SOUTH PORTLAND — A boater at Sunset Marina pumped about 100 gallons of fuel into his 28-foot recreational boat Saturday evening before he noticed it wasn’t going into the fuel tank.

The boater saw a fuel sheen on the water and noticed the boat’s fuel gauge hadn’t responded, said Tim Clark, a Coast Guard operations specialist. Instead, the bulk of the fuel collected in the bilge at the bottom of the boat, Clark said.

There didn’t appear to be a leak in the tank and how the fuel wound up in the bilge was unclear, Clark said. Clean Harbors, an environmental cleanup company, was at the marina on Front Street Saturday night to pump out the fuel and tow the boat to a service dock.