MHZ Hunter brushless build

[5150WS6]

So most of the lakes close to me and easy to get to are not allowing 2 strokes let alone any gas motors on some of them. So midway through Im having to change to electric Hunter hull from an inline twin 70cc mated to a gearbox, then into the dual Merc drives.

Its a big boat. 69 inches roughly and 13lbs without any hardware.

I want a good balance between speed and run times.(duh who doesnt right?) I dont need 80mph but would like to be in the 50-60mph range.

Heres what Im looking at. Two of MHZ Scorpion 5035-760kv motors mated directly to the drives. I think the drives are up gear 7% ish? They also have a limit of 30,000rpm max.

For ESCs Ill do twin Swordfish X+ 300amp set ups as Ive run them in the past and they have been pretty decent.

For batteries. Local shop has Thunder Power Rampage series 7700mah 6s 70c lipos. I might do the 5s just because I worry about the drives holding up to a 12s set up and think 10s might be better. Drops it down to around 28k vs 32k with the 12s.

In the 5th scale cars I know its better to run higher voltage but not use all of it. Better run times, cooler stuff. Is this the same for the boats? The motors will be water cooled.

Just want some input on the set up. As I said. I don?t need catamaran speeds because I?ll never get them but Id like a 50mph boat that would run for 15 minutes? Not sure I can afford to get two sets of batteries at $360 a piece. 8 would be almost three grand and Im running out of kidneys to sell on eBay.
So Im trying to get the most bang for my buck initially here.

Thanks for any input and suggestions,
Mike

[vvviivvv]

I have a big MHZ mono, although a custom MHZ skater

Powered by twin Lehner 3040 700kv on 12s, runs around 80mph with 65mm props.

run time a lot shorter than you are desiring...

[5150WS6]

What mAh battery size are you running?

That?s a beautiful boat! So I?m guessing more 5-6 minute run times?

[Old School]

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I want a good balance between speed and run times.(duh who doesnt right?) I dont need 80mph but would like to be in the 50-60mph range.
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In the 5th scale cars I know its better to run higher voltage but not use all of it. Better run times, cooler stuff. Is this the same for the boats? The motors will be water cooled.

Just want some input on the set up. As I said. I don?t need catamaran speeds because I?ll never get them but Id like a 50mph boat that would run for 15 minutes? Not sure I can afford to get two sets of batteries at $360 a piece. 8 would be almost three grand and Im running out of kidneys to sell on eBay.
So Im trying to get the most bang for my buck initially here.

Thanks for any input and suggestions,
Mike

Big electric boats cost BIG money. As regards running your boat at lower power settings to extend runtime then be very careful as I believe that a marine ESC will fail prematurely if less than full power setting is used.

[fweasel]

Big electric boats cost BIG money. As regards running your boat at lower power settings to extend runtime then be very careful as I believe that a marine ESC will fail prematurely if less than full power setting is used.

They won't fail necessarily, they will run hotter because of the constant electrical switching going on inside to run at partial throttle levels.

[vvviivvv]

What mAh battery size are you running?

That?s a beautiful boat! So I?m guessing more 5-6 minute run times?

I haven't actually ran her yet - i bought her in January and have been offshore since, hoping to run her in December when im back on dry land...

I have a set of SLS Magnum v2 5000mah packs for use, I will experiment in the future with maybe a 2p setup and some smaller props for a longer run time.

I also have a 14s setup from my C5008 i could try but i believe it would be too much for this hull and don't want to damage the beautiful paint job.


I have plenty of info from the previous owner and also some videos but as a ball park - that's what to expect.

[Peter A]

Sorry but you will not get 50 mph for 15 mins without large capacity batteries, think 30,000 mah per motor.

[5150WS6]

Sorry but you will not get 50 mph for 15 mins without large capacity batteries, think 30,000 mah per motor.

Ok good to know. I will look at some larger mAh sized batteries. I know MaxAmps has some from 10k-20k. Maybe I can shoot for 10 minutes lol!

Big boats are expensive. Everything costs money to go fast.

And as far as running the boat at a lower power setting. The ESCs are rated from say 6s-12s. I meant running a higher voltage cell but change props to not make the batteries work as hard. Does that make sense?

Like in crawlers. Most guys run 2s but some of us run 3s. I can run almost twice as long using 3s and a lower mAh. That may not translate over to the boats though. Im still a newb on the big brushless boat set up. Part of why Im here is to get my learnin on! :)

[5150WS6]

Sorry but you will not get 50 mph for 15 mins without large capacity batteries, think 30,000 mah per motor.

And around what C rating should I be looking at. Thunder Power had 70c but the MaxAmps are 40c. Granted the MaxAmps are 16,000mAh and the Thunder Power are only 7700mAh.

I remember a electrical engineer buddy of mine said something about the more mAh the smaller C rating you could get away with??but it escapes my brain why or how.

[vvviivvv]

previous owner got 6-8 mins depending on what he was doing with my skater, using SLS 8000mah packs. 30k is way overkill imo (especially at 50mph)

[LibertyMKiii]

Ok good to know. I will look at some larger mAh sized batteries. I know MaxAmps has some from 10k-20k. Maybe I can shoot for 10 minutes lol!

Big boats are expensive. Everything costs money to go fast.

And as far as running the boat at a lower power setting. The ESCs are rated from say 6s-12s. I meant running a higher voltage cell but change props to not make the batteries work as hard. Does that make sense?

Like in crawlers. Most guys run 2s but some of us run 3s. I can run almost twice as long using 3s and a lower mAh. That may not translate over to the boats though. Im still a newb on the big brushless boat set up. Part of why Im here is to get my learnin on! :)

Max Amps are over priced junk. You would be better off buying 2 batteries and running them in parallel for the extra capacity.

[Peter A]

previous owner got 6-8 mins depending on what he was doing with my skater, using SLS 8000mah packs. 30k is way overkill imo (especially at 50mph)

Having set up and run electrics for endurance I know that if you want speed and runtime it takes many mah. I ran an Osprey on 12s, 65-70 kph and it took 20,000 mah to do 20 mins. You need a low average amp draw to do it. For that reason high C ratings are not necessary. I was running an average of around 50AH and using Turnigy 6s 20AH 10C Multistar packs.

The same motor/esc in a 45"mono, I have been able to get 8 mins out of 6000 mah at 60 kph.

[5150WS6]

Having set up and run electrics for endurance I know that if you want speed and runtime it takes many mah. I ran an Osprey on 12s, 65-70 kph and it took 20,000 mah to do 20 mins. You need a low average amp draw to do it. For that reason high C ratings are not necessary. I was running an average of around 50AH and using Turnigy 6s 20AH 10C Multistar packs.

The same motor/esc in a 45"mono, I have been able to get 8 mins out of 6000 mah at 60 kph.

Peter,
You pretty much just answered my next question. Thank you. That gives me a good idea of what I need. Just trying to find a happy medium between run time, speed and having to sell a kidney on Ebay to pay for it all!

So that helps. Thank you for the numbers and ideas.

Mike

[Peter A]

Motor is a TP 4070 440kv. prop on the osprey Prather 240 detounged a little. On the 45 I ran a 60mm Graupner carbon prop. I was just playing around.

[5150WS6]

Motor is a TP 4070 440kv. prop on the osprey Prather 240 detounged a little. On the 45 I ran a 60mm Graupner carbon prop. I was just playing around.

It really helps to have hull sizes, details and numbers and run times you?re getting. That?s been the biggest help so far. Kind of gives me real world data to at least shoot for or know what I?m getting into.

I?m going to try to get some decent size batteries as it is such a big hull. Also I have the geared drives so those will take some guts to make go also.

Thanks for the details! Appreciate it for sure!

Mike

[vvviivvv]

For reference, my modified skater above is 1.67m so around 66"