for some strange reason :notam: most companies have a biased against shorter boats. Some of them draw the line at 26.' They prefer a longer boat for high H.P. applications. They consider 500 HP too much. (even though we don't )
Thats not to say that getting insurance on a 27' is any easier.
I found it difficult to insure my 25'
I know some of these guys use an insurance guy in L.A. Hopefully someone can help you out with his phone #.
Otherwise contact Markel and Progressive.