Evinrude 70Hp Mysteryhole?!

[solidswede]

I really REALLY need help on this one...Just managed to tear down the !exhaustplates" on my engine. It?s a 1975 70 Hp Evinrude. On the top hand corner of the block/head (see image) i found a hole. Is it supposed to be there? Does anyone know how big it was when it came from the factory, or even have a picture to compare with?
I really want to know so please answer and save me from sleepless nights I know that cooling water has to come from somewhere but it seems to be such a tiny hole Best regards Thomas

 

[Daviet]

Re: Evinrude 70Hp Mysteryhole?!

I think that you are looking at a vent hole to let the air out as the housing fills with water, otherwise the air would be trapped there and cause hotspots.
I am sure others will come along and add to this post.

 

[solidswede]

Re: Evinrude 70Hp Mysteryhole?!

Thank You for fast reply Daviet, i like your theory.

 

[jtexas]

Re: Evinrude 70Hp Mysteryhole?!

ok, this is the answer to a mystery that's been nagging me for years.

There's a 1994 service bulletin (see below) for relocating the telltale outlet to the top of the cylinder block to vent any trapped air from the system, but it only applies to 1986 through 1994 3-cyl motors.

I've been wondering why they didn't recommend it for older models..........

 

[solidswede]

Re: Evinrude 70Hp Mysteryhole?!

Wow i am truly amazed at the speed You Guys can find all these facts. I guess that this gives more proof that Daviet may be correct . Thank?s jtexas for this great piece of the puzzle and glad to have helped to lay an old mystery to rest.