Like with LPG, boats on inland waters have requirements on the storage and fuel supply systems, and these are more onerous for petrol-engined boats. Petrol engined boats are often the cheapest form of powered boating with many small family sized 'weekend' craft targeted at the entry level.
However, bank side petrol stations are not as common as they were and boaters often carry large quantities of spare petrol to avoid running out and getting stuck.
Incident records also show that people are tempted to store petrol inboard without using fire resistant self-draining lockers. They refuel without shutting down the accommodation space and have even been known to mix oil and petrol for two stroke outboard motors in open containers such as buckets.
While not a hard and fast rule, these craft are most commonly used during weekends and holidays. You may need to take this into account when attempting to engage with such boat users, both for timing and the 'holiday' attitude.