Home › Forums › Bass Cat Boats › Question about running on pad
oldtimer57.
I have a quick question regarding running on pad. When my Sabre hits 4200 rpms, there is a very distinct change in the attitude of the boat as it pops up onto the pad. When I am running light by myself, it is a very significant change. Right as it pops up, the prop seems to suddenly hook up and the motor drops approximately 300 rpms. I was just curious as to what is happening during this transition that causes such a noticable pop. Are you reaching a point where the lift of the hull overcomes the friction of the water or does it have to do with air being compacted under the hull which frees it up? Im not looking for a trade secret, just a general explanation of what happens at that point during acceleration. Right after it pops up, are you running at the most efficient speed? Yes, I am a bit bored today.
Hi AL Chris, There are a couple of questions you have here. Ill try to answer them by going through each step your boat is going through from stop to full-pad running. When you hit the throttle from a dead or rolling stop, exhaust gases vent through the holes in the prop hub just forward of the front edge of the prop blades. These gases mix with the water and allow the engine to rev high, which gets the motor into its powerband. Then, as the boat comes out of the hole and gets on plane, the exhaust gases then vent mainly through the hub (path of least resistance) and the blades on the prop “bite” the water fully – thus the decrease in rpm you notice. After the boat gets on plane and you begin trimming the motor up, the angle of the motor starts to lift the bow, which allows air to get trapped underneath the hull and acts to lift the hull out of the water. It is at this transition you notice a definite increase in speed (less of the hull is in contact with water – decreased friction – and a drastic change in handling. This is not just your boat but any boat that runs on pad. As far as the most efficient speed in which to run a boat, that would be on pad. The reason for this is because the less water contact the hull has, the less friction there is and the motor can push the boat more efficiently. I hope this helps. TerryTerry Battisti
Thanks for the information Terry. So the boat jumping on pad is a result of air being packed under the hull providing additional lift. I can be crusing at 4000 rpms and give it just a touch more gas and it feels like a fat person sitting down on one end of a seasaw. I was just curious about the physics in play during than transition. Thanks for the explanation.
AL Chris, Thats part of it. The motor and the air are lifting the bow. The motor wants to run level and in order to run level, the bow lifts. When the bow lifts, it allows air to flow under the hull and that again adds lift. You can test this yourself by not trimming the motor while running full throttle. At full throttle without trim, the hull stays glued to the water. Begin trimming the motor and the bow begins to lift. Then, at that critical point (around 4200 rpm you say) the motor and air combine to really increase the lift – as if I were sitting on your stern. lol. TerryTerry Battisti
Most boats that I have driven have three distinct phases they run in. The first is displacement mode, where the hull is plowing thru the water and consumes a ton of horsepower to do this. Then the hull pops up on plane and now you have the rear of the boat contacting the water, generally from a point about 6 – 8 from the transom back, and all the way out to the rear corners of the boat. This is pretty efficient in that you are now displacing little water. The final phase is when you feel the boat “rise up” a bit more and run on the pad with the rest of the bottom out of the water. Now you have 4-5 of the pad in contact with the water, with air being trapped under the hull to keep the sides of the bottom out of contact with the water. This is where the boat begins to feel “loose” and is where you will begin to see chine walking since the corners of the boat are no longer in contact with the water. This is the most efficient phase since you have miminal drag with minimal wetted area. Some boats are more efficient bow-high. Some are more efficient with the bow down so that it traps air underneath the hull. Best way to determine which is which is to use the tach and GPS speed…2008 Pantera Classic2014 Mercury Pro XS 200
© 2026 Bass Cat Boats
