I didn't find a definite answer online, I've found a few speculation posts. Supposedly this motor was made by Yamaha(99-04ish), the block, power head and exhaust are the same as the 15, only different being the carb. I literally bolted on the new carb and it fired right up. I found out the newer 4 strokes are much smaller and the 8/9.9 share everything. Mine is the 115lb motor, new ones are mid 80's.
Everything I could find in the mercury parts catalog showed the same except carb and prop.
I went out tonight by myself and my normal gear, 18mph is the max I saw, tach shows 5600-5700. Pretty happy with the results, at least at these speeds it feels like I'm getting somewhere! I didn't mess with the trim yet, it's on the middle hole.
Everything I could find in the mercury parts catalog showed the same except carb and prop.
I went out tonight by myself and my normal gear, 18mph is the max I saw, tach shows 5600-5700. Pretty happy with the results, at least at these speeds it feels like I'm getting somewhere! I didn't mess with the trim yet, it's on the middle hole.