About PartnerShip II

I bought this boat from a broker that took it in on trade from the original owner in Stuart, FL. in January 2020. The running gear was well maintained with about 720 hours but the interior finishes and many of the systems were original to 2003 and needed replacement. After 3 years of upgrades (I am a former auto tech and auto repair shop owner and did almost everything myself) fixing anything that didn’t work and improving on the accommodations and finishes, my wife and I took it on the Great Loop, traveling over 4500nm, crossing our wake in February 2025. The boat operated flawlessly. I just finished making a few more  improvements I realized I still wanted to do and am ready to sell her to the next person. I have a complete Captains Log of everything I have done since taking possession.

Meet PartnerShip II

Our boat, PartnerShip II, is a 2003 Mainship 400 Trawler — and she’s everything we hoped for in a Great Loop cruiser. She’s in excellent condition and has clearly been loved and well cared for by previous owners. Powered by a single 385 hp Caterpillar diesel with just over 1,300 hours, she’s both reliable and economical — the kind of engine that hums along all day without breaking a sweat. The 8 kW Kohler generator keeps everything running smoothly when we’re on the hook, and with only 700 hours on it, it’s practically just getting started.

Our Mainship 400: Home on the Water

When we first stepped aboard the Mainship 400, we knew she was built for adventure. This boat isn’t just a cruiser — she’s a trusted companion for the Great Loop or anywhere the ICW might take you. With her single 385hp Caterpillar diesel, she’s happy to lope along efficiently at 8 to 9 knots, sipping fuel like a true trawler, but she’s got the muscle to pick up speed to around 13 knots when the day calls for it.

What we love most are her wide, secure walkaround decks, solid railings, and the feeling of safety you get moving about — whether it’s early morning dew or a breezy afternoon at anchor. The bow thruster makes docking feel easy, even single-handed, and the SeaWise davit system means launching the 10’ Avon RIB with its 15hp Honda outboard is a breeze when it’s time to explore shorelines or grab dinner in a nearby harbor.

The bridge deck quickly became our favorite hangout. It’s ¾ enclosed, which means open-air living without being at the mercy of the weather. There’s a summer kitchen complete with a propane grill, sink, ice maker, and table — perfect for sunset dinners or morning coffee with a view. It’s one of the largest bridge decks you’ll find on any 40-footer, and it feels like an outdoor living room.

Down below, the cherry wood interior makes the cabin feel warm and inviting — the kind of place where you want to curl up with a book after a day on the water. The salon has two comfortable chairs, a dinette for four, and an entertainment setup that includes a flat-screen TV and Bluetooth stereo. The galley is practical but homey, with an apartment-size refrigerator/freezer, 3-burner propane stove and oven, toaster oven, and even a coffee maker — everything we need for long stretches aboard.

The two-stateroom layout gives us flexibility when friends or family visit. The master stateroom up front has a centerline berth with plenty of storage, and the guest stateroom can be arranged as two singles or converted into a queen. The head, complete with a separate stall shower, is accessible from both the master and the companionway — a small but thoughtful touch that makes life easier.

Outside, the covered cockpit and wide side decks make it easy to move around in any weather, and the large swim platform with boarding ladder is great for quick dips or tying up the dinghy. Between the upper and lower helm stations — both fully equipped with Raymarine electronics, autopilot, radar, and engine controls — this boat is equally comfortable for long-distance cruising or lazy weekend exploring.

The Mainship 400 is more than just a boat — she’s a comfortable, capable home on the water. Whether you’re chasing sunsets on the Chesapeake, crossing Lake Michigan, or working your way down the Tenn-Tom, she’s the kind of boat that makes every mile feel effortless.

Specifications: 

Hull

  • Overall length 42’
  • Beam 14’2”
  • Draft   3’-8”
  • Height 18' with mast up, 17' with mast in lowered position
  • Headroom 6’6”
  • Sleeping Capacity 6+ enclosed bridge lounges
  • Displacement 24,000 lbs. dry
  • Fuel capacity 300 gal twin alum’ baffled tanks
  • Water 130 gal in 2 tanks
  • Holding tank 47 gal

 

Engine

  • Make: Caterpillar
  • Model: 3126TA
  • Serial #: 1ZJ03470
  • HP: 385
  • Full Load RPM: 2800
  • Arrangement: #178-7025
  • High Idle: 3144
  • Performance Spec.: OK2010
  • Dual switchable Racor Pre-filters
  • Fuel polishing system with 3rd Racor filter
  • 1375 hours (as of 10/05/2025)

 

Transmission

  • Make: ZP
  • Model: ZF80A
  • Ratio # 1.96: 1
  • Serial # 46569

 

Propeller

  • Bronze 5 blade
  • 5
  • Right Hand Rotation
  • Spare Bronze 4 blade (Tuned to produce the same speed at the same RPM as the 5 blade.)

 

Generator

  • Make: Kohler 8EOZ 8kw
  • Model: 8EOZ
  • Serial # 747825
  • Engine: Yanmar 3TNE74
  • Start Battery: 24F AGM

 

Bow Thruster

  • Make: Side Power
  • Model: SP95T
  • Serial #:
  • Fly-bridge and lower helm controls
  • New quite props (2025)

 

Windlass and Ground Tackle

  • Lewmar V3 Windlass 12 volt w/ 5/16”” chain/rope gypsy and rope drum
    • Foot controls at bow, switch controls at each helm
    • Chain Gypsy
      • 002, 10mm DIN 766, Campbell 3/8" S4, 5/16" G40, Rope size 1/2 - 5/8, 3-strand and 8-plait (5/8 only)
      • 003 10mm ISO, Campbell 3/8" S3, Lewmar 9.5mm G40 Rope Size 5/8 3-strand and 8-plait Spare
    • Ground Tackle
      • Main Anchor
        • Rocna 33
        • 150’ 5/16”” galvanized chain (New 2024)
        • 50 ft 5/8” marine grade braded nylon rope
      • Spare Anchor
        • Kingston Quickset
        • 9’ ft. 5/16” Galvanized chain
        • 115 ft 5/8” marine grade braded nylon rope

 

  • Davit system, Tender and Motor
  • Seawise Davit System
  • 2004 Avon Rover 310 RIB (161 lbs.)
  • 2003 Honda 15 HP Outboard (115 lbs.)
    • Model BF15D35HA
  • Navigation
    • Additional notes on navigation.
      • All instruments have current updates
      • The chart plotters use Navionics updated to current.
      • Included is a 12” Apple iPad that has Navionics AND Aqua Maps
      • AIS can be seen on chart plotter AND iPad/ iPhone when Wi-Fi is connected to the AIS unit.                                          
  • 40' Mainship Audio/Visual Equipment
  • Samsung flat screen TV
  • Bose home theater surround sound system in the salon
  • Bose interior speakers
  • Dual MXD25 stereo/CD player on the flybridge
  • Kenwood and JBL Marine exterior speakers

 

  • 40' Mainship Electrical System
  • Kohler 8EOZD 8 kW generator with approximately 2 total hours
  • Mastervolt Combi Master 2000 watt inverter / 100 amp battery charger (New 2025)
  • Mastervolt Battery remote monitor system (2021)
  • 50 amp shore power cord
  • 30 amp shore power cord
  • 12 vdc USB outlet at the lower helm
  • 2 12 volt USB outlets below salon table
  • 120 volt dual outlet GFCI protected plug below salon table
  • USB charging ports on the flybridge
  • 12 volt cigarette lighter receptacle flybridge (used for handheld spotlight)
  • Perko battery switches
  • 4 X 6 volt Group GC2 Trojan AGM house batteries (new in 2022)
  • 2 X 6 volt Group GC2 Trojan AGM start batteries (new in 2022)
  • LED bulbs interior, exterior, engine room (2023)

 

  • 40' Mainship Mechanical Equipment
  • Tides Marine dripless shaft seal with secondary seal installed (2024)
  • Groco sea strainers
  • Seastar hydraulic steering system with rebuilt steering cylinder (2025)
  • Dual Racor 900MA fuel filters with a vacuum gauge for the main engine (Switchable while underway)
  • Racor R12P fuel filter for the generator
  • Oil-X-Changer oil change system
  • Side-Power bow thruster with (new propellors 2025)
  • Bennett trim tabs
  • Dometic reverse cycle air conditioning/heating system (2 units)
  • Fresh water manifold with whole boat replaceable water filter cartridge
  • Jabsco fresh water system accumulator tank
  • Jabsco Par-Max 3.5 fresh water system pump (with new spare)
  • Attwood 6 gallon water heater plumbed to engine coolant
      • (No shore power or running generator needed for domestic hot water if you ran the engine)
  • Jabsco electric head (with 2 spare parts kits)
  • Seaflow macerator pump (new 2022)
  • Scad holding tank level display
  • Multiple Spare parts
  • New Cutlass bearing (August 2024)

 

40' Mainship Deck Equipment

  • Lewmar anchor windlass with foot controls and a remote control on the flybridge and at the lower helm
  • Mantus 35 LB anchor
  • Mantus anchor bridle/snubber (2023)
  • Fortress FX-23 anchor
  • Stainless steel double anchor roller
  • 150' anchor chain and 150' nylon rode (marked and painted every 10 feet for easy setting)
  • Double stainless steel anchor rollers
  • Stainless steel Sampson Post
  • Stainless steel rails
  • Stainless steel deck hardware
  • Anchor Washdown system (New 2023)
  • Windshield covers (2024)
  • Hinged mast base (repaired 2025)
  • Mast spreader lights (New 2025)
  • Dock-water connection
  • Fiberglass swim platform
  • Swim ladder
  • New anti-fouling paint in May 2025
  • Hull sides polished and waxed May 2025

 

40' Mainship Safety and Fire Protection

  • Sea-Fire 1301 engine room and lazarette fire suppression systems with auto-shutdown.
  • 2 handheld Fire extinguishers in main salon (2023)
  • 1 handheld fire extinguisher in v-birth
  • 2 Carbon monoxide detectors, 1 in each cabin. (2023)
  • 1 carbon monoxide/ propane detector in galley
  • Smoke detector / CO detector in galley.
  • 4 Rule bilge pumps
  • Bilge high water alarm
  • LIFE ring
  • AFI horns (replaced 2024)

 

Galley:  The galley is located along the starboard bulkhead in the main cabin and features a:

  • dual voltage apartment size refrigerator with separate freezer
  • New toaster over.
  • Princess 3-burner propane stove with working oven (No need to run generator for cooking)
  • Large single basin stainless steel sink with new sprayer handle faucet and soap dispenser.
  • Storage cabinets and drawers with multiple included Tupperware containers.
  • 10 cup Mr. Coffee drip coffee maker
  • Complete cups, bowls, dishes and flatware
  • Assorted knives, serving and other kitchen accessories.
  • Full set of cooking pots, pans, trays, etc.
  • Multiple left-over food storage containers.
  • 3 large watertight storage containers for storing food.

 

Lower Helm: The lower helm is starboard forward in the salon with side deck access door and under-sole storage and features:

  • Full set of Faria engine gauges (New 2020)
  • Cable operated throttle/transmission control
  • Raymarine Axiom+ 9” Chart Plotter with remote micro-SD chip holder.
  • Current Navionics navigation charting.
  • Raymarine ACU-400 Course Computer (new 12/2020)
  • P-70RS Color Autopilot Controller (new 12/2020)
  • Raymarine EV-1 Sensor Core Compass (new 12/2020)
  • Raymarine S100 remote control for auto pilot (new 12/2020)
  • Standard Horizon GX-1850 VHF Marine Radio remote Ram 4 mic unit
  • Standard Horizon handheld radio as a backup
  • Joystick bow thruster control
  • Trim tab and windlass controls
  • Seafire engine shutdown override system
  • Danforth compass

 

Master Stateroom: The master stateroom is located forward and offers an island queen size berth, new reading lights, overhead hatch, 2 portlights, storage drawers and cabinets, hanging lockers, customized under-bed storage, teak/holly Plasteak covered sole with direct access to the head with enclosed shower.  Multiple sets of master linens and blankets included.

 

Guest Room: The guest stateroom is located to port and offers side by side single berths, hanging locker, shelf, storage under the berths, hanging bar, port light, teak/holly Plasteak covered sole and overhead hatch. All linens and blankets included.

 

Head:   The head is to starboard with an enclosed shower.

  • Vacuflush Toilet  (2 New seal kits as spare)
  • Scad black water tank monitor.
  • Stainless Steel Sink and Corian Countertop
  • New faucet (2023)
  • Separate Shower\tub Stall with bi-fold Glass Doors
  • New shower faucet and spray head (2022)
  • Opening Overhead Hatch with screen
  • Portlight with Screen
  • Mirror with Teak Trim
  • Chrome towel rings and towel bar (New 2022)
  • Good storage under sink and behind toilet
  • Locking security door with 2 keys

Flybridge: The flybridge offers a ¾ enclosure, helm centered forward with one captain’s chair and molded seats with new cushions to port and starboard, bench seat with storage on each side, fold-up centerline table and non-skid deck, open aft deck with a summer kitchen with propane grill, sink, and ice maker, small table, and hinged mast and features:

  • Raymarine Axiom+ 12” Chart Plotter (New 3/2021) 4.4.70 software upgrade
  • Raymarine P-70RS Color Auto Pilot Control (New 2022)
  • Raymarine Tri Data depth gauge, speed through water and water temp. (New 2024)
  • Raymarine Quantum Q24D Radar with data cable (new 2023)
  • Standard Horizon GX-1850 VHF Marine Radio with GPS, DSC and MMSI (New 2022)
  • em-trak B924 Class B CSTDMA AIS Transponder with Integrated Splitter, Wi-Fi and Bluetooth (iPhone / iPad / Raymarine control)
  • Bow thruster control
  • Trim tab and windlass controls
  • Seafire engine shutdown override system
  • Danforth compass
  • Reliable cable operated throttle/transmission control
  • Full set of engine gauges (New 2021)
  • Sony Megabass Bluetooth Stereo with speakers
  • Radar mast can easily be lowered by removing 2 screws - can be lowered in 2 minutes or less.

Cockpit: The aft deck offers a hardtop, non-skid deck, transom gate to the fiberglass swim platform and tender, molded steps to the flybridge, wide side deck access, lazarette, and generator access, transom storage compartments and a freshwater hot and cold shower.

 

Audio / Video Equipment:

  • 32" flat screen Smart TV in salon
  • Manufacturer installed Bose AM/FM/CD Player with base speaker and 2 wall mounted speakers 
  • Bluetooth stereo on fly-bridge with remote and separate speakers in main salon.

Spares

  • 3 blade propeller with puller and wrench (stored in engine room)
  • 1 30” round fender
  • 8 tubular fenders
  • 2 inflatable super-sized fenders, used for transiting locks. Deflate for storage.
  • Multiple dock lines of various lengths
  • Container with spare fender lines and air pump.
  • Many, many more spares.

Here is a complete list of all of the improvements made over the course of 3 years.

  • New hull paint job and new bottom paint (2020)
  • 1000 hour engine service included fuel injector and valve adjustment. Done at 725 hours. (2020)
    • Intercooler and heat exchangers removed, cleaned, tested and repainted. (2020)
  • New Lewmar V3 windlass (2020)
  • New engine gauges (2020)
  • New headliner in main salon with new LED lighting (2021) Common problem with Mainships.
  • New forward and guest cabin vinyl wall coverings and headliner with upgraded LED puck lights (2021) Common Mainship problem.
  • New blue top / white underside bimini (Custom designed by the owners) (2021)
  • New Raymarine Auto-Pilot (2021)
  • New Raymarine 9” Axiom+ MFD (2021)
  • New Raymarine 12” MFD (2021)
  • New anchor washdown kit (2021)
  • New Promariner Prosafe failsafe 60amp Galvanic Isolator (2021)
  • New flybridge cushions with new foam (2022)
  • New Plasteak vinyl teak like flooring in hall and berths (No carpet) (2022)
  • New single bowl stainless steel sink, faucet and soap dispenser in galley (2022)
  • 6 6-volt Trojan AGM batteries (2 start, 4 house) (Replaced 12/2022)
  • New exterior window covers. (2022)
  • New upper helm cover (2022)
  • New salon bench seat and backrest. (2022)
  • New Standard Horizon GX-1850 VHF Marine Radio with Remote Ram mic. (2022)
  • New Seaflow Macerator (2023)
  • New Raymarine Radar (2023)
  • Sanded and refinished salon floor (2023)
  • New 3 custom made coral cellular window shades (2023)
  • New CO detectors (1 in main salon, 1 in each cabin)
  • Rebuilt Princess Propane Stove with working oven (2023) (No running generator to make dinner)
  • New CO/Propane detector in galley (2023)
  • New 3 speed 12v. electric fans in each cabin (2023)
  • Plumbed the domestic water heater to engine cooling system to make hot water while underway (No generator needed for hot water)
  • Installed davit system on swim platform. (2023)
  • New full boat water filter (2024)
  • New 150’ 5/16” galvanized anchor chain (2024)
  • New fly-bridge ¾ enclosure (2024)
  • New desktop ice maker (2024)
  • 2 new handheld fire extinguishers (2023)
  • New 32’ SMART TV (2024)
  • New remote-control spotlight (2024)
  • Am/FM radio on flybridge with remote (2024)
  • Starlink Gen. 3 Satellite system (2024) 

Improvements made after returning for our Great Loop trip in February 2025

  • Installed 12-volt POE (power over Ethernet) power source for Starlink Gen. 3 Satellite system (New 2025)
    • Does not require inverter to run Starlink now.
  • Sand blasted and Powder coated radar mast with new spotlights (4/2025)
  • New Bottom Paint (2 coats Pettit Trinidad SR Red) (5/2025)
  • Engine, transmission and generator oil and filter change (5/2025)
  • Replaced engine and generator pencil zincs (5/2025)
  • Replaced 2000 watt inverter (6/2025)
  • Replace raw water pump impeller on engine, cleaned raw water strainers 7/2025
  • New bow thruster gear leg and new quiet running props (5/2025)
  • Flushed and cleaned engine and transmission heat ex-changers. 7/2025
  • Cleaned and painted all rusty parts on engine 7/2025
  • Replaced raw water pump impeller on generator. 8/2025
  • Sanded and painted rusted areas on generator housing 8/2025
  • Replace exhaust hose and vacuum break raw water hoses on generator 8/25
  • New propane BBQ grill in summer kitchen. Not done yet but in the works!!