Last reviewed: 2026-07-02 > Quick answer: In Ontario, most Mercury outboards hit their 100-hour or annual service at winterization, so the honest cost answer comes from real fall work orders. At our Rice Lake shop, last season's median for a full winterize-and-service ran...
Last reviewed: 2026-07-02
Quick answer: In Ontario, most Mercury outboards hit their 100-hour or annual service at winterization, so the honest cost answer comes from real fall work orders. At our Rice Lake shop, last season's median for a full winterize-and-service ran from about $250 all-in on a small tiller to about $440 on a 150 HP FourStroke, parts included, before HST. Book at hbw.wiki/service.
Search "100-hour service cost" and you'll get American answers: year-round boating states, different labour rates, different math.
Here's the Ontario version, from 4,160 winterize-and-service work orders in our system since 2013. On a Kawartha season, most boats don't hit 100 hours in a year; they hit the calendar first. So Mercury's "100 hours OR annually, whichever comes first" rule means your 100-hour service is almost always your fall service, done when the motor gets winterized anyway.
That's not a dodge; it's the efficient way to buy it. One appointment, one drain of the same fluids, one bill.
Who this is for
You own a Mercury FourStroke, you've seen "100-hour service" in the owner's manual or heard it at the dock, and you want a real number before you book anything. If you're deciding between doing it yourself and paying a shop, this covers that too. The interval rules themselves live in our 20-100-300 maintenance guide.
What a 100-Hour / Annual Service Actually Includes
Mercury's 100-hour and annual service list for a FourStroke, in plain terms:
- Engine oil and filter change
- Gearcase (lower unit) oil change, with a look at what drains out (milky oil = seal problem caught early)
- Spark plug inspection or replacement
- Fuel system check: filters, lines, primer bulb, water-separating filter where fitted
- Grease points, linkages, and corrosion check
- Anodes checked, prop pulled and shaft greased
- In fall, add the winterizing steps: fuel stabilizer run through, cylinder fogging, and cooling system drained
The bundling logic is simple: the annual service and winterization share most of the same labour. Doing them together is one bill instead of two.
Real Numbers From Our Counter
These are medians from last season's completed work orders at our shop (2024-25 season, before HST; as of July 2026). Labour is a flat rate by motor class; parts are what the median job actually consumed (oil, filters, gear lube, plugs as needed, fogging oil, stabilizer):
| Motor class (FourStroke) |
Flat-rate labour |
Median parts |
Typical all-in |
| 2.5 to 20 HP |
$147 |
~$101 |
~$250 |
| 25 to 30 HP |
$161 |
~$110* |
~$270 |
| 40 to 60 HP |
$196 |
~$125 |
~$320 |
| 75 to 115 HP |
$238 |
~$159 |
~$400 |
| 150 HP |
$238 |
~$204 |
~$440 |
*The 25 to 30 HP parts figure is estimated from the classes either side of it; the rest are measured medians.
Two honest notes on that table. First, parts vary by what YOUR motor needs: a plug set on a V6 costs more than on a twin, and a motor that skipped last year's service usually needs more. Second, rates get reviewed each season, so treat these as planning numbers and confirm current pricing when you book your service.
What moves the number up: skipped previous services, a water-separating filter that's never been changed, seized prop hardware, and anything the tech finds in the "while it's open" category. Our service-bill guide covers the habits that quietly inflate invoices.
Why "Cheap" 100-Hour Services Usually Aren't
A $150 quote for a "full service" means something got skipped, and it's usually the gearcase oil or the fogging. Those are exactly the two items that catch expensive problems early:
- Gearcase oil that comes out milky means water is getting past a seal. Caught at service time, it's a seal job. Missed for a season, it can be a gearcase.
- Skipped fogging on a stored motor invites corrosion in the cylinders over five months of Ontario winter.
The labour on our invoices is the real work: 1 to 1.7 hours per motor depending on class. Anyone quoting half that time is doing half the list. Ask any shop for the itemized list before you compare prices; ours is the section above.
DIY vs Shop: The Fair Comparison
Plenty of owners handle oil and plugs themselves, and our DIY winterization guide doesn't gatekeep. The fair framing:
- DIY saves the labour ($147 to $238 by class) and costs you tools, disposal runs, and an afternoon.
- The shop buys you the inspection layer: a tech who's seen hundreds of the same motor, the milky-oil catch, the recommendations line on your file, and a record that helps resale ("full dealer service history" is worth real money when you sell).
- The hybrid many of our customers run: DIY the mid-season oil change, shop the annual fall service. The motor gets professional eyes once a year and you still save.
What we'd skip: DIYing the gearcase and fogging steps if you've never done them. Those are the two where a small mistake gets expensive.
What HBW checks before your motor goes back on the water
Every winterize-and-service at our shop ends with the tech writing recommendations on your file: what's wearing, what to watch, what next season will need. That line is why our customers rarely get surprise failures in July; 13 seasons of work orders show the pattern clearly, and it's the same one our 766-impeller dataset shows. Maintenance you do in fall is reliability you get in summer.
When to Book (Ontario Reality)
Our marina is closed December 1 to April 1, and fall slots fill in order. The efficient move: book your winterize-and-service in late summer for an October slot, and your motor goes into winter serviced, protected, and ready to launch without a spring rush. Spring-only services exist (see the spring commissioning cost guide), but fall is when the full annual service belongs.
Frequently Asked Questions
How much does a Mercury 100-hour service cost in Ontario?
At our Rice Lake shop, last season's medians ran about $250 all-in for small tillers up to about $440 for a 150 HP FourStroke (labour + typical parts, before HST), done as a fall winterize-and-service. Your parts total depends on your motor's plug count and condition. Current-season pricing is confirmed when you book at hbw.wiki/service.
Is the 100-hour service the same as winterization?
They overlap heavily, which is why Ontario shops bundle them. The annual service covers oil, gearcase oil, plugs, fuel system, and inspection; winterization adds stabilizer, fogging, and cooling-system draining. Doing both in one fall appointment shares the labour instead of paying it twice.
My motor only ran 40 hours this year. Do I still need the service?
Yes. Mercury's schedule is 100 hours OR one year, whichever comes first, because oil degrades and moisture accumulates with time, not just use. Most Kawartha boats are calendar-limited, not hour-limited; that's exactly why the fall service exists.
What parts get replaced at a typical annual service?
Engine oil and filter, gearcase oil, fuel stabilizer, and fogging oil on every job; spark plugs and fuel filters as condition and interval require. Median parts spend at our counter last season ranged from about $101 (small motors) to about $204 (150 HP class), before HST.
Can I skip a year to save money?
You can, and the data says you'll give it back later. Skipped services show up in our work orders as seized prop hardware, milky gearcase oil caught late, and fuel-system cleanups that cost more than the service would have. The annual service is the cheap insurance tier.
Do you service motors bought somewhere else?
Yes. Our techs service Mercury outboards regardless of where you bought them, and plenty of our regulars started that way. Put in a request at hbw.wiki/service with your motor details and hours, and we'll slot you into the fall schedule.
Ready to Book Your Service?
Tell us the motor and the season you want covered, and we'll handle the rest, recommendations line included.
Service requests: hbw.wiki/service
Questions? Text: 647-952-2153 or call: 905-342-2153
Address: 5369 Harris Boat Works Rd, Gores Landing, ON
Related guides:
Sources
- HBW service records, Rice Lake: 4,160 winterize-and-service work orders, 2013-2026 (medians from the 2024-25 season)
- Mercury Marine FourStroke maintenance schedules (your owner's manual is the source of truth for your model)
