Opt for Sony SRS, Braven BRV-1, or Braven Balance as these are the loudest waterproof speakers as per gadget reviewers - louder than the noise of a running diesel engine.
Kubota R510 Wheel Loader + Cab and backhoe, JD 6200 Open Station, Cushman 6150, 4x4, ten foot 56 hp Kubota diesel hydraulic wing mower, Steiner 430 Diesel Max, Kawasaki Diesel Mule, JD 4x2 Electric Gator
I worked for a large sound company, doing factories, stadiums and airports. I remember they used to scotchguard the paper speaker cones to make them water resistant.