Many recreational propellers generate around 10% slip at full speed while high-performance propellers on very fast boats are closer to 6 or 7%. The table below generally defines the terms. There are so many factors that affect boat speed that it is hard to make accurate estimates of what the real top end will be. Shaft horsepower is to be the actual uncorrected engine horsepower less drive train losses. The positioning of the electrode gap is important to the proper operation of these high-tech low-emission outboards.
These two characteristics apply to the planing hull. You can plug these results into the formulas on the page or use our and come up with a propeller pitch. Whether trying new props, changing the boat and motor set-up, or by re-distributing the load, a go-fast boater is forever reaching for that last mile-per-hour of speed. Catamaran hull speed, trimaran hull speed and light displacement hull speed may be higher. P art's at central warehouse, you'll get it next month. To help choose a good all-around efficient prop, run the numbers at both full speed and at your cruising speed as some propellers are great for top end but are not very efficient at normal speeds. These props feature interchangeable allowing them to fit a wide variety of different motors at an affordable price point.
We have found manufactures published weight to be unsuitable for these calculations. Boat Speed Predictions Please note - by using this calculator you agree to the following license provisions: This calculator is for non-commercial use by the general public only. Contact the designer manufacturer to find out what the vessels maximum is. Find All propellers that fit your engine You will need to know your engine manufacturer, model or horsepower to determine which propellers will fit your boat. It is impossible to pick a perfect prop for every hull and situation. The information, software, products, and services published on this web site may include inaccuracies or typographical errors. The is a simple formula for calculating displacement boats speed which is typically 1.
Step 4: Select the Model of your engine. By using known values for the weight, power and speed you can come up with a more accurate constant for your boat. Gear ratios vary between manufacturers, between the engine models of each manufacturer and between High Thrust and regular gear ratios. Note that this number only applies to Hull speed, as calculated here, is important as it is a building block to attaining figures like, what power is required and ultimately calculating what propeller may be optimum for a particular boat. Marine Propeller Calculator Marine Propeller Calculator This requires the use of enabled and capable browsers. Enter any 4 variables and the 5th variable will be calculated.
Once you provide the specifications on your engine, we will display all of the propellers that fit your engine. Hull Speed Chart The chart displays speed at different percentages of theoretical hull speed. Adjustments of -5 to -10% of corrected dyno figures are typical. The important thing here is the length of the wave is relative to the length of the boat. Divide this result by the pitch of your propeller. The Mercury Racing Prop Slip Calculator below lets you quickly determine propeller slip.
You will then be able to filter based on diameter, pitch, material, of blades, etc. For a displacement hull it is pointless to try go beyond hull speed. Using the calculator in this fashion will produce surprisingly accurate results. This calculator is designed to give any missing value from the 5 variables needed for marine propeller calculations. Have someone rotate the propeller while you shift the motor carefully into forward gear.
This is the maximum speed you require and should be less than the calculated hull speed. The results and the chart plot are based on an of 1. Note, there are other factors, such as safety, not covered by this calculation that would limit desired speed. Note that engines are rated differently for inboard diesels. Note that engines are rated differently for inboard diesels.