High-Speed Longtail Mud Motors
Rule #1: Decrease Weight
Get your load (boat, motor, & person) as light as possible and distribute it evenly throughout the hull for proper planing.
Rule #2: Narrow is Better
The bottom width needs to be as narrow as possible. A long narrow hull will always be faster and more efficient than a short wide hull with the same horse power engine.
You’ve made everything as light as possible, and have a narrow boat that you feel comfortable riding in. Now onto choosing the proper engine.
High RPM Engine
Revolutions per minute (RPM’s) is how many full rotations of the crankshaft occur in your engine, in one minute. In simple terms for longtail mud motor use = how fast your prop is spinning. It is a 1:1 ratio for engine crankshaft rotation to prop rotation.
To achieve high speed with a longtail, you need an engine that spins fast. A stock single or v-twin engine is normally governed at 3,600-3,800 RPM’s. We need the RPM’s to be at least 6,000 to be able to use the SPS Racing Props.
The racers in Thailand use 2-stroke engines that spin at 8,000 to 10,000 RPM’s and they use some of the same props we have in our store to achieve racing speeds.
Right now there are two approaches to reaching those kinds of RPM’s
Modified/Upgraded 4-stroke Engine
- More expensive option
- No longer a stock engine. Less reliability.
- Can get up to 7,500 RPMS
- Fuel type is gas
- Examples of engines used: Store bought stock engines (Predator, Honda, Briggs, etc…) that you upgrade yourself, or pay someone to upgrade the engine for you.
Re-Purposed 2-stroke Engine
- Less expensive option
- Stock engine. Stays reliable.
- Can get up to 7,500 RPMS or more depending on engine
- Fuel type is mixed (gas & oil)
- Examples of engines used: PWC (jet-ski) engines, Rotax engines from planes or snow machines.
You have a narrow boat, everything is as light as possible, and now you have an engine that is reaching the proper RPM’s. Now to choose a propeller.
High Pitch Propellers
At Swamp Runner, we have two categories of high pitch propellers:
- Less expensive
- Unique, but still produced in great quantities
- High pitch when compared to Hurricane or Standard props
- Taper of propller hub fits our standard shafts
- More expensive
- Unique – not mass produced like standard props
- Very high pitch on the blade of the prop
- Taper of propeller hub only fits SPS Racing Shafts
- Bullet Props – The Bullet props come in a uniform, set size and pitch. So if one is too big, you can step up/down to the next size.
- Racing Props – We offer a wide variety of racing props, produced by different foundries, with custom diameters and pitches.