Battery

[dellquay13]

Hi Paul,

All electric start outboards have an alternator built in to charge the starting battery, usually about 20a max, and some manual start outboards have smaller rated ones to run nav lights etc. I'm pretty sure your yamaha has an alternator. I had a 1999 40hp 2str Yamaha electric start and that had a decent sized alternator.
I use a Numax marine battery for my electronics and nav lights, and a Bosch car battery for cranking, with a voltage sensing relay for split charging and have never had battery problems since buying reputable brands. I don't want to take risks with battery failures when spending up to 3 days at a time out at sea.

Chris

[Adam]

Hey Paul, my battery is 2 years old and I consider to buy another, the same, one in the case that the main one fails being on a couple of days trip (same as Chris said).
You can go for car battery if you want to save some penies, that's not a problem but they are build a bit different to the marine ones.

[DACS]

The engine if it's electric start will still charge the battery.

No necessarily. I had a Johnson 20hp 2-stroke with electric start and the only electrical output was 12v AC for navigation lights. A previous owner had fitted a rectifier but 12v DC would not charge the battery as I discovered the hard way. Fortunately the engine also had a recoil starter.

[535Mustard]

I expect that's because the electric start was not original and standard from new. It was added by a previous owner would be my guess.