Repair
Valve adjustment and tune ups for marine diesels
Valve clearances drift as an engine accumulates hours, and once they are out the engine loses compression, starts poorly and burns more fuel. Adjustment is routine maintenance that gets skipped for years on most boats. It is one of the cheapest ways to get performance back on a high hour diesel.
Clearances drift and nobody resets them
Manufacturers publish a valve adjustment interval and it is one of the first things dropped from a maintenance schedule, because the engine keeps running without it. What actually happens is a slow loss of compression and economy, and eventually valve seat and face damage that costs far more than the adjustment would have.
What is included
- Valve clearance measurement against specification
- Adjustment to manufacturer tolerance
- Valve train and rocker gear inspection
- Valve cover gasket replacement
- Compression check before and after where warranted
- General tune up items and belt tensioning
How it works
Measure
Every clearance gets measured cold and recorded against specification before anything is touched.
Adjust
Set to tolerance, with the valve train inspected for wear while the covers are off.
Confirm
Starting, running and where relevant compression get rechecked to confirm the gain.
Marine diesel valve clearances drift with accumulated running hours, and clearances left out of specification reduce compression and fuel economy and can eventually damage valve seats and faces.
Related repair work
Diesel Repair
Engine, transmission and generator service on marine diesels, from routine maintenance through a complete repower.
Engine Diagnostics
Find the actual cause before parts get bought, using engine management data, live readings and a borescope.
Engine Repower
Replacing tired engines with new power, including the mounts, controls, exhaust and propeller match that make it work.
Valve Adjustment: common questions
How often do marine diesel valves need adjusting?
Follow the interval in your engine manual, which is commonly expressed in running hours. On engines with no service history it is worth checking regardless of what the hour meter says.
Will valve adjustment fix hard starting?
Frequently, yes. Clearances out of specification reduce compression, and low compression is a common cause of hard starting on an otherwise healthy diesel.
Is this included in a survey?
Valve clearance is not adjusted during a survey, but compression is measured, and a compression result that suggests clearance problems will be reported.
Tell me what the engine is doing
Describe the symptom on the phone and most of the time the problem is narrowed before I arrive. Surveys are booked around your sea trial date.