Johnson PO-15 Prop Size?

[Buccaneer]

Are there props, Johnson, Evinrude, or other, that will fit,
or can be made to fit on a Johnson PO-15?
If so, what models would they be on? It appears
from photos that I’m looking for a 3 blade prop.

I measured the prop shaft at .892, but now wonder if
I read the caliper wrong. That doesn’t seem like a normal
size, nor could I find any prop data that had a similar bore.

Also, does anyone know the diameter and pitch of a PO-15 prop?

Thanks!

Prepare to be boarded!

[david-bartlett]

Buc,

No answer from me, but you might contact the PO Special interest group leader, Bill Salisbury. His contact info is in The Antique Outboarder.

I found a part #375581. A search on eBay brings up 2 props to look at, but no definitive info on size.

[outbdnut2]

I’ve got a PO-15 and the prop looks like it would interchange with the 15, 18, and 20 HP props that have the shear pin underneath from the mid 1950s and 1960s models but I’m not sure – Hmmmm……. now you got me wondering – I may have to pull the prop on my PO-15 and compare….oh darn, I can’t get to it until spring, I just put away my pontoon and a couple other boats and the PO is inaccessible behind them.
Dave

[Mumbles]

Your original 29-175 prop measured 12 X 13 but but Michigan supplied them in 10, 12, 15 and some other pitches. I think 29-39 was the original P/N for a 12 X 12 but I might be wrong. The last known good number for the 12 X 13 prop is 375581 and no, a prop from an 18 or 20 won’t fit as the PO has a much larger diameter shaft and drive pin. I’m pretty sure props from the other PO family of motors (Sea Horse 24) will fit though.

Here’s a snip from the ’42 Michigan catalogue. Check out those prices when an aluminum prop from your friendly Johnson dealer was around $5.25 back then!

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[Buccaneer]

Thanks for the replies gentlemen!
You gave me some fodder to eat my
way through.

How much would the prop diameter and pitch effect
the "forced" cooling on this engine?

Dave, you need a bigger garage, lol.
Mumbles, we need a time machine to "go back"
and buy some props!

Prepare to be boarded!

[george-emmanuel]

Buccaneer,

Your last response is the one that poses a concern over a good question! The PO depends on diameter for good "push" of the water through the cooling pickup on the gearcase—-especially if you are going to do some idling for any length of time. But if all you are going to do is run faster than an idle it becomes less important. I had a 12 x 12 on my Lyman and it did just OK and I couldn’t get full rpm out of the engine. I found a 12 x 11 and that lit it up. I have a 10" diameter prop that goes great on my aluminum boat but I can’t bring it down to a dead idle and get the cooling I want.

Normal test should include using a tach to make sure you are getting full RPMs.

There are Michigan AM props out there that give good performance also.

George

[outbdnut2]

quote Buccaneer:

Dave, you need a bigger garage, lol.

A bigger garage is a short term fix! There’s an age old rule for collectors that: "stuff expands to fill and overfill existing space and any added space!" [LOL!]

I added a 4 garage-stall pole barn 11 years ago, bringing my total to 10 garage stalls, and a double boathouse, but also 9 licensed watercraft plus a couple that aren’t and a couple old "project" cars……and with word out that I’m into the hobby, old motors just keep finding their way here…..but that’s a good problem to have! What I need to do is spend less time fixing motors for friends and more time on the hobby!…but I like helping friends out too!….and I take no pay but most give me beer!
Dave

[stanley]

My PO prop is stamped 375581 and 10 3/8 x 12 1/2

[Buccaneer]

Stanley, I presumes your PO runs out okay and
has adequate cooling water flow with that prop?

If my original prop was 12 x 13, how would
Stanley’s 10-3/8" x 12-1/2" affect performance?
Higher RPM’s, less speed ?

I am "Prop Illiterate"!
Thanks!

Prepare to be boarded!

[stanley]

Yes it does.I did have problems but with help from members on this forum they have been solved.I was having fuel problems which meant lots of stops and starts so the water never got flowing.The fuel issues also resulted in a lean condition and running with spark advanced to far which contributed to the problem.If the motor gets to hot before the water gets flowing you get a steam bubble and a blockage.Finally I measured the transom on my old wood boat.It measured 16".I cleaned the carb again cut my transom down to 15" and all is well.

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