40s Johnson and Evinrude

[kevinrude]

I’ve been toying with the idea of getting a PO-15 and maybe an Evinrude SportFour.

So, other than the obvious stuff (e.g. compression, rust in tank, etc.), what specific things should I be looking out for in these motors?

For example, I know that with Speeditwins you have to check the flywheel as they had a tendency to throw them. Did the SportFour have a similar problem? Are there any parts of the PO-15 that are typically missing and/or hard to find?

Thanks. Just trying to know a little bit more before I go shopping!

[Mumbles]

I’m no expert on those motors but I did adopt a PO-15 a little while back. It had been sitting for years in a shed with no cap on the tank so the kids filled it half full with dirt so check to see what’s inside the tank! The tank didn’t rust because it’s aluminum but it did corrode thru a bit on the bottom and it took a while to get it shiny clean inside again. The gearcase had zero water in it with fresh clean grease. The coil didn’t check out right so that got replaced. The carb float was wrinkled up and separating so I made a new one out of two modern floats which I’ll post in the Members Only section later. The motor has good bounce and the pistons and cylinders look great and the missing tiller came with it but wasn’t attached so the only parts missing to make it complete would be the spark plug covers. Also check the thumbscrews as they tend to seize up over time.

PO 15 as found.

Starting to cleanup well.

Most important, everything inside looks good.

[jerry-ahrens]

It’s a good idea to check the flywheel torque on both models. I don’t think this is a design flaw particularly, but maybe just something that is overlooked. If memory serves, I believe 65 ft. lbs. is the correct flywheel nut torque on the PO. Both are great motors and easy to find parts for.

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[jerry-ahrens]

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[kevinrude]

Thanks for the information, guys.

A follow up question. What is the part the red arrow is pointing to? Water pump?

Thanks again.

[Mumbles]

It’s the idle relief valve. A little stainless cup inside slides up or down to open or close the valve. There’s no water pump to deal with on the PO’s as they have the pressure/vacuum system which relies on the prop and boat movement to force water thru the cooling system.

Nice motor Jerry! Hopefully mine will be looking that good some day!

[jerry-ahrens]

Thanks Mumbles. I bought that PO back in 1989,out of the trunk of a guys car in the Wal Mart parking lot. I was a tire and lube man in the Wal Mart auto center at the time! I sneaked out from work and bought the motor, since the owner had brought it all the way from Iowa to Missouri for me. Believe it or not, I restored it shortly there after and never tried to run it till a few years ago. I have three other PO15’s so I thought I would keep this one for show. The PO is really a fun motor to run… easy starting and plenty of power too.

[r-c]

The most lost or missing part is the spark plug covers. Two reasons they where taken off. First, easy access to the spark plug. Second, with the open wire terminal to the plug, it can and would short out to the plug cover. (You can cure this by spraying the inside of the cover with an insulation spray). Look around the garage, barn or where ever the engine is stored, on the walls for a nail in the side of the wall holding those covers.
For a PO, it could have been "hot rodded" on a small boat. Because they look like a racing model SR or PR, the local kid thinks he has a race motor and would over rev it. Simply rock the flywheel back and forth in all directions for play. More than say 0.004" it is lose and may need re-bushing as well as inspection of the rod and crank condition.
The Speeditwin for some reason didn’t get this abuse, but check the same way.
The Mercury KG-7’s lived the same type of abuse as the PO. It looked liked the engines raced at the time.

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