Upon
taking the boat out of the water I noticed a frothy (brownish) oil and
water mixture leaking out of the exhaust ports and the water ports.
Any ideas?

Two ideas,
Water in the gas
Leaking water jacketless likely
I suppose it could just be a weak cylinder, misfiring for all the usual
reasons, filling the exhaust channel with unburned fuel.

Start with the garden variety tuneup, plugs, compression, timing, carbs etc.