Surveys
Mechanical marine surveys that cover what a hull survey leaves out
A mechanical marine survey is a documented assessment of the propulsion engines and generator on a boat or yacht. It covers operation and condition rather than hull structure, and it is the step that tells you whether the machinery you are about to buy is sound. I inspect, test under load, sample the fluids and hand you a written report with photographs.
A hull survey is not an engine survey
Most general marine surveys stop at a visual walk past the engine room. The written scope usually says machinery was viewed where accessible, and anything deeper gets referred out to a mechanic. That leaves the single most expensive system on the vessel unexamined at the exact moment you are deciding what to pay for it. I have spent 20 years inside marine diesels, so the referral stops with me.
What is included
- Visual inspection of engines, mounts, hoses, clamps and belts
- Serial and model verification against manufacturer specification
- Compression test on every cylinder with injectors removed
- Electronic control and engine management computer readout
- Wide open throttle test to confirm the engine and propeller are matched
- Sea trial under load with generators running
- Oil, coolant and transmission fluid drawn for laboratory analysis
- Photographed written report with each finding identified
How it works
Dockside inspection
I go through the engine room cold: mounts, hoses, clamps, belts, exhaust arrangement, control cables and the electrical and cooling systems. Serial and model numbers get checked against what the paperwork claims.
Dock trial and compression
Injectors come out and every cylinder gets a compression reading. I record exhaust temperatures, alternator output, starter amp draw, voltage and belt tension, and pull the engine management data.
Sea trial and report
The vessel runs under load while I log RPM, pressures and temperatures and check the gauges for accuracy. Fluid samples go to the lab. You get the written report with photographs of every finding.
A mechanical marine survey from Jon Diesel Marine includes a compression reading on every cylinder, a wide open throttle test, a sea trial under load, and laboratory analysis of engine oil, coolant and transmission fluid, delivered as one photographed written report.
Related surveys work
Pre-Purchase Engine Survey
The engine half of your buyer's due diligence, documented before you sign and priced against the repairs it finds.
Oil and Fluid Analysis
Laboratory analysis of engine oil, coolant and transmission fluid to catch internal wear before it surfaces.
Video Borescope Inspection
A camera inside the cylinders and passages, so the decision to open an engine is made on evidence.
Mechanical Marine Surveys: common questions
What is the difference between a marine survey and an engine survey?
A general marine survey covers hull, structure, electrical, plumbing and safety equipment, and usually reports on machinery only as far as it is visible. An engine survey is a mechanical examination: compression on every cylinder, engine management data, load testing and fluid analysis. Buyers of diesel powered boats commonly commission both.
When should I get a mechanical marine survey?
Before you close on a boat, before an insurance renewal on an older vessel, and any time an engine is expensive or complex enough that a failure would be a five figure event. It is also worth doing on any vessel that shows an obvious lack of maintenance.
Do you remove the injectors to test compression?
Yes. Compression is read on every cylinder with the injectors out. A survey that skips this step is reporting on how an engine sounds, not on what condition it is in.
Will the report help me negotiate?
That is a large part of what it is for. The report documents condition with photographs, which gives you something specific to take back to the seller, and it lets you budget for the repairs and maintenance the engine actually needs.
Do you survey generators as well as main engines?
Yes. The generator is inspected and load tested alongside the propulsion engines, and it is included in the same report.
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.