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MATT, here's my guess... two 540 9L are too small for a 41" cat and have a too high of a KV for a 51mm prop, you can't reasonnably go above 4S because Feigao's are rated for 50000rpm max (70K with BOCA ceramic bearings), in fact they are not limited to 4S, I had some email exchange with Feigao direct, they confirm the max voltage is 32V, but depends on the KV as long as rpm does not exceed 50Krpm with stock bearings!
No this boat is design for 26CC gas engine, some moded 26CC Zenoah engine can produce almost 5HP (3600W) and the very best are given for 6HP, that said you need to have some bigger motor to go fast, that's just my point of view but... two 580 under 6S would be certainly better, the bigger the hull is, the higher cell count you want to have in order not to pull very high amp! Take it this way... let's say you need 3000W to move that hull fast, under 4S that's 202A
(so 101A per motor as you have 2) under 6S that's "only" 135A total so 68A per motor, much more reasonnable isn't it?
You could go for a pair of 540 10XL unders 6S but these motor are rated for 66A (not max but at their best efficiency) so there no room for playing, I personnaly try to use the Feigao at 80% of the max amp because this is the constant amp draw required but burst (at startup) it'll pull at least 80A! If you go for a pair of 8XL that are rated for 83A, because the KV is too high, you won't run 6S no way even with a 42mm prop (that's what I use on my 29" mono under 4S), and you can't reasonnably and efficiently pull 1500W out of a 540XL motor, you need to go for a bigger baby!... 580L!
Talking about Lipo's now, according to the above explaination, if you need 68A constant per motor and probably 90 or 100 burst on 6S pack, some 5000mAh 20C/30C can do it, 20C means they can supply 20x5000= 100A constant, 30C is the burst amp rating. but if you can go for higher capacity Lipo's it will be even better as they will run smoother and cooler and alow longer run time!
Just my 2 cents!
No this boat is design for 26CC gas engine, some moded 26CC Zenoah engine can produce almost 5HP (3600W) and the very best are given for 6HP, that said you need to have some bigger motor to go fast, that's just my point of view but... two 580 under 6S would be certainly better, the bigger the hull is, the higher cell count you want to have in order not to pull very high amp! Take it this way... let's say you need 3000W to move that hull fast, under 4S that's 202A
(so 101A per motor as you have 2) under 6S that's "only" 135A total so 68A per motor, much more reasonnable isn't it?You could go for a pair of 540 10XL unders 6S but these motor are rated for 66A (not max but at their best efficiency) so there no room for playing, I personnaly try to use the Feigao at 80% of the max amp because this is the constant amp draw required but burst (at startup) it'll pull at least 80A! If you go for a pair of 8XL that are rated for 83A, because the KV is too high, you won't run 6S no way even with a 42mm prop (that's what I use on my 29" mono under 4S), and you can't reasonnably and efficiently pull 1500W out of a 540XL motor, you need to go for a bigger baby!... 580L!
Talking about Lipo's now, according to the above explaination, if you need 68A constant per motor and probably 90 or 100 burst on 6S pack, some 5000mAh 20C/30C can do it, 20C means they can supply 20x5000= 100A constant, 30C is the burst amp rating. but if you can go for higher capacity Lipo's it will be even better as they will run smoother and cooler and alow longer run time!
Just my 2 cents!
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