No need to block anything. Build a small whale tail out of aluminum to channel the water to your intakes, it will also help greatly with hole shot. I'm not talking about those hideous white monstrosities they sell. Build it something like this, BUT, extend it further forward to catch more water. We built them to extend in front of the gear case. It does not slow boat speed and yet improves hole shot and helps channel cooling water to the intakes. We also bend about 1/2" of the sides 90 degrees down to hold water. The old 2 stroke tohatsus had terrible cooling systems. I'm glad they improved them on the 4 strokes, mine pumps over 20 pounds of pressure.
