Old Johnson

[garry-in-michigan]

They needed that heavy oil to seal the rotary valve. Carbon buildup in the driveshaft housing was always a problem. Later models had sealing rings on the valve that are also used on later V-4, 6 & 8 models. The racing model had roller bearings on the connecting rod big ends and crankshaft mains. Also high compression two ring forged pistons and open exhaust. Several antique "A" racers made high compression pistons the convert the Army-Navy surplus Johnson 10 horse water pump (which had the roller bearings) into a class"A" racer. . .

[labrador-guy]

I think I have the center section cleaned out. Anybody want a start to make a diamond? Just need some pressure and a few thousand years and wha-la! Seriously I think Johnson had a engineering mistake when they built this center section. The center section on this KD15 is a aluminum casting with three tubes cast inside. Up water, down water and two exhaust. Must of been a bugger to cast. The voids are rough and there are casting slag that catches debris. Plugging is inevitable! Easy fix= exhaust cutout!
She’s on hold for a while, yard work!
Thanks to anyone that contributed to this tread!

dale

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[Tubs]

Today’s 2 cycle oil is so much
better than that of the past. Motors
exhaust could become so blocked
with carbon that they wouldn’t run
wide open. Only a small percent of
today’s oil burns. That’s why the
smoke is gone. That along with the
detergent they have today its put
an end to this PIA.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[bob-d]

Tubs and Mumbles, can you use " modern oil" (Pennzoil or Mercury) for these engines or only the Aeroshell 40?
Thanks

[Tubs]

Everyone has there preferences as to what
type and how much oil to run. I personally
use Pennzoil Synthetic in all my motors
starting with a 1920 Evinrude RBM.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[Mumbles]

I used off the shelf TCW III in my KA-37 and it seemed OK as the motor itself is in great condition internally. I did manage to pick up a liter of aviation oil while at the airport recently but I want to try it in a worn Light Four to see if it will improve the running characteristics over the TCW III oil. It will be getting used sparingly as it cost over $10 per liter!

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