A Tunnel hull setup is made up of only one unit that controls and supports all adjustments. This unit consists of the Motor, Drive line, all as one unit. It is commonly referred to as the Outboard motor assembly.
Outboard Motor Assembly
There are a few select Outboard units available today specifically for a Tunnel Hull. Most are best used with 4s LiPo and a motor that will spin a prop smaller than about 42-45mm to clear the aeration/cavitation plate. For larger setups it is possible to put together a custom motor mount for a 7.5cc or 11cc Outboard lower unit.
Setup an Outboard
When mounting the Outboard Unit on a Tunnel Hull, it is important to determine the final position the Outboard Unit will be setup in, for the first initial run. This is due to adjustments that can be performed to the Outboard Unit for fine tuning. The reference position for the Outboard Unit, and this will also be the first run position, is where the center prop line of the strut is even with the furthest bottom surface or edge of the sponsons. This will be the reference position and first initial run position. When mounting the Outboard Unit it is important to allow adjustment room for raising and possibly lowering the unit on the Tunnel Hull. Allow 60% of total adjustment for raising the Outboard Unit. Keep in mind when raising the Outboard, the screws will reach the bottom of the adjusting slot as the screw remains stationary and the slot slides up. Allow the remaining 40% of the total adjustment for lowering the Outboard. For example if the Outboard allowed exactly 1” of height adjustment, 0.6” would be for raising the Outboard and 0.4” would be for lowering the Outboard. Prop shaft angle should be set to 0 degrees or neutral for the first initial run of the Tunnel Hull. Refer to the drawing below for a better visual of the Tunnel Hull Setup.
Center of Gravity on a Tunnel Hull will be 25-35% of the total wetted surface Hull Length.