“Before you buy: The Subtle Signals Every Marine Surveyor Learns To Hear”
Buying a boat is emotional. Brokers know it, owners know it, and buyers feel it the moment they step aboard. As a marine surveyor, I’m there to slow everything down—to peel back the excitement just long enough to make sure the vessel is being represented fairly, honestly, and without missing pieces. What continues to surprise me isn’t always what’s said during a survey… It’s often what isn’t.
Brokers and owners usually aren’t trying to mislead anyone, but they’re not surveyors either. Their focus is the sale; mine is the vessel’s condition. And over time, I’ve learned that small comments, passing remarks, or oddly quiet moments can reveal more about a boat’s true story than any glossy listing ever will.
EXAMPLE #1: When a Broker Says “That Tank Hasn’t Been Used in a While”
At first glance, a comment like this sounds harmless. A boat has two tanks; the owner prefers to run off one, and the other “just hasn’t been used.” But to a surveyor, that statement is a quiet alarm bell. An unused tank isn’t just unused — it’s a closed environment where moisture, microbial growth, and contamination have time to develop.
Diesel tanks that sit idle often become breeding grounds for microbial growth (commonly called “diesel algae”). This happens when water condenses in the tank's empty space. Over time, that moisture settles, mixes with trace contaminants, and forms a perfect habitat for microbial activity. When that contaminated fuel is eventually drawn into the system, it can clog filters, shut down the engine, and leave a new owner wondering why a seemingly “simple” vessel has suddenly turned into a service bill.
Sometimes an unused tank is intentionally left unused. Maybe the owner knows the pickup tube is partially clogged. Maybe the tank gasket has deteriorated. Maybe a missing O-ring allowed water to intrude through the tank’s inspection plate or fuel fill on the deck. These are things a broker may not mention simply because they don’t know — but a surveyor hears the possibility in the silence.
What That Comment Might Really Mean
The tank hasn’t been serviced or inspected in years
Condensation buildup has likely occurred
Microbial contamination is likely present
An O-ring or gasket may be compromised
The owner may be avoiding known issues
Switching to that tank may cause an engine shutdown
What Buyers Should Ask
How long has it been unused?
Why doesn’t the owner run off it?
Has it ever been cleaned or polished?
When was the last time the pickup tube or inspection port was inspected?
Prevention
Keep tank full during storage
Replace worn O-rings and gaskets
Polish fuel before use
Clean or service tanks regularly
Cycle both tanks periodically
Takeaway
A simple comment about an unused tank is rarely just an observation. It’s information that deserves attention — and it can prevent a brand-new owner from discovering an avoidable fuel issue the hard way.
As I continue surveying vessels, more of these subtle, real-world scenarios surface — and each one carries a lesson that can help prospective buyers make better decisions. To keep these examples organized, easy to find, and continually updated, I’ve dedicated an entire section of my website to them.
You can explore the full, growing list of “watch out for’s” by clicking here: