Converting from Inboard to Outboard

[Ray Suarez]

First thanks to all that provided info in trying to resuscitate my D7. I have given up and have decided on an outboard (primarily for cost reasons).

Mostly, I need the engine to go from the mooring to the dock (100 yards) to pick up the kids. Also, I have the boat near the Hull Gut in Ma. Currents can go up to 4-5 knots depending on the moon, my D7 at full throttle would at times not allow me to get thru and force me to coordinate with tides.

I am thinking of purchasing a 2 stroke - Merc 9.9 OB with a 25 inch shaft. The estimated cost is about $2,200 with the shaft extender. And about 150 for the motor mount. Sound reasonable? I am also open to other OB's.

My primary concern is that the transom will be able to support a 9.9 OB engine on an engine mount with out flexing. I heard that 7.9's with no original inboards had additional support in the transom to support outboards. Is this true (and is mine inherently weaker)? I have thought about putting a 3/4 inch piece of marine plywood on the inside to spread the load across a larger portion of the transom. However, I am concerned that the plywood will compress over time and force me to continue to tighten the mount. Do I need this extra support?

Any advice on installing the engine mount. What kind of compound should I use to seal the holes made by the thru bolts? Also, do I need a special gasket between the hull and the motor mount?

As for removing the old diesel. Thoughts on plugging the shaft hole and removing the strut holding the cutlass bearing would be greatly appreciated.

--ray
raymond.suarez@veritas.com
ray.suarez@bostonlight.org