Can I Install a Larger Propeller and Pick Up More Speed?
Question #1: How do I select the correct gear ratio and propeller combination when upgrading my current product?
Response: There is no basic answer to this question while the reality is that nothing replaces having good data to review when making selections. No matter how much estimating and calculating is done, nothing will replace having hard facts on how the existing boat performed with a known setup in known conditions. Therefore here is the approach we recommend following.
The best approach is to use data collection of the EXISTING ENGINE/DRIVE/PROPELLER COMBINATION
1. Record the gear ratio and serial number of the current engine and sterndrive.
2. Record the pitch of the current propeller.
3. Note the condition of the engine. If you know the engine is not currently making the correct level of power this affects the data going forward.
4. Record the maximum speed along with the maximum rpm achievable with the existing setup. Is this recorded with a GPS or the standard speedometer on the boat that may not be 100% accurate?
5. Note how the boat is loaded when recording this data. Is this the normal loading condition for the boat? For example do you normally operate the boat with only 4 of the maximum rated 12 passengers on board? Do you normally fill the fuel and water tanks every time you use the boat? You have to make the choice of how you want the “performance penalty” of weight to be factored in. It could be that you want to make your choice based on running in the worst case loaded condition even though this happens very rarely, simply because it will allow you the opportunity to run at this worst case loaded condition when it happens without damaging the engine. Otherwise if you set the boat up for maximum performance/speed being configured around the lightest case loaded condition (which happens 99% of the time) you will get the best performance however if you do operate in a heavy loaded condition repeatedly or for an extended period of time it may cause damage to the engine. READ MORE on how this engine damage actually occurs.
Tags: gear ratio, prop selection, propeller