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Author Topic: MFA Spearfish battery advice please.  (Read 2060 times)

exvtop

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MFA Spearfish battery advice please.
« on: August 16, 2009, 10:06:01 PM »

Just about to start an eBay purchased MFA Spearfish - 36x11ins offshore powerboat.
Planing hull I think.
Going to use an MFA 850 motor.
MFA recommend using a 12v 7Ah lead acid battery.
Having 5lbs of battery in a boat like this just doesn't seem right to me.
Thinking of using a 12v 3700mAh NiMH pack - weight 1Żlbs.
Apart from reduced duration (and increased cost) would this be OK or would I still end up having to add ballast?

Thanks.
Mike
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Shipmate60

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Re: MFA Spearfish battery advice please.
« Reply #1 on: August 16, 2009, 10:09:51 PM »

That battery should be fine.
I wouldn't add any additional ballast as this model is very stable.

Bob
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andyn

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Re: MFA Spearfish battery advice please.
« Reply #2 on: August 16, 2009, 10:13:48 PM »

Ditch the 850. Get on to Mark's Model Bits and order his 900 motor. With those 3700 nims it'll last about half an hour. See the traders section for pics of a 49" Perkasa with one in. Planes at half throttle.

You will not need ballast, weight is the enemy.
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exvtop

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Re: MFA Spearfish battery advice please.
« Reply #3 on: August 16, 2009, 10:24:55 PM »

Thanks for replies.
Will give Mark a ring.
Now I think about it I seem to recall a few negative comments concerning the 850 motor.
A bit of a current hog and not delivering the power you might expect.

Mike
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andyn

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Re: MFA Spearfish battery advice please.
« Reply #4 on: August 16, 2009, 10:28:06 PM »

Now I think about it I seem to recall a few negative comments concerning the 850 motor.
A bit of a current hog and not delivering the power you might expect.

Then I don't need to give the reasons why to ditch it ;) Try it on ebay if you have it already, then you can get a bit of money towards Mark's motor O0

There was loads of Mark's 900 powered boats flying around this weekend at the Mayhem do in Llanberis. They're getting very popular because they're very good motors.
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exvtop

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Re: MFA Spearfish battery advice please.
« Reply #5 on: October 09, 2009, 05:49:04 PM »

Just to add.
The boat is now running very well with an MMB 900 motor on 15 NiMh 3700 Ah cells.
Still going strong after 15 minutes.
Well pleased.

Mike
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martno1fan

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Re: MFA Spearfish battery advice please.
« Reply #6 on: October 09, 2009, 05:53:22 PM »

Hi Mike how about some pics and maybe a video of her running  :-)).
Mart
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exvtop

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Re: MFA Spearfish battery advice please.
« Reply #7 on: October 09, 2009, 06:02:56 PM »

Hi Mike how about some pics and maybe a video of her running  :-)).
Mart

OK, but I won't get back to the lake for another three weeks.
Video would probably be jerky stuff from my elderly stills camera :-)
Mike
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