WARNING! Always perform any tuning trials on protected and uncongested waters. More extreme tuning trials should be performed with appropriate safety gear and a support boat. Never exceed your driving skill levels.


Engine Height and Trim



Note: Propellers have sharp edges. Always use care when handling. Dropping a prop can bend and damage blades causing poor performance.

There are a few things you can do to any prop to peak it's performance. The most basic is to make sure it's clean, and all the blades are straight and even. If there are pitch inconsistencies between blades no amount of additional tuning will be of benefit. Aluminum props are often inexpensive to simply replace, and then you'll have an emergency spare. Stainless and higher end props (not composite props though) can be reworked by your local prop shop to match up the pitch, as well as balance or custom tune your prop.

The next step is to clean up the leading edge. Stainless props should have a sharp leading edge (the edge that cuts through the water first). If it's dinged or blunt use a fine metal file to clean it up. Remove material from the back of the blade (side facing the front of the boat) whenever possible. Follow up with fine sand paper or emery cloth. The following edge should be blunt and square. Be careful working around or on this edge as it may be intentionally cupped or cut away.

Aluminum props should have rounded leading edges. Many come from the factory with a flat and two sharp corners on the edge. Use a fine file to round the edge out gently, removing only as much material as absolutely necessary. Follow up with fine sand paper or emery cloth. The following edge should be squared off with good sharp corners. If it's not you may still not want to adjust it because you may change the blade shape, or remove any intentional cupping.

WARNING! If you remove much material from any or all blades, the prop may need to be rebalanced. This can rarely be done without the professional equipment of a prop shop.

The next level of prop tuning is to polish it up. The most important side is the blade front faces, which is the side facing aft with the prop mounted on the outboard/boat. If you have an aluminum prop with paint that's peeling or inconsistent gently remove it. It may take a scotch brite pad, careful use of a razor blade, or polisher with compound or abrasive grit. A paint stripper chemical can also be used. If so keep it away from the prop hub, as it can attack the rubber insert and render the prop useless. If the paint is even and intact it can be left. The simpliest way to polish up a prop is to start with fine wet sanding, followed by hand rubbing with steel wool. Aluminum props rarely benefit from any higher level of polishing. To polish stainless use a cotton buff on a bench grinder with an appropriate compound. You may want a chrome shine, but some offshore racers have also found a matte polish to actually be faster.

Have an aluminum prop? Try upgrading to stainless if available for your engine. Stainless props have thinner blade sections than aluminum while still maintaining strength for reduced drag. Stainless is more likely to have cupped blades. They can increase speed depending on your engine load/rpm at WOT. Cupping can also reduce the chances of the prop blowing out/ventilating while cornering allowing the prop to be run shallower. A shallower prop reduces gearcase depth and wetted surface area, therefore reducing drag. Stainless props may also have blade shapes more optimised for supercavitating operation like common on small outboard props run at high rpm.

Other options include changing to a prop of different diameter or pitch. If you're running a lightly loaded boat a 3 blade prop is generally best. Keeping towards the upper end of the normally recommended pitches for your engine should yield highest top speeds and acceptable holeshot performance. If you're outboard is running near or above the top of the manufacturer's recommend RPM range at WOT, you should consider increasing your prop's pitch. You can buy a more aggressive prop, or your local prop shop can pitch it up a little.

A boat run with more people or gear, or in rougher weather, may benefit from increasing the diameter or number of blades for a better bite on the water. You'll also want to start on the lower half of the recommended pitches for your engine. If you engine is already at the lower end of the full throttle RPM range you'll have to step down in pitch at the same time. Reducing pitch tends to reduce boat top speed or increase engine WOT rpm. On the contrary, if your engine is at the top end of the RPM scale recommended by the engine manufacturer you might gain top end by increasing pitch. Keep in mind that if you're already in the rpm range, increasing pitch will slow holeshot times, while reducing pitch will improve acceleration.