pontoon motor mount

My father in-law and I are restoring an older pontoon boat and want to change the outboard motor mount. The boat is 25' and is rated for a 115 hp motor. The current set up has an 80 hp mercury and when you rev up the merc the current motor mount digs into the water and throws it up everywhere. It is a strange mount that even includes an adjustment arm where the whole mount can be manually raised or lowered. But the front of the mount is "square" to the water digging in several inches and this can't be an efficient setup.

My father in-law is a metal worker and wants to make a new motor mount for the boat. We have noticed that newer pontoons boats (ours is 20+ years young) have tapered and or v-d motor mounts so that the part of them that is in the water will give the boat lift and/or cut waves. Since we are doing this custom we want to incorporate the most advantageous design. I can't find any specifics on motor mounts with internet searches so does anyone out there know where we can hone into such information or have advice for us? Thanks in advance for your response.

kc

 

What you're doing- looking at newer, more advanced boats- is a good start. I'd take a good scale drawing of your boat and work from there to sketch in the new motor mount, making changes as you see things that might work. It's a pontoon boat; it has crappy hydrodynamics to start with and from what you describe just about anything would be an improvement. There's probably a pile of equations and rules and a 600-page book on pontoon boat design somewhere; if I were you I certainly couldn't be bothered to go to all that trouble. Try asking some pontoon builders and owners of different boats to see how they like their boats' behaviour with different shapes.
Happy boating,