This is a very tough thread to address. I don't want to discourage the OP but it seems his expectations are not realistic, particularly in cost. I'll give a few ideas and will be happy to follow up to questions.

First order of business: READ: http://www.rcuniverse.com/forum/m_9069147/tm.htm

Second: a 50" boat is not a good choice for a first electric boat. You should start with something smaller and learn how to rig and run an FE boat. Really. Seriously. But if you insist...

Third: a budget of $150 is totally unrealistic, even for a "slow" boat that size. Do you have the transmitter and receiver already?

Fourth: you need to decide what you want from the boat. You say 20-30 mph - but how long do you want the boat to run between charges? How long are you willing to wait while the packs recharge? Will you be running with other boaters?

I have built plenty of large FE boats, but nothing that "slow". To keep costs down an inexpensive motor on relatively low voltage (6S) may work, but the hull will have to go fast enough to plane or it will fail to work well. That means a propeller of at least 55 mm diameter. An x455 prop needs to spin around 15,000 rpm for 25-30 mph in a big mono. On 6S that means a motor with a Kv of ~700 with a minimum diameter of 40mm. A 180 amp ESC should be plenty. A 6S pack with a minimum of 5000 mAh and 45C would work - but two of them in parallel would give better run times.

I am handicapped by not knowing much about large boats running this speed, mine all go over 60 mph. Perhaps others can chime in. But regardless we are talking several times the $150 estimate, unless the OP can get his parts used - and it is highly likely he can. Even then $350 is low and that is excluding a charger and a radio.


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