Facts about Evinrude/Johnson racing outboards made my OMC

Attachment 470703

Never seen the flat exhaust on a F-1 V-8.

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Originally Posted by lars strom

Another F1-V8 engine is getting service at the races by OMC.
There was two cylinder head castings. This is the one without detached cooling plate. Also the first “flat type” exhaust manifold.
So much fun thinking back on those powerful 2 stroke racing V8 engines.

Attachment 470637

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Originally Posted by Instigator

Never seen the flat exhaust on a F-1 V-8.

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Well..the OMC F1-V8 powerhead used the "flat" exhaust manifold from the start 1981 to the end of 1983. I did send my 1983 engine to Waukegan , Illinois after the season and got it updated to the newer more rounded exhaust manifold. Got a bit more speed after the update.
Here is a few more carb powerhead with the flat manifold.
Again, thanks for clicking in here.

https://www.screamandfly.com/attachm...2&d=1541354871
https://www.screamandfly.com/attachm...3&d=1596244911
https://www.screamandfly.com/attachm...4&d=1527762241

Thanks John Tiger & Laura Tiger for your support and enjoy the new classic race t-shirts.

Attachment 470735

Lars, I can see why you got more speed with the rounded exhaust.
The flat exhaust, looks to be more restrictive in exhaust flow.

https://www.screamandfly.com/attachm...5&d=1596119247
https://www.screamandfly.com/attachm...7&d=1596135779

Kinda like the bubble back exhaust on the old 135 V-4 cross flows compared to the lower horse flat backs.

It is impressive to me to see this history and the effort and expense that they/OMC were willing to put into the R/D of that motor.
We all know Merc did too but those all started as fish motors and were modified from there.

This started as a blank chalk board w/a bunch of engineers and tuners staring at it....
Gotta love that.

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Originally Posted by Lake X Kid

Lars, I can see why you got more speed with the rounded exhaust.
The flat exhaust, looks to be more restrictive in exhaust flow.

https://www.screamandfly.com/attachm...5&d=1596119247
https://www.screamandfly.com/attachm...7&d=1596135779

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David Blanchard

I bet no one has a set of the engineering assembly specs anymore

Attachment 470763

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Originally Posted by Instigator

Never seen the flat exhaust on a F-1 V-8.

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it was the first version with rectangular exhaust cast into the block and light rods
Then they changed the casting to oval style and changed exhaust cover and somewhere in all that changed to the heavy rods so rpm was no longer a problem.
So there are 3 exhaust styles as it changed again, then added CFI then went 3.0.
I have never seen anyone list all these changes out and the order they were changed.

Attachment 470764

Saved!

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Originally Posted by lars strom

David Blanchard

I bet no one has a set of the engineering assembly specs anymore

Attachment 470763

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Thank you sir!

I don’t remember the rod change either.

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Originally Posted by powerabout

it was the first version with rectangular exhaust cast into the block and light rods
Then they changed the casting to oval style and changed exhaust cover and somewhere in all that changed to the heavy rods so rpm was no longer a problem.
So there are 3 exhaust styles as it changed again, then added CFI then went 3.0.
I have never seen anyone list all these changes out and the order they were changed.

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Back out on the water..

Attachment 470768

Looks like 4 "Y" , two into one , spaced 180° in "Y". Four twin cyl stackers dumping down into the mid.
(1-3),(2-4) and (5-7),(6-8) in that "bubble" , who has a pic?

Attachment 470769

The 1985 model.
The very sexy 6 inch midsection and fuel injection

Attachment 470773