"We didn't know there was so much involved we 'assumed' it was going to be like a car. "
It IS like a car. No safety classes? Surcharged. Going to Canada or Mexico? Surcharged. Driving too many miles? Surcharged. Commercial use? Surcharged. Bad credit rating? Surcharged. Gross weight over 20,000 lbs? Ooops, commercial license, surcharged again.
Cars, boats, doesn't matter, the insurers have surcharges for everything. Pick a slow time of a slow day, like midweek late morning or midafternoon, and pick a broker's brains. Then do it again the next week, with someone else. One of them might even earn your business.