Pokey, When I ordered a 2006 tug there were only two options, the 20HP and 30HP. I am sure you could call the plant at (253) 839-5213 and John Livingston (owner) can answer your question. They were good to answer anytime that I called. They were one of the most customer friendly companies that I have ever dealt with. It seems that I have seen something about a 27HP at one time and it may be that Yanmar has made some engine changes in that time frame.
Ron