Starting battery for a 1991 Avon S3.45?

SBH2OMan · 01 April 2010, 01:14

Hello all,

I'm really struggling a bit with this one, and would love some advice. I recently acquired an older S3.45 (the one with the center seating console and front cowl-mounted controls). It has an Evinrude 2-stroke electric start 30 which starts on the first pull, but the boat came with a tiny motorcycle type battery that is completely dead and won't take a charge.

I ran out and bought a spiffy new Group 24 marine battery and box, and brought it home only to find that it wouldn't fit under the rear-facing seat! (too tall).

Does anyone know what the original battery setup was for this boat?

I'm thinking that a U1 size battery would fit, but IIRC, they are usually "wheelchair" batteries designed more for deep cycle applications than for starting oomph....

I'm grateful for suggestions - The motor has a 4-amp charging circuit and I'd love to be able to just start the motor and be able to run a Fish Finder/GPS unit and perhaps a 12v receptacle for charging a hand held VHF radio while underway.

Thanks in advance,

-Brent

9D280 · 01 April 2010, 11:31

I'm going to be controversiol again. If your 'rude is a 2- stroke 30, I suspect you could start it with a motorbike batt, and not worry about flattening it in the process. Fishfinder isn't going to pull much more than the lights on a bike (that by law need to be permanently lit!) so I'd say you'll have plenty of capaciy in a small bike batt.

Worst case, you have a buit of string to pull to make it go - the alternator will keep the fishfinder going when it's running, even if the batt is so flat it can't turn the starter.

SBH2OMan · 01 April 2010, 14:40

Controversial? (safety of having a "marginal" battery?)

Encouraging suggestion, nonetheless, as a motorcycle battery (or one for a PWC) will be much less costly than a typical marine battery.

The fellow at West Marine suggested that I need a minimum of 300 MCA, which I don't think can be found in a motorcycle battery.

I'm thinking this one looks like it might be a good one, and appears that it would fit inside a "U1" sized marine battery box:
http://www.amazon.com/Odyssey-PC625-...0130058&sr=1-3

9D280 · 01 April 2010, 15:29

Yeah, in a nutshell!

I currently have the smallest, cheapest battery I could lay my hands on in a hurry (in a hurry being the key point!) . It runs a Garmin GPS and a VHF, not to mention 35-ish W of Nav lights. Only when I was out tweaking and testing and cranking the engine every 2 mins for an hour did it start to loose the will to turn. On paper, I should be using the pull chord all the time, but taking a slight reality check:

- 2- strokes are self supporting, the battery is literaly only there to turn the starter (and energise the choke solenoid!), after it fires, it's 100% on charge, and it's only cranking 2 or 3 small cyls.

- once running, an outboard will be running at reasonably high RPM for a good chunk of the time (i.e oodles of recharging available)

- You'd be surprised how much of the power to run your toys actually comes direct form the alternator.

Bottom line is, what's the worst that can happen? - you have to go to the back & pull a bit of string! Once going, the engine will keep your toys alive. The advantage of older engines is they don't need external power to keep running, unlike a lot of modern cars are stuffed if the battery dies.

I should add that you will still need a battery (even a mostly gubbed one) to flatten out the nasty electrical spikes you get from the alternator, otherwise you risk frying your electronics.

jyasaki · 01 April 2010, 16:37

Used to run a 14' Achilles with a Honda 40 4-stroke; the battery used was a Orchard Supply sourced Lawn and Garden tractor battery. The last time I replaced it, it was something like $35. Worked fine for starting and running a couple of handheld electronics.

jky

SBH2OMan · 22 April 2010, 20:58

Excellent! Thanks for all the help.
(Dang, I with email notification was working for thread subscriptions!)

I will be installing the FF/GPS and VHF next weekend with the existing motorcycle battery, so we'll see how it goes. I've run the same GPS/FF combo from a back of 8 AA NiMH batteries all day long in a kayak, so I know the current drain is very very minimal.