I just replaced the Tohatsu 2-stroke on my '93 23.5 with a 2004 Honda 9.9hp 4-stroke (Electric start, long shaft). The motor was new but run 4 hours by the dealer in their break-in tank. Really runs nice and moves the boat well. However, as the boat gets over about 5 kts, water begins leaking/shooting out of the seam between the upper and lower cases on the motor. I tried running up the rpm at the dock with the motor in neutral. The tell tell stream increases in velocity as you would expect, but no water comes out between the cases in that situation. It seems to be dependent on the speed of the boat. One thought I had was that I may have the motor a little too low in the water. I think that Honda vents exhaust gas on the front side of the shaft when in reverse and it may be that the water flow at over 5 kts is enought to push water up the lower case and out the seam? I lifted the upper case and had no water up there. Anyone with similar experience with the Honda. I'd like to make sure I'm not hurting anything when that is going on.