Marine diesel engine questions and answers
1062 questions boat owners actually ask, answered plainly and grouped by topic. Every answer links to the guide it comes from if you want the full explanation.
Overheating and cooling
Impellers, heat exchangers, exhaust elbows, strainers and the raw water circuit — the system behind most marine engine failures in Australia.
- How often should a heat exchanger be cleaned?
- Can a heat exchanger be cleaned in place?
- What is the pencil anode?
- Can a leaking heat exchanger be repaired?
- How do I know if mine is blocked?
All 87 questions on overheating and cooling
Fuel, tanks and diesel bug
Contaminated fuel, microbial growth, blocked filters and water in the tank — on a boat the tank causes more trouble than the engine.
- Should I fit a finer filter to catch more?
- Why only in rough weather?
- Will a biocide fix it?
- How do I stop it coming back?
- Will biocide alone fix it?
All 31 questions on fuel, tanks and diesel bug
Gearboxes, sterndrives and shafts
ZF and Twin Disc gearboxes, sterndrive bellows, stern glands, shafts and alignment.
- What oil goes in a marine gearbox?
- Why is my gearbox slow to engage?
- What does the reduction ratio mean?
- Can I change the gearbox ratio?
- My gearbox is slow to engage. Is it rebuild time?
All 44 questions on gearboxes, sterndrives and shafts
Rebuilds, repowers and major work
When to rebuild, when to repower, what a reconditioned engine really is, and what saltwater ingress costs.
- Why won't you publish a price range for a marine engine rebuild?
- Is a rebuild cheaper than a repower?
- What is the biggest hidden cost?
- Does the gearbox get rebuilt at the same time?
- How long does a marine engine rebuild take?
All 51 questions on rebuilds, repowers and major work
Servicing, layup and recommissioning
Service intervals by hours and by calendar, winter layup, recommissioning, and why low hours is not good news.
- How often does a marine diesel need servicing?
- Why is a marine service more expensive than a car service?
- Is the impeller included in a standard service?
- Can I service my own marine engine?
- What is the most commonly skipped service item?
All 44 questions on servicing, layup and recommissioning
Buying a boat and engine surveys
Pre-purchase engine inspections, sea trials, and the findings that should change your offer.
- Do I need survey for a charter boat in Australia?
- Who regulates commercial vessels in Australia?
- Can I use a recreational engine in a commercial vessel?
- What engine records does survey want?
- Does a repower need to be approved?
All 13 questions on buying a boat and engine surveys
Finding and choosing a mechanic
Which trade does which job, mobile versus workshop versus haul-out, and what to ask before booking.
- Will a mechanic come to my mooring?
- What is the most useful thing I can do before calling?
- How do I check someone is an authorised dealer?
- What should I do first when the engine stops?
- Can I keep motoring with an overheat alarm?
All 29 questions on finding and choosing a mechanic
Commercial, charter and workboats
Survey obligations, downtime economics, and how commercial operators maintain engines differently.
- How often should charter engines be serviced?
- Why replace parts that still work?
- What is the most common charter engine failure?
- When should major work be scheduled?
- Does oil analysis make sense across a fleet?
All 18 questions on commercial, charter and workboats
Questions by location
Local conditions, seasonality and access, from the Gold Coast to Port Stephens.