Boatbuilding Blog

June 16, 2007

Motor Well Planning

Filed under: Building - Before Flipping — tomlarkin @ 12:45 pm

The plans call for an inboard diesel but I’m going to use an outboard instead.  Diesel fumes – both exhaust and raw fuel – make Meryll sick. Also, removing the motor from the center of the boat adds interior space and isolates the noise and fumes away from the living quarters. Not to mention that installing a motor looks like hard work! Another factor is the prop shaft through the keel adds at least an additional foot of draft that I can avoid with an outboard. I want to take this boat in very shallow water and beach it on sandbars once in a while.  See the ‘Twin Keels’ entry for more detail.

The decision to make the motor completely inside the motor well was easy – I didn’t want to make a huge hole in the stern! I think the round stern is one of the most beautiful parts of the boat. Therefore I had to mount the motor forward enough to be able to kick up inside the cutout. The cutout dimensions I ended up with were 18 x 40 inches. I have some half-baked ideas on how to mount a kicker in-line with the motor but I won’t be able to see if they will work until the boat is right-side up.

To start the planning I mocked up a motor well on the back of my runabout in the driveway. The runabout has a 45 hp Honda four-stroke. I’m planning on using a similar (or maybe even the same) motor on the Godzilla. 

Motor well cutout planning.

Once I had minimum dimensions, I laid out various plans on the bottom of the boat in blue tape. I had to make the cutout and install the sides of the well before I glass the hull, so I couldn’t put this step off.

Stern layout marked with painters tape.

Once I had the plan I wanted I cut a huge hole in the bottom of the boat.

   Hole in the bottom. 

Then I realized the prop wash would splash inside the well so I made the hole even bigger!  I glued in the sides of the motor well and called it a day. The cross-bar is just to brace the plywood while gluing. The small hole on the centerline of the bulkhead is on the waterline. The draft at that point is about six inches.

Big hole in the bottom.

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1 Comment »

  1. […] Filed under: Uncategorized — tomlarkin @ 10:38 am Three years ago when I was designing the outboard motor area I used my Honda 45 HP as a model. I made a full-size copy of the motor out of foam and designed the […]

    Pingback by Motor Mounting « Boatbuilding Blog — April 29, 2010 @ 10:38 am


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