However major disadvantages are how they affect the attitude of the craft, vulnerability to being swamped, difficulty to service or repair on the craft, theft and vandalism, that until the event of the four stroke version, noisy and smell and reliability were significant factors.
Of course there was the inboard / outboard which was initiated by Volvo and then by the major outboard manufactures. Their point was that the engine could be put anywhere along the lubber line and so related the
engines weight to the craft's attitude. Ease of fitting and the fact that the propeller's position close to and below the gear box negated the need for space and long shafts were other advantages.
It was these issues that coursed my mind in developing the engine box. Although I haven't researched it I can't imagine for a moment that its particularly new. I have been on and seen small sailing craft where an outboard has been on pinioned lift on the transom where it could be lowered and raised as needed and also
where portal in the counter has been made to drop and accommodate an outboard. In both however exposu re to green water, general slop and driving rain made them vulnerable.
I suppose it would be germain to define 'an engine box' at least in the terms that relate to my boat.
An engine box is a delineated confine for an outboard to enable its easy movement in and out of the water below the craft and facilitate and ideal retracted position which will maintain a low centre of gravity, be able to be stabilised, and provide good exposure for fresh water flushing ( a good discipline ), maintenance and repair. Inevitably the outboard should be one whence that exhausts through the propeller but 'bleeds' on some engines will mean a diversionary pipe to take the exhaust to the bottom of the well. Similarly, the egress of water from the engine needs to be diverted somewhat from the spout that throws the water laterally from under the engine cowling. Of course this is really a directional issue as long as this is down into the well and, importantly, vitally in fact, can be seen.
Arrow 1. indicates the usual exit for engine water. Here, in a functioning position, water would be filling the boat over the top of the engine box but has been rerouted in the cowling to arrow 2. where it will be well down in the engine well but above the cut-off seal and therefore easy to view at any time.
An exhaust bleed at arrow 3. would exit fumes into the boat, normally these would be going aft in the wake of a boat, and have been rerouted to exit at arrow 4., where an aluminium spigot accommodates the yellow re-routing tube seen in the picture below. At this level it is below the cut-off seal.
I chose a long shaft outboard to give me the broadest scope for manoeuvring the parameters for designing
the engine box and fit it into the boat.
At the outset it was one of my hopes, allowing that the boat goes through the water well, power on - power off, that it should go well under sail. Therefore a low centre of gravity for the retracted engine was quite high on my priorities as well as bringing its ballasting component forward where the bulk of the buoyancy in my boat's design lay.
In the absence of CAD I made full size mock up of the engine profile in thin ply and using this with thin battens worked out a the profile that would allow vertical lift of the propeller and subsequent forward incline of the engine.
The profile of the engine in the retracted position. The fine clearance of the propeller at the left margin (representing the aft limit of the engine box) shows easily.
The profile being rotated down shows the flanges on the front of the shaft casing touching (bearing on) the
slippery dip profile of the box. The rectangular section, centre right , the would be transom in a normally situated outboard, has now moved up and backward.
The engine has now entered the water with its cavitation plate a couple of centimetres below the bottom of the boat represented by the bottom margin of the background sheet.
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