1979 35hp Johnson - smallest battery?

[Hetek]

Was wondering if I could use a motorcycle battery for my electric start 1979 35 hp (35e79a). Or do I have to use the standard marine group 24 size? No heavy loads - just running lights. Weight and physical size are my main considerations. It’s only a 12’ boat.

Motor is new to me. Owners manual is in the mail.

 

[Crosbyman]

lots of variables here...
current draw needs of the starter
how good does the engine start
does it start good with the spare pull cord in case that smaller battery goes RIP
to big is better than to small ....
bring a set of oars and PFD ... a 35hp on a 12 footer and you :-(

check and do not exceed HP rating in case insurance won't cover you for liabilities

 

[909]

By far, the lightest and most powerful batteries would be lithium.

Instead of purchasing an expensive lithium ion battery , you can make one.

The box is roughly the size of 3-4 water bottles.

It weighs ~ 10 LBS

I use cells that would have gone in the landfill.

I wrap the cells in PVC electrical tape. The box is sealed.

I managed to fit 76 cells in this box, which yields approx 40 Amp Hours .

This weekend I trolled for 6 hours and came home with over 60% battery life remaining.

Other uses include outboards with electric start like yours , charging cell phones , fish finders, running lights, speakers , trolling motors ..... ect

The shaft is cut extra short & weighs 20 lbs total .

 

[racerone]

Garden tractor battery will do the trick.-----Motor in good condition will start in just seconds.

 

[tphoyt]

Do you have a custom made transom on the 12’ boat? Sounds like trouble to me.

 

[Hetek]

All good points. I can add…

Boat is a Glen-L “TNT”. I had a 1978 Evinrude 35 (manual start, short shaft) on it before. I’m putting it back together now as a father/son project but this time it’s electric start, hence the battery question.

With the 35 it was very quick but not crazy. I know of a few others that were powered as high as 55hp. Now THAT is crazy! I did build it with a beefier transom than spec.

Motor starts on the third pull using the rope around the flywheel when cold.

Here’s a pic. The Trans Am decal on the deck makes it go faster.

 

[jimmbo]

I hope that Beefier Transom is attached more Beefierly to the rest of the Hull

 

[tphoyt]

Looks like lots of fun.
It reminds me of my 79 Trans-am.
I know that’s was lots of fun
Glen-L makes great plans.
Enjoy the ride.

 

[Hetek]

Gotta say thanks to racerone. He hit the nail on the head. I did a little research and found a marine group U-1 battery which is basically half of a group 24. Very similar to a lawn tractor battery. They even make marine battery boxes with hold-downs for it.

My original thought was why do I need the same battery that I had for my V6 175hp Johnson (on an 18’ Baja) for a simple 2 cylinder 35 hp? Pretty sure the answer is, I don’t.

And guys… Please don’t fret about my transom. The Glen—L plans didn’t have the compartment behind the seat you see in the picture. It was wide open with less support. The transom is now tied into the deck and the coaming, and there is a double transom knee to the keel. All built with marine plywood, Honduras mahogany and Sitka spruce, fastened with epoxy, bronze screws and annular ring nails and a full skin of fiberglass. I built it the beefiest of beefier beefus beef. It handles a 35hp fine.

Just don’t ask about my 14’ Checkmate with a Johnson Stinger 75 hp, 15” short shaft… That one was a handful!

 

[tphoyt]

I once took a ride in a 19’ modified Glen -L design with a 235 on it. We topped out at 104 in the off shore grand pre amateur division and brought home 1st place. It was like riding on a pice of cardboard with a motor on it.
Good times.