clawman wrote: took the advice of steps + others + got a 13.5 inch x 16 prop for the aqualine now do 4000 rpm for 40 km per hour instead of 4800rpm. couldnt test wot as too rough at mana tonight. also the motor does sound a lot better too. shame i didnt do this 250 hours ago or the dealer a bit more proactive
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Steps wrote: You'll always get better performance out of stainless, better holeshot and prop will allow better trim without cavitation and porpoising due to blades not flexing as much SS props come into there own with very high powered or bigger heavier boats....when moving at higher speeds. There is little if any difference between a alloy and stainless on boats upto around 1300 kg at cruise speeds... as there is not emough loading on the blades to cause distortion. For general use boats, the extra load on the blades at hole shot is so quick and over the bow wave to have any significant noticeable difference....The add into the exhaust thru the prop , designed to cause slight ventation on hole shot, in the same manner as a hi stall torque converter to get a drag car motor upto higher rpms and power band, then grip. As to porpoising, it is rake that influences that, not blade twist... the fact that to sorce a high rake, usually 4 blade prop, the only source happens to be SS doesn't mean SS is better for preventing porpoising If one takes a general use boat around 1200/1300kg and 115, 140 and 150 hps compare 2 identical props, alloy and SS, collect accurate data. There is very little difference up to around a 35mph cruise, slightly more but still not noticeable or significant in data, hole shot to 35 mph... Getting upto 37 mph fast cruise and to WoT, with the extra load on the blades then one sees an increase in change, MAY feel notiable if look at your odometer and rpm gauges as the pitch decreases.. and a slight increase in fuel consumption. lighter boats where far less loading, and smaller diameter props used, nothing noticeable. Getting up around 1500/ 1800 plus 5.8/ 6m boats that have larger diameter props (14 1/2") and blades loaded up it is then cruise speeds, performance and economy etc becomes significantly noticeable. Selling SS props is rather profitable , espec when not really applicable.. |
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