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Old 29 January 2013, 11:48   #1
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Country: UK - England
Town: macclessfield
Boat name: Reach Out
Make: Quicksilver
Length: 4m +
Engine: 30hp Tohatsu EFI
Join Date: Aug 2010
Posts: 301
Small SLA battery, not the 100Ah 22kg...

On a small boat with 30hp, the 22kg battery mounted under the vented bench seat towards the rear of the rib along with the upto 22kg of fuel and 90kg of me can not be ideal.

I was wondering if a replace the monster battery (which is in perfect condition) for a much lighter one may help performance.

I have corrected the propeller height by converting to long shaft, fitted a shorted pitch prop in stainless steel... now 12 inch rather than 13 inch. so I am hoping this is sufficient to get on plane ok ... quicksilver ocean runner 410.... 30hp tohatsu efi all 2010, with pull start and electric start.....
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Old 29 January 2013, 12:14   #2
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
FWIW I have been running my 60Hp with a built in VHF on a 60Ah bog standard car battery for the last 5 years. (it was as a result of the original battery that came with the boat keeling over mid me being a rescue boat at a week long event, and was all the local Kwik fit had to hand that would fit in the console). It has since died by toasting, as I hadn't realised the Merc Clamshell rectifier is just that, so it had seen the best part of 50+ hours being "toasted" at upwards of 19V! I have since replaced the rectifier with a regulated one off a honda.

The toasting reduced it to the capacity of a couple of AAs, so I replaced it. Got a deal on an 80AH leisure batt, as I now have a plotter to feed as well..... F*ing ell it's heavy, especially compared to the same sized one that came out!!

Some on here would probably reckon 80Ah isn't enough, but I have a Bulgin Buccaneer on the side of the console - it sits at home on a trickle charge, and gets a top- up from the car's "caravan" socket en route to the slip.

Once your engine has started, (and being a 30HP you can probably pull start it pretty easily) then it's doing next to nothing. Even if it doesn't have the guts to crank, you can walk to the transom & pull.

If kept well, a small car or big motorbike battery should do the trick nicely, even if you accidentally abuse it for 5 years!
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Old 29 January 2013, 16:44   #3
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Country: UK - England
Town: macclessfield
Boat name: Reach Out
Make: Quicksilver
Length: 4m +
Engine: 30hp Tohatsu EFI
Join Date: Aug 2010
Posts: 301
It's the weight that concerns me, as the boat did not perform well before I altered it, and now I hope it works as it should. Is the 22kg worth the hassle to get it to 5 or 10 kg...?
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Old 29 January 2013, 16:47   #4
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Country: UK - England
Town: Dorset & Hants
Boat name: Streaker/Orange
Make: Avon/Ribcraft
Length: 4m +
Engine: 50Yam/25 Mariner
Join Date: Apr 2007
Posts: 5,551
Quote:
Originally Posted by simsy View Post
It's the weight that concerns me, as the boat did not perform well before I altered it, and now I hope it works as it should. Is the 22kg worth the hassle to get it to 5 or 10 kg...?
Yep ..30hp...most fun I I've had in a RIB
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Old 30 January 2013, 08:54   #5
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
FWIW, my old SR4 had a 25 on the back when I bought it. Could make 21 knots (just) with 30L fuel, me (about the same weight as you) and a mostrously heavy home built jockey.

I upped the gee gees to 30, and got it up to 23 knots. If these are the sort of speeds you are getting, you might be at or around the limit of the engine.

I had a 13" prop - it wasn't fast onto the plane, but was OK when it finally got there. Never had a tacho on it, so can't tell if it was maxing out on revs or not.


Put it in prespective - 22KG is a bit less than a tank of fuel. Do you get a spectacular difference when it's empty compared to fully fuelled? - Moving the weight around might be the way to go.
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Old 30 January 2013, 14:13   #6
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Country: USA
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I used to run a Honda 40 off a garden tractor battery (about the size of a large motorcycle battery.) Weighed about 15 lbs; used it for starting and also powering a handheld GPS. If you have more load, you may want more battery.

jky
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Old 30 January 2013, 17:46   #7
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Country: UK - England
Town: macclessfield
Boat name: Reach Out
Make: Quicksilver
Length: 4m +
Engine: 30hp Tohatsu EFI
Join Date: Aug 2010
Posts: 301
I have only used the boat for 30 minutes with the prop way too high, so I have no feel for performance as yet...
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