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

You don't flush the motor before the first start, you run the motor on flushing muffs with a garden hose providing water while it runs. Let the motor warm up at idle for 2-3 minutes with water flowing, verifying the telltale stream is discharging water. Never start the motor, even briefly, without either being in the water or on flushing muffs with the hose running, running dry even briefly can damage the water pump impeller.

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 on the muffs before launch.

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 hbw.wiki/service.

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, first start on the muffs, and control checks. 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)

--- ## 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...

Last reviewed: 2026-09-06

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 test run on muffs before the boat goes in the water. Book early, by late April, shops are running behind. Schedule at hbw.wiki/service.

::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

Reinstall battery if you removed it for storage.
Load test the battery. A battery that drops below 10.5V under load is at end of life. Replace it now, not mid-July.
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.

If the battery is more than 4–5 years old, replace it regardless of how it tests. Old batteries fail suddenly and without much warning.

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. Old gas over six months stale should be used up or drained before the season. Topped-off, properly stabilized fuel from last fall is usually fine.
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 telltale stream. This is the small stream of water from the side of the lower unit. Look for it right away; if there is no steady stream within 30 seconds, shut the motor down.
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?

Stale gas is the #1 spring no-start at our shop. If fuel sat untreated over winter, drain it and start fresh. Replace the fuel filter while you're in there.

Water pump and impeller

Has the impeller been replaced or inspected within the last two seasons?

A rubber impeller hardens and cracks in storage. If you can't remember the last change, do it now. A cheap impeller saves an expensive powerhead.

Battery and electrical

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

A battery that read 12.6V on the bench can still fail under starter load. Wire-brush the terminals and apply dielectric grease.

Flush and dry start on muffs

Will the motor start, idle, and reach operating temp on muffs?

Watch for a steady tell-tale stream within 30 seconds of start. Weak or absent flow means stop immediately and re-check the impeller.

First water trial

Does the motor reach its rated WOT RPM with normal load?

Below the rated band means prop, fouling, or a fuel issue. Above the band means under-propped. Either way, fix before a full day out.

🔧

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 hbw.wiki/service.

Step 5, Lubrication

Check engine oil level (FourStroke). Should be at the full mark on the dipstick. 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 interval (typically every 200 hours or 2 years for FourStrokes). 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).
Test ignition by starting on muffs, 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.
Shift through all ranges. Forward, neutral, reverse should be smooth with no hesitation. Hard or grindy shifts often mean a cable issue.

Step 8, Test Run on Muffs

This is the gate before the boat goes in the water:

Connect muffs to the lower unit cooling water intakes. Make sure they're snug and water is flowing through them before you crank.
Start the motor. It should start within 3–5 cranks on a properly winterized motor. Slow or no-start indicates a fuel or ignition issue.
Confirm the telltale stream within 10 seconds. No stream = stop immediately, find the blockage.
Run for 5–10 minutes. Circulate fluids, warm the motor to operating temperature, listen for anything unusual.
Check trim and tilt. Full range, both directions, no hesitation.
Test throttle response through the full range.

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. Repack if not done in the last 2 years. Bearing failure on the highway is the kind of bad day that sticks with you.
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 hbw.wiki/service. 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 hbw.wiki/service.

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?: You don't flush the motor before the first start, you run the motor on flushing muffs with a garden hose providing water while it runs. Let the motor warm up at idle for 2-3 minutes with water flowing, verifying the telltale stream is discharging water. Never start the motor, even briefly, without either being in the water or on flushing muffs with the hose running, running dry even briefly can damage the water pump impeller.
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 on the muffs before launch.
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 hbw.wiki/service.
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, first start on the muffs, and control checks. 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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