Replacing an older 2-stroke 70–90 HP outboard with a new Mercury 90 HP FourStroke EFI on a 17-foot aluminum runabout typically runs $13,000–$16,000 all-in at Harris Boat Works in Gores Landing. That covers the new motor, removal of the old 2-stroke, new controls and cables, propeller selection, fuel system inspection, and a full water test on Rice Lake. Timeline is 2–4 weeks. This is the reliability-and-warranty repower, owners trading a tired carbureted 2-stroke for a quiet, clean, factory-warrantied modern FourStroke.
Last reviewed: 2026-05-24
Quick answer: Replacing an older 2-stroke 70–90 HP outboard with a new Mercury 90 HP FourStroke EFI on a 17-foot aluminum runabout typically runs $13,000–$16,000 all-in at Harris Boat Works in Gores Landing. That covers the new motor, removal of the old 2-stroke, new controls and cables, propeller selection, fuel system inspection, and a full water test on Rice Lake. Timeline is 2–4 weeks. Build a quote at mercuryrepower.ca.
Replacing an older 2-stroke 70–90 HP outboard with a new Mercury 90 HP FourStroke EFI on a 17-foot aluminum runabout typically runs $13,000–$16,000 all-in at Harris Boat Works in Gores Landing. That covers the new motor, removal of the old 2-stroke, new controls and cables, propeller selection, fuel system inspection, and a full water test on Rice Lake. Timeline is 2–4 weeks. This is the reliability-and-warranty repower, owners trading a tired carbureted 2-stroke for a quiet, clean, factory-warrantied modern FourStroke.
Key facts
- Old motor: 70–90 HP 2-stroke (Mercury Sport or discontinued Evinrude legacy)
- New motor: Mercury 90 HP FourStroke EFI
- Boat: 17-foot aluminum runabout
- Cost range: $13,000–$16,000 CAD all-in
- Timeline: 2–4 weeks
- Warranty: Mercury Limited Warranty, confirmed at quote
- Noise reduction: roughly half at idle vs old 2-stroke
- Fuel improvement: roughly 30% better at cruise
What was on the boat before?
The starting motor is a 1990s-or-early-2000s carbureted 2-stroke in the 70–90 HP range. Sometimes it's an older Mercury Sport. Often it's a discontinued legacy 2-stroke from Evinrude, a brand that stopped making outboards in 2020 and is no longer supported by its original parts pipeline. Either way, the motor is the same story: it ran for a long time, it's finally tired, and parts for a proper rebuild are harder to find than they used to be.
The boat is usually a 17-foot aluminum runabout owned by someone who has had it for 15 to 25 years. They love the boat. They aren't interested in trading it. They just want a motor that doesn't need a 2-stroke oil top-up at every fill, doesn't blow smoke on cold starts, and doesn't rattle the dock when warming up.
Why upgrade from a 2-stroke to a Mercury 90 FourStroke EFI?
Reliability is the headline. Modern EFI 4-strokes start clean on a cold morning without choke fiddling, idle smooth, and don't foul plugs sitting overnight. They're computer-managed, no carbs to clean, no float bowls to drain, no jets to rebuild.
Noise is the second. A modern Mercury 90 FourStroke runs at roughly half the noise of a comparable old 2-stroke at idle and trolling speed. For early-morning launches and conversation in the boat, this is the change owners notice first.
Fuel is the third. Modern EFI burns roughly 30% less fuel at cruise than a carbureted 2-stroke of the same HP. No oil mixing, no jug of 2-stroke oil every other tank. Over a 5-month Ontario season that adds up.
Warranty closes the deal. A brand-new Mercury carries the current Mercury Limited Warranty plus any active promotional coverage, which we confirm at quote. That factory backing is the kind of peace of mind no 25-year-old 2-stroke can offer.
What did the job involve?
The work is a little more involved than a Mercury-to-Mercury swap. We confirm the transom rating, pull the old 2-stroke, and inspect the transom skin carefully, older 2-strokes sometimes leave water intrusion or stress cracks that need to be addressed before a new motor goes on. If the transom checks out, we install the Mercury 90 FourStroke EFI with new bolts, new controls, new throttle and shift cables, a new tach harness, and a new fuel primer bulb.
Because the old motor used a different control layout, we always replace the helm controls rather than try to make old ones work. That's included in the quote. Propeller selection, usually a 13.25-inch diameter aluminum or stainless in the 17–19-inch pitch range, happens on the water during the test.
Water test on Rice Lake confirms WOT RPM lands in Mercury's spec band, gauges read clean, and steering is right. Pickup-only at Gores Landing, we don't ship or deliver. See our repower process page for the full sequence.
What did it cost?
All-in lands between $13,000 and $16,000 CAD. The Mercury 90 FourStroke EFI sits in the $8,000–$14,000 mid-range FourStroke band, and the new controls, cables, prop, removal of the old 2-stroke, fuel system work, and water test build the rest. Trade-in on an old 2-stroke depends heavily on brand and condition, older Mercury Sport trade-ins still carry some resale value.
Discontinued legacy 2-strokes have less trade value but we still take them case by case.
Financing is 7.99% APR over $10,000 on approved credit. A $500 deposit holds the order. For the full pricing picture, see our Mercury repower cost guide.
Frequently Asked Questions
- Can you repower an old Evinrude with a Mercury?
- Yes. Evinrude is a discontinued legacy 2-stroke brand and we replace them often. The mounting pattern is similar enough on most transoms that the swap is straightforward, though we always confirm the transom condition and may need new bolts and a new throttle harness.
- Why move from a 2-stroke to a 4-stroke?
- Three reasons. Reliability, modern EFI 4-strokes start clean and idle smooth. Noise, about half the noise at idle. Warranty, a new Mercury carries the current Mercury Limited Warranty plus any active promotional coverage, confirmed at quote. Fuel, no oil mixing and roughly 30 percent better burn at cruise.
- Will the controls from my old 2-stroke work with a new Mercury?
- Usually no. The throttle and shift cables and harness are different. We include new Mercury controls and cables in the repower quote so everything is matched and warrantied.
- How long does this kind of repower take?
- 2–4 weeks from quote signing to water test pickup at HBW. The window is wider than a Mercury-to-Mercury swap because we sometimes have transom rework on an older boat. Pickup-only at Gores Landing.
Visit Harris Boat Works
Harris Boat Works · 5369 Harris Boat Works Rd, Gores Landing, ON K0K 2E0 · Phone (905) 342-2153 · Family-owned since 1947 · Mercury Platinum Dealer, selling Mercury since 1965.
We're the repower side of Harris Boat Works, a family marina in Gores Landing serving boaters since 1947. Two-stroke-to-FourStroke jobs are some of the most satisfying work we do, the boat sounds different the moment you leave the dock.
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