I have a 1969 20 hp Johnson outboard. How do I know what pitch to get on my next propeller? I have no idea.

Also when I am storing my boat for winter, should I charge my deep cycle battery or leave it low?

Ok, pitch is how far forward the boat goes for a turn of the prop. I would say if the motor pushes the boat fine, dont change the pitch.. You'll can a few more mph, or loose a few, the motor can spin higher. It is a trial and error deal, trying out bigger and smaller props, and it will cost you $.

And to avoid a big explanation just keep the battery fully charged when not using it.

I can't help you with the prop, but yes charge the battery and you should be charging it as soon as you get back from every outing

NEVER EVER leave a battery down.  Perfect way to ruin it.  We have a couple spare batteries, along with our boat batteries, in our shop.  I run the meter over each of the batteries about once every 2 weeks, and if they drop to below 12.66 volts, I throw them on the charger for a couple hours.

As far as the prop, there is no way to determine what pitch you need, without a tach.  I doubt you wanna plunk down the dollars to put a tach on that johnny.  Great motor by the way.

Most props have a part number as well as size and pitch stamped near the hub.  Seing as it's a  1969 20 Hp thats pretty close to todays 15 HP as those were rated at the motor where todays are at the prop.

I would look at what most 15 HP or  20's are using today I bet  around a 9-10.5" Diameter but around a 10-11 pitch tops.

You didn't say what size boat, but they only make about five props for that motor anyway.  14' jon I would look at an 11.   If your going to be pushing much weight, then maybe a 10.  Back in the 60's/70's  they were running the 25 Johnson's on the San Antonio river walk barges they were running 9's on those with 30 to 40 people in them so that gives you an idea of what a 9" can do.  I ran an 11 on a 18 Evinrude on 250 pound 14' Fishmaster fiberglass fishing boat and it would run 26 mph.

You didn't say what size boat, but they only make about five props for that motor anyway. 14' jon I would look at an 11. If your going to be pushing much weight, then maybe a 10. Back in the 60's/70's they were running the 25 Johnson's on the San Antonio river walk barges they were running 9's on those with 30 to 40 people in them so that gives you an idea of what a 9" can do. I ran an 11 on a 18 Evinrude on 250 pound 14' Fishmaster fiberglass fishing boat and it would run 26 mph.

My boat is a 16 foot aluminum so I am not pushing much weight at all except for passengers and the deck I built in the front. And the problem is the original prop got lost and the one I had on it I took from an old motor my grandpa had. So I don't know what was originally on it. That's where my confusion has come from.

Thanks for the info guys. I'll charge the battery and go with a 9" with a 11" pitch.

Logger

Here was the only reference that i found on teh web that listeda prop size for the 20HP Johnson 1969

http://www.dixiemarinesales.com/Propref.aspx

20Hp (1969-1977)

389390 SST Propeller 9 1/4 x 9

763587 Aluminum Prop 9 x 9

763583 Aluminum Prop 9 x 10

389320 SST Propeller 9 1/4 X 12