Sea-Trial Guide For Propeller Buyers
Thinking of new propellers? For optimum propping, provide the prop shop with data based on the boat's performance as currently propped. To gather this, start with a clean bottom, normal load and half-full fuel tanks. At each 400 rpm for gas or 200 rpm for diesel (recorded twice, on reciprocal compass headings), note speed and running angle (buy an inexpensive clinometer), plus electronic engine load and/or fuel consumption (exhaust gas temperature is ideal on mechanically governed diesels). Use one tab/engine trim setting through all rpm; if the boat requires multiple trim settings, note what they are at each rpm. Record wind, sea and current, and mention anything that changed the boat's windage, weight or balance from original — hardtop, extra generator aft, all-chain anchor rode, etc.