Reply To: Powerhead to lower unit gasket, 5.5 Johnson

[Dale]

Terrel Beckham wrote:

Antique Outboard Friends,

As an addendum to this project, I was curious about the water circulation pattern on these engines.  The bulk of the cooling water enters on the throttle side, circulates through the power head and exits on the shifter side.  I did notice a small, machined passage, shown on the attached photo.  This would allow a small amount of the return water to exit into what I’ll call “shaft alley”.

Can anyone tell me the purpose of this feature, as it applies to the water circulation scheme?  I’m continuously impressed by the smart design features of these ’50’s vintage engineers in their products.  Slide rule guys knew their craft.

I too like to follow those drillings  and the cavities to see where they go and why they do what they do!  Some engineer found out an outboard is a lot quieter with the exhaust going out under water.   Another engineer found out that a small exhaust relief port keeps the motor running at low speeds.  Another dude sent some water down the exhaust to cool it and the water came out the exhaust relief so we know the darn thing is cooling itself..  Only took about 50 years to get that far!   One thing for sure they didn’t tell us everything we have to learn it for our-self.  I have found water tubes with holes drilled in them.  Some outboards get black from heat just under the power head, maybe a mechanic did his own engineering.   It sure is fun trying to figure stuff out on these old timers!

dale