The less of your hull that touches the water, the less drag and the higher speed. But
with too little hull in the water, the boat will become less stable and could overturn. If
there is too much hull in the water so the bow (ie the front) is running low, the boat is
said to be running "wet". If the boat is too light on the water with only a small length
at the back in the water, it is said to be running "loose".
Angling the prop up will lift the front of your boat generally resulting in less hull in
the water and faster speed. Angling the prop too high though will cause instability and
the prop may "ventilate" or spin without gripping because it's too close to the surface.
Angling the prop down will lift the back of the boat and keep more hull in the water
generally giving more stable running but with less speed.
Trying different prop angles will find the one that works best for your boat in different
water conditions. To start with, run a straightedge along the bottom of the boat
projecting out the back, and set the strut drive unit so the prop shaft is parallel with
the straight edge.
When adjusting the strut, you may need to also slightly change the angle of the
stuffing tube. If you do need to slightly rebend that, do so very carefully with the flex
shaft inside the tube to minimise the chance of making too sharp a bend.
Step 7: Tuned Pipe Performance Tip
Tuned pipes boost engine power by using the pressure waves generated by exhaust
gases to literally pull more fuel into the cylinder. However, to achieve this, it is
critical to have the right length for the exhaust gases as they travel from the exhaust
flange to the "belly" of the tuned pipe (that's where the pipe is at its widest diameter).
For our billet XP254M engine, this distance is between 370 and 390mm which needs
to be measured along the centre line of the exhaust including the header pipe, as
shown in the diagram. Having either a longer or shorter length will reduce the
engine's performance.
