Puzzler: Which 4 stroke will fit in my sailboat well?

[closerhauled]

I have a '32 sailboat (Kettenburg PC) racing sloop that has a well in which an outboard can be placed. It displaces about 4500 lbs; has a full keel. The openning that the lower unit must traverse when it is placed in the well is fairly small (about 5" wide and 9" long). I've used older OMC product 6 and 10 horse 2 cycles, but can't take the noise and exhaust anymore! Which 4 cycle (Honda 8?) would have a small enough anticavitation plate to fit the well? <br /><br />thanks in advance!