My family owned a Yankee Seahorse in the 1970's. It had a yellow hull color and was a great quality boat, extremely sturdy and rigged with oversize hardware. Designed by Robert Finch, the boat went into production in 1972 by Yankee Yachts in Santa Anna, California, aiming at the 1/4 ton class of racers. Most of their boats, the Dolphin 24, the 26, 30 and 38 were Sparkman and Stephens designs; the Seahorse and the 28 were Robert Finch designs. The owner of Yankee was John Schumaker, whose name is also on many of the sails of those yachts.
We sailed our boat on Saginaw Bay of Lake Huron and sadly sold it after I was done with college and my dad lost his deckhand.
Now, nearly 35 years later, I have purchased a Yankee Dolphin (hull #204). It is interesting that the cabin is a mirror image of the Seahorse, that is everything is on the opposite sides, but otherwise nearly identical.
If you have any questions regarding the Seahorse, my memories are pretty sharp of all the rigging having sailed it for several seasons by myself. Good sailing and I would like to hear more about your boat!