduced water pressure or overheating needs inspection; a telltale stream alone does not prove the pump is healthy.

Battery and electrical

Does the battery hold a load test, and are all connections clean?

A normal resting voltage does not prove the battery can crank the motor. Test it using the battery manufacturer's criteria. Inspect cables and terminals; clean, tighten, and protect connections using the approved isolation and maintenance procedure.

First start with approved cooling water

Is the cooling-water supply and first-start setup approved for this exact motor?

Follow the manual's starting, idle and cooling checks. Stop for abnormal flow or warnings, then inspect as directed. A flushing connection does not automatically permit running the engine.

First water trial

Once commissioning checks pass, does the motor reach its specified wide-open-throttle (WOT) range on the water with the normal load?

Confirm the exact model's range and any break-in restrictions first. Test only in safe conditions. An out-of-range reading calls for a check of load, propeller, hull condition, and engine performance before more full-throttle use; it does not identify one cause by itself.

🔧

Want us to handle it?

Spring commissioning at HBW is free for HBW winter storage customers, $99 otherwise. Includes all five steps above plus a lake test when possible. Book at hbwservice.ca.

Step 5, Lubrication

Check engine oil level (FourStroke). Use the exact manual's check procedure and keep the level within its specified operating range; do not overfill. If it looks milky, water got in, that's a shop visit before you run it.
Check gearcase lube. Should have been changed at winterization. If it looks milky or you're not sure it was done, change it now. A milky gearcase means a seal is leaking, again, shop before running.
Lubricate steering and shift cables. Stiff cables cause slow, hard shifts that wear the gear selector.
Grease swivel pivots and zerk fittings. Tilt tube and swivel pin on the motor, and any grease points on the rigging.

Step 6, Spark Plugs and Ignition

Inspect spark plugs. Replace at the interval in your owner's manual, which varies by model. Fouled plugs are a common cause of hard-starting and misfires after storage.
Check plug wires for cracks or damage on older motors with plug wires (not applicable to modern direct-ignition motors).
Check starting behaviour using the exact manual's approved cooling-water supply and starting procedure, see Step 8.

Step 7, Propeller and Lower Unit

Inspect the prop. Nicks, bends, and edge damage reduce efficiency and can cause vibration that damages the gearcase. Minor nicks can be dressed with a file. Bent blades need a prop shop.
Check for line wrap. Monofilament around the prop shaft is one of the most common seal-killers. Cut it off carefully.
Check shifting on the water at idle. Do not force the control into gear with the engine stopped. After launch, verify forward, neutral and reverse using the model's shifting procedure; binding or grinding needs diagnosis.

Step 8, First Run With the Correct Cooling-Water Supply

Complete the pre-start checks before launch. The first-run setup depends on your exact motor:

Confirm the water supply first. Use the engine position, attachment and procedure approved in your exact manual, or run with the engine properly submerged. Some flush ports are for engine-off flushing. Follow the specified propeller precautions before any out-of-water run.
Start the motor using its prescribed starting procedure and cranking limits. Slow cranking and normal cranking without starting need different diagnostic checks.
Check cooling indication immediately as the model's manual directs. Stop for absent or abnormal flow or an alarm. Stop the engine before inspecting the intakes; do not keep restarting to see if the warning clears.
Observe the first run for leaks, unusual noise and warnings, staying within the exact manual's run-time and RPM limits.
Check trim and tilt in a safe setup, within the engine-position limits for the running or stopped motor. Maintain the approved cooling-water supply.
Keep an out-of-water run at the manual's permitted idle speed. Save throttle-response and propeller-load checks for a safe water trial after commissioning checks pass.

If anything sounds wrong, smells wrong, or shows a warning light, stop. That's a shop visit, not a "let's see what happens on the water" situation.

Step 9, Trailer and Accessories

Trailer bearings. Check the service history against the trailer and hub manufacturer's instructions; grease-packed, oil-bath and other bearing systems have different service procedures.
Trailer tires. Check pressure, look for sidewall cracks. Tires older than 5–6 years should be replaced regardless of tread, the rubber hardens.
Lights. All of them. Brake lights, turn signals, running lights.
Safety chains and breakaway brake (if equipped).

Step 10, Documentation

Update your service log with date, hours, and what was done.
Verify Pleasure Craft Licence (PCL) is current. Expired PCL is a fine on the water.
Confirm insurance is renewed for the season.
Check that Pleasure Craft Operator Card (PCOC) is accessible in the boat.

What HBW Does at Spring Service

If you'd rather have us handle commissioning:

We cover the full checklist above plus computer diagnostics on Mercury SmartCraft systems, lake-test after the bench work, and a written record of everything done. For engine repairs, we only service Mercury and MerCruiser.

Schedule at hbwservice.ca. Book before April if May launch timing matters. After the May long weekend, spring service demand usually gets heavier, so earlier requests are easier to plan around.

What we see at HBW

The spring no-starts that fill our May schedule almost all trace back to the same three things: untreated fuel that sat all winter, batteries that quietly died in storage, and impellers past their interval. None of them are expensive to catch in March. All of them are expensive to discover on launch day. If the boat sat outside uncovered, add mouse damage to the list. We find chewed harnesses every spring.

Related guide: Mercury spring run-up checklist for Ontario.

Ready to Book Spring Service?

Want the boat ready for the long weekend? Book spring service at hbwservice.ca.

Harris Boat Works | Since 1947 | Mercury Marine Premier Dealer | Gores Landing, ON

Frequently Asked Questions

How long should I flush the motor before the first start of the season?: Follow the exact engine manual for cooling-water supply, engine position, propeller precautions and permitted run time. Some flushing ports are engine-off only, while other approved procedures require idling. Never assume a hose fitting permits running. At first start, check the specified cooling indication immediately and stop for absent or abnormal flow or warnings.
My motor was properly winterized, can I skip spring commissioning?: No. Proper winterization protects the motor over winter, but commissioning is about checking what happened while it sat. Fuel lines age. Rodents occasionally nest in engine compartments. Electrical connections corrode. Battery voltage drops. Even a well-winterized motor benefits from a visual inspection and a first start using the exact manual's approved cooling-water setup.
When should I change the gear oil on my outboard?: Change gear oil every season or every 100 hours, whichever comes first. Spring commissioning is an ideal time if it wasn't changed at fall winterization. The critical check is for milky oil: milky gear oil means water has entered the lower unit through a damaged seal. If you see milky oil, do not run the motor, get it to a service shop immediately. Harris Boat Works services Mercury and MerCruiser engines.
How do I know if water got in the lower unit of my outboard?: The primary indicator is milky or coffee-coloured gear oil when you remove the drain plug. Normal gear oil is dark amber or reddish. Other signs include grinding noises from the lower unit while in gear, resistance when shifting, or visible rust around the drain plug. If you find milky oil, don't run the motor, bring it in for inspection. Caught early, it's a seal replacement; run it with water in the gear case and you're looking at a full lower-unit rebuild.
How much does professional spring commissioning cost in Ontario?: Ontario shops typically charge $150-$350 CAD. At HBW the spring check is free for our winter storage customers and $99 for everyone else. A basic commissioning is at the lower end; a commissioning that includes gear oil change, spark plug inspection, impeller check, and fuel filter replacement costs more. Harris Boat Works provides an upfront scope before starting, request service at hbwservice.ca.
What's the best time to book spring commissioning near Rice Lake or the Kawarthas?: Book in February or March. By mid-April, most service departments near Rice Lake are fully booked through May. If you're targeting Victoria Day weekend as your first launch, your motor needs to be in the shop at least 3-4 weeks beforehand. Harris Boat Works has been doing spring prep on Rice Lake since 1947, early booking means your boat is done and waiting when the lake opens.
Should I replace the water pump impeller every spring?: You do not need to replace the impeller every spring. Follow the exact manual for the engine; many Mercury schedules place water-pump service at an expanded interval around 300 hours or three years, while model and operating conditions can change it. A weak telltale, reduced water pressure, or overheat warning needs diagnosis sooner.
Can I do spring commissioning myself, or do I need a dealer?: Most of the commissioning checklist is DIY-friendly: battery check, fuel line inspection, propeller inspection and a first start using the exact manual's approved setup, with control checks on the water at idle. Where you need a dealer: EFI diagnostic checks, impeller replacement, fuel injector service, and hydraulic steering work. If you find milky gear oil, unusual start behaviour, or warning alarms, stop and call a dealer. For engine repairs, Harris Boat Works only services Mercury and MerCruiser, call 905-342-2153.
Does ethanol in fuel cause problems during spring start-up?: Yes. Ethanol-blended fuel (E10) can cause issues if it wasn't treated before storage. Ethanol absorbs moisture, and fuel sitting over winter can phase-separate into an ethanol/water layer that won't combust properly and can damage fuel system components. Prevention: use fuel stabilizer at storage, and ideally drain the fuel system before long storage. In spring, if you're starting with old untreated fuel, drain and replace it. Most Mercury EFI four-strokes are rated for E10, do not use E15 or higher.

Harris Boat Works · 5369 Harris Boat Works Rd, Gores Landing, ON · (905) 342-2153

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