Most boat buyers compare hulls by length, width, and deadrise. On an inboard jet boat, there’s a more important question: how well does the bottom feed water to the pump?
A jet pump can only push the water it gets. If the intake is starved or fed air, the boat loses grip, cavitates in turns, and struggles to get on plane. That’s why we build our inboard jet hulls with a radius bottom and a delta pad. Here’s what that means and why it matters.
What is a radius bottom?
A radius bottom has a gently curved bottom rather than a sharp V. On our Fastwater models, it’s a 14-degree tapered radius bottom. The curve carries the boat smoothly, and the shape flattens out toward the stern where the jet intake sits.
What is a delta pad?
A delta pad is a flat, triangle-shaped planing surface built into the bottom, just ahead of the jet intake. It does two jobs:
- Lift. The flat pad gives the boat a strong planing surface, helping it climb on plane quickly and run shallow.
- Clean water to the pump. The pad presents solid, unbroken water straight to the intake. That keeps the pump loaded in a straight line and in hard turns.
Every one of our inboard jet hulls gets a delta pad.
Why not a deep V?
Deep-V hulls are great in big chop, and on a prop boat they make a lot of sense. On an inboard jet, a deep V carried all the way to the stern works against the pump. A V pushes water outward, away from the centerline, right where the intake needs it. In a hard turn, the boat leans and the intake can lose water or suck in air. The result is cavitation and a loss of steering just when you need it most.
The radius bottom and delta pad solve that problem by design. The pump sees clean, well-packed water in every condition.
The honest tradeoffs
No hull does everything. Here’s how the two approaches compare:
| Radius bottom with delta pad | Deep V carried aft | |
|---|---|---|
| Feeding the jet pump | Excellent; clean water to the intake | Can starve or aerate the intake in turns |
| Shallow-water running | Runs and planes shallow | Draws more water |
| Getting on plane | Quick, even when loaded | Needs more power |
| Efficiency | Strong | Lower at the same power |
| Big chop | Firmer ride | Softer ride |
We build for rivers, bays, and the work our customers do. For those conditions, keeping the pump fed beats the softer ride of a deep V. If most of your time is in open water and rough chop, our Coastal Series uses a full-V bottom built for big water, and it’s available with an inboard jet or outboard power. We’ll help you weigh the tradeoffs for how you run.
Built strong where it takes the hits
The back of a jet boat’s bottom takes the most abuse. It’s where the boat lands, where rocks and gravel hit, and where the pump intake sits. So we reinforce it.
We add a 0.250-inch doubler plate to the bottom at the transom, running six feet forward. That brings the aft bottom to 0.500 inches total. And the whole hull, bottom and sides, is 5086 aluminum, fully welded over a box-girder structure.
Frequently asked questions
What does a delta pad do on a jet boat? It gives the boat a flat planing surface ahead of the intake. That adds lift and sends clean, solid water to the jet pump, so the boat keeps its grip on plane and in turns.
Why do jet boats cavitate in turns? Usually because the intake loses water or pulls in air as the boat leans. Hull shape near the intake is a big factor. A delta pad helps keep the intake fed.
Is a radius bottom good in rough water? It rides firmer than a deep V in big chop. In exchange, it runs shallower, planes faster, and feeds the jet pump better.
Do all Rogue Jet boats have a delta pad? All of our inboard jet hulls do.
How thick is the bottom at the stern? We add a 0.250-inch doubler at the transom running six feet forward, for 0.500 inches total in that area.
See it for yourself
The best way to understand a hull is to ride in one. Call us at 541-826-5400 or send us a message to set up a visit. Want more background? Read about inboard vs. outboard jets and how shallow a jet boat can really run.