Yacht Service

Yacht and Boat Oil Change & Marine Engine Service - Seattle, WA

Experienced marine technicians on Lake Union — diesel and gas, recreational and light commercial. By appointment, right at our dock.

Reviews from boaters

Google Reviews

4.9

Based on Google ratings

Scott M.

Seattle, WA

Jul 5, 2025

Such a convenient resource on Lake Union. Ample room on the dock to pull up, fuel up, pump out, grab some snacks or beverages in their well-stocked shop. Always clean, always friendly.

Julia J.

Tacoma, WA

Apr 30, 2025

Always great service. One-stop shop and fuel. Also have had oil changes and engine servicing done here.

Robert B.

Seattle, WA

Aug 4, 2022

Morrison's is THE place to go for all your boating and yachting needs. Convenient and friendly.

See all reviews on Google →

Service Menu

From a quick oil and filter change to seasonal tune-ups, we keep your vessel running reliably all year.

Oil & Filter Service

Full crankcase drain and refill with manufacturer-spec marine oil. We install a new OEM or equivalent primary filter, torque to spec, check the dipstick level hot and cold, and wipe down the bilge.

Fuel Polishing & Old Fuel Removal

Diesel grows algae and water in the Pacific Northwest. We pump out contaminated fuel, filter it through a Racor-style separator, clean the tank bottom, and install new primary and secondary fuel filters.

Batteries

Load-test your starting and house banks. We stock Group 24, 27, 31 and 4D AGM / deep-cycle batteries, clean terminals, and replace corroded cables and wing nuts.

Generator Service

Oil and filter changes, impeller swaps, belt and hose inspection, and load-testing for Westerbeke, Northern Lights, Onan, Kohler and Fischer Panda marine generators.

Transmissions & Impellers

Change transmission fluid in ZF, Twin Disc, Velvet Drive and Borg-Warner units. Replace raw-water impellers before they fail — we stock common sizes right at the dock.

Full-System Tune-Ups

Belts, hoses, zincs, coolant, fuel filters, air filters, belt tension and a full visual inspection — a clean once-over before the cruising season or a long Inside Passage run.

Oil & Filter Reference

We stock the oils and filters your engine actually calls for — no guessing, no wrong weight.

Marine Diesel Oils

15W-40 CI-4 / CJ-4

Year-round Pacific Northwest — Cummins, Cat, Detroit, John Deere

10W-40 Synthetic

Cold-start protection and high-output engines — MAN, Volvo D-series

SAE 40 Straight

Warm-season only and older mechanical engines — Cat 3208, Detroit 2-strokes

15W-40 Synthetic Blend

Yanmar, Westerbeke, Northern Lights generators and auxiliaries

Marine Gas / Sterndrive Oils

25W-40 Mineral

Standard MerCruiser and Volvo sterndrive/inboard recommendation

20W-40 Synthetic Blend

High-hour, warm-climate or tow-sport use — MerCruiser, PCM

15W-40

Older Crusader / PCM inboards and outboard pre-mix tanks

10W-30 / 10W-40

Marine Engines We Service

Our techs work on the diesel and gas platforms most common to Lake Union and Puget Sound boats.

Marine Diesel Engines

Cummins Marine Diesel

QSB 5.9 / 6.7, QSC 8.3, QSM 11, 6BT, ISB, ISL

The most common recreational diesel on Lake Union. We stock Fleetguard and Cummins-spec filters, carry 15W-40 and straight 40-weight CI-4/CH-4 oil, and handle valve adjustments, aftercooler cleaning, and raw-water pump rebuilds.

Yanmar

4JH, 6LP, 6LY, 8LV, 3YM, 4LV

Popular in sailboats and smaller trawlers. We use Yanmar-spec 15W-40 or 10W-30 depending on block generation, replace OEM canister filters, and inspect the heat-exchanger and mixing elbow for corrosion every service.

Volvo Penta Diesel

D3, D4, D6, D9, D11, D13, IPS 400 / 500 / 600

Common in express cruisers and IPS pod-drive yachts. We use VDS-4.5 15W-40 synthetic blend, reset service reminders, and check the pod-drive gear oil and seals while the boat is in the water.

Caterpillar (Cat)

3208, 3116, 3126, C7, C9, C12, C18, C32

Heavy-duty yacht and commercial engines. We stock Cat-specific filters, use Cat DEO 15W-40 or SAE 40, and inspect aftercoolers, turbos and fuel-transfer pumps during each oil change.

MAN

i6 730 / 800 / 1000, V8 1200 / 1550, V12 1900

High-output German yacht diesels found on large motoryachts. We use MAN-approved 10W-40 synthetic, pull MANN-HUMMEL or Hengst filters, and check the common-rail injectors and SCR / DEF system if equipped.

Detroit Diesel

6V92, 8V71, 8V92, Series 60, DD13 / DD15

Classic two-strokes and modern four-strokes. We use Detroit Diesel Power Guard 15W-40, inspect the blower and air boxes on two-strokes, and handle EGR / DPF service on newer Series 60 units.

John Deere Marine

4045, 6068, 6090, 6135

Reliable workboat and trawler engines. We stock Deere-spec filters, use John Deere Plus-50 II 15W-40, and inspect the keel-cooler or heat-exchanger zincs at every visit.

Mercedes MTU

Series 2000 (M72, M84, M94), Series 4000 (M63, M73, M93), 8V / 10V / 12V / 16V configurations

High-performance German yacht and commercial diesels found on larger motoryachts and fast patrol vessels. We use MTU-approved 15W-40 or 10W-40 synthetic oil, replace OEM filter elements, and inspect the common-rail fuel system, turbos and charge-air coolers per MTU service intervals.

Westerbeke / Northern Lights

Generators 5–65 kW

Marine generator and auxiliary diesels. We change oil and filters, replace impellers, inspect belts and exhaust elbows, and load-test the output so your generator is ready for the season.

Marine Gas & Sterndrive Engines

MerCruiser

3.0L, 4.3L, 5.0L, 5.7L, 6.2L, 8.2L, 496 MAG, Bravo / Alpha drives

The dominant gas sterndrive and inboard platform. We use Mercury/Quicksilver 25W-40 or 20W-40 synthetic blend, replace the remote oil filter, drain Bravo / Alpha drives, and inspect the sea-water pump impeller and drive bellows.

Volvo Penta Gas

4.3 GXi, 5.0 GXi, 5.7 GXi, 8.1 Gi, V8-380, V8-430

Found in cruisers and sport boats. We use Volvo VDS-3 15W-40 or 10W-40 synthetic, replace the spin-on oil filter and fuel filter, and check the SX / DP-S drive oil and bellows.

Crusader / PCM / Indmar

5.0L, 5.7L, 6.0L, 8.1L, 454, 502, ZR / Raptor / GM marinizations

Common in older inboard cruisers and tow boats. We use 15W-40 or 20W-50 marine oil depending on hours and climate, replace the FL-1 or PF35-style filter, and inspect the raw-water pump and transmission cooler.

Don’t see your engine listed? Give us a call at 206-284-6600 chances are we can help or point you in the right direction.

Book an Appointment

Tell us about your boat and what you need. We’ll reply to confirm a time. Prefer to talk? Call 206-284-6600 or email morrisonsnorthstar@gmail.com.

How It Works

1

Call to schedule

Tell us your engine make, model and hours. We'll pull the right oil, filters and parts.
2

Tie up at our dock

Bring the boat in during your appointment window — no need to haul out for routine service.
3

We do the work

Oil change, fuel polishing, or whatever service you booked — performed by experienced marine techs.
4

Back on the water

Top off the tank, grab a coffee from the store, and you're good to go.

Summer Hours