The Marine Knowledge Network
Field write-ups from real jobs - what broke, what fixed it, torque specs and part numbers included. Ask it a question; specs answer inline.
Sea Trial Checklist for Mechanics
Why a structured sea trial A sea trial is where your repair either proves itself or fails privately, with you aboard instead of the customer's family. It's also a billabl...
Quoting a Repower: The Mobile Mechanic's Guide
The opportunity and the trap A repower is the biggest ticket a mobile mechanic writes — and the easiest place to lose money or reputation. The engine price is the visible...
Reading Marine Spark Plugs: A Diagnosis in Your Hand
Why plugs are worth reading every time Spark plugs are free diagnostic data. Any time plugs come out — tune-up, compression test, winterization — lay them out in cylinder...
The On-Water Diagnosis Kit: What's Actually in the Bag
The premise A mobile marine mechanic's first visit is diagnostic. You can't carry the shop, but you can carry enough to diagnose 90% of calls in one trip — which is what ...
Bilge Pump Setup Done Right
The system that saves boats while nobody watches A bilge pump setup is only as good as its weakest crimp. When you're aboard for any job, a two-minute bilge audit is chea...
Shrink Wrap vs Indoor Storage: The Honest Trade-offs
The question every fall Customers ask which storage option is "worth it." Give them a straight comparison — and remember the winterization underneath matters more than th...
Transom Rot Assessment: Do This Before You Hang an Engine
Why this is a mobile mechanic's problem Every repower quote, every big outboard swap, every "the transom flexes when we trim" call starts here. Hanging a new engine on a ...
Hydraulic vs Cable Steering: Diagnosis and Service
Identify the system first - Mechanical cable rotary or rack : a helm turns a push-pull cable into the outboard's tilt tube. Cheap, simple, and prone to seizure. - Hydraul...
Anodes and Galvanic Corrosion, Explained for the Dock
The problem in one paragraph Put two different metals in water that conducts salt especially and you've built a battery: the less noble metal dissolves to protect the mor...
Gelcoat Crack Repair: From Spider Cracks to Gouges
First, diagnose the crack Gelcoat is a cosmetic skin over structural laminate. The repair only lasts if you know why it cracked: - Spider/crazing webs radiating from a po...
Trailer Surge Brakes: Inspection and Service
How surge brakes work 30-second version A sliding hydraulic actuator in the trailer tongue compresses when the tow vehicle slows; that motion pushes a master cylinder tha...
Marine Batteries and Wiring Basics
Battery types in the field - Starting: thin plates, high cranking amps, hates deep discharge. - Deep cycle: thick plates for trolling motors, house loads. - Dual purpose:...
Boat Trailer Bearing Service (and Bearing Buddy Myths)
Why boat trailers eat bearings Boat trailer hubs get dunked hot into cold water at every ramp. The temperature drop contracts the air inside and pulls water past the seal...
Boat Trailer Lights and Wiring Troubleshooting
The pattern behind most trailer light calls Trailer light faults are 80% grounds and connectors, 15% corroded bulb sockets, 5% actual broken wires. Boat trailers are the ...
Submerged PWC / Water Ingestion: The First 48 Hours Matter
Time is the enemy A submerged or hydrolocked PWC engine starts corroding internally the moment it comes out of the water. Handled within a day or two, many survive; left ...
Pontoon Boat Inspection: Logs, Leaks, and Pre-Season Checks
Pontoons hide their problems below the deck A pontoon that "sits low on one side" or "feels sluggish" usually has water inside a log toon . Aluminum logs are chambered; a...
Sea-Doo Winterization Step by Step
Why PWC winterization is its own animal A Sea-Doo's exhaust system and intercooler on supercharged models trap water that outboards would drain by gravity. Freeze damage ...
Yamaha WaveRunner No-Start Diagnosis
Sort the complaint first "Won't start" means three different jobs: no crank , cranks but no fire , or fires and dies . Get the customer to describe it or video it before ...
Sterndrive Gimbal Bearing and U-Joint Noise Diagnosis
The sounds and what they mean Drivetrain noises through a sterndrive transom are diagnosable by ear before any disassembly: - Chirp/squeal at idle in gear, changes or wor...
Sea-Doo Jet Pump Wear Ring Inspection and Replacement
What the wear ring does Sea-Doo pumps run a plastic wear ring around the impeller instead of a machined metal housing. The design saves the impeller when debris passes th...
MerCruiser Raw Water Impeller: Alpha vs Bravo Differences
Know which drive you're standing behind The single most common MerCruiser quoting mistake is assuming all sterndrive impeller jobs are the same. They are not: - Alpha One...
Exhaust Manifold and Riser Inspection on Marine V8s
The quiet engine killer On raw-water-cooled MerCruiser, Volvo Penta, and inboard V8s, exhaust manifolds and risers elbows are water-jacketed castings that rust from both ...
Volvo Penta Sterndrive Annual Service Essentials
Scope Applies to common Volvo Penta SX and DPS-style drives. Duoprop systems add a second prop and seal set but the logic is the same. Always confirm intervals and proced...
Sterndrive Spring Recommissioning Checklist
Before it touches water Sterndrives hide winter damage better than outboards — a cracked block or split bellows may not announce itself until the boat is floating. Work t...
MerCruiser Alpha One Bellows Inspection: The Boat-Sinker Check
Why this is the most important sterndrive inspection The u-joint bellows is the rubber boot sealing the hole in the transom where the driveshaft passes. When it cracks, t...
MerCruiser Winterization (Raw-Water-Cooled)
The stakes A raw-water-cooled MerCruiser holds water in the block, manifolds, and drive after every run. One hard freeze with water in the block cracks it — the most expe...
Prop Hub Replacement and the Spun-Hub Field Call
What a spun hub is Most props isolate the blades from the prop shaft with a rubber or composite hub designed to slip on impact instead of breaking the gearcase. After a s...
Ethanol Fuel Problems in Boats: What It Does and How to Treat It
Why boats suffer more than cars Cars burn a tank in a week; boats store fuel for months in vented tanks in humid air. E10's ethanol is hygroscopic — it pulls water out of...
Two-Stroke vs Four-Stroke Oil: What Goes Where and Why It Matters
Two different jobs Two-stroke oil is consumed — mixed with fuel premix or injected, it lubricates rings, bearings, and crank as it passes through and burns. Four-stroke o...
Prop Selection Basics: Pitch, Diameter, and Hitting the RPM Window
The one rule At wide-open throttle with a normal load, the engine must turn within the WOT rpm range published in the service manual. Everything about prop selection serv...