Have a 68in fiberglass hydro hull. Want to make it electric. So I understand that boat size and weight are 2 start points. Do I weigh the empty hull or am I supposed to guess the weight of hull with prop, prop shaft, motor batteries ect?
Junior Member
Getting started. Help Me!
Have a 68in fiberglass hydro hull. Want to make it electric. So I understand that boat size and weight are 2 start points. Do I weigh the empty hull or am I supposed to guess the weight of hull with prop, prop shaft, motor batteries ect?
Senior Member
What are the plans for the boat?
How fast do you want it to go?
Do you have a certain battery cell count in mind?
Junior Member
JustOriginally Posted by LibertyMKiii
Junior Member
Just want to finish something and enjoy it. Don't understand all the technical stuff like how many battery cells are best and why. So "If" it is realistically possible. 50 to 70mph and 8 to 10 minutes of run time would be great.
Senior Member
To have a decent run time on a boat this large you will want higher voltage. (more cells)
The reasoning is that it requires X number of watts to make the boat move 50 mph.
Watts are made by voltage * Amperage. Pulling amperage will shorten the run time so you want to compensate by having higher voltage.
I would say you want a high voltage ESC and lower kv motor, but I dont have experience with a boat this big.
Junior Member
Thank you. That is a start to what I need. Explanations to help me to make decisions.
What about rims? I mean in SST-45 tunnelboats the boat was 13ft and fully rigged, driver and fuel, minimum weight was 675 pounds. And they were running 75 to high 80's. But of course the props were like 7 1/2 to 8 1/2in diameter but motor was turning about 7600rpm
So a boat this big could I maybe get a lower rpm motor and custom prop to offset and get the speed. Or am I showing my stupidity?
Senior Member
On the main page of the offshore electrics site you will find the speed calculator.
You plug in a motor KV, cell count, and then the prop pitch and diameter. It would recommend shooting for a speed of 50-60 mph on this boat due to its size.
You can look at prop sizes on the store's propeller section. Id imagine you want one of their largest around 65mm diameter minimum.
The down side to a larger prop is more drag and requires more power to turn it. I don't see this one being able to run for more than 2 mins tops.
A gas motor may be the only option if you are looking for that 8-10 min range.
Junior Member
[QUOTE=LibertyMKiii;772728]On the main page of the offshore electrics site you will find the speed calculator.
You plug in a motor KV, cell count, and then the prop pitch and diameter. It would recommend shooting for a speed of 50-60 mph on this boat due to its size.
You can look at prop sizes on the store's propeller section. Id imagine you want one of their largest around 65mm diameter minimum.
The down side to a larger prop is more drag and requires more power to turn it. I don't see this one being able to run for more than 2 mins tops.
A gas motor may be the only option if you are looking for that 8-10 min range.[/QUOTE
Again, Thank you very much. I will process everything you have been teaching me. And I will be back. Thanks]
Senior Member
How about a picture of the Hydro?
Junior Member
New here and don't know how to add a pic.
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