"Name That Outboard"

[Sam La Banco]

The motor was a skunks works project, no class was in mind when Dave did it.
There were a few gear heads around there, he was one of the best.

The small carb was an OMC part. Not sure about the 2 Barrel.

[Sam La Banco]

Here is a look at the block and a shot of the engine on the boat.

I was in a 20 boat we borrowed from Wayne Walters, if you can see my hand on the throttle, I don't even have it fully closed, and the boat wants to lift off.

[calvin]

Wow..looks like a potent mill you got there you guys upnorth come up with all the good stuff..Remember the party a Foote Oberrys..I still have the paper plate you were using to jot down..the secrects of the 20h...Buddy

[Tim Kurcz]

Excellent stuff Sam!

The carb location and function make perfect sense now. It's neat the architecture worked so nicely. This is a very forward-thinking addition to what is basically a pontoon boat engine. The results are evident in the boat photo: You're lucky you didn't blow over! Thanks for posting your personal pix and divulging its secrets.

Tim

[Sam La Banco]

I remember the party, the rock fish, and the beer, but don't remember the 20H info on the paper plate, hope I didn't mention the crankcase align bore jobs we did, that was suppose to be top secret.

Dave's motor made quite an impression at a race in Wis. when we just set it on my boat or Paul Pittmans to see what would happen, it was almost a riot.

I will talk him into posting a picture of the 25 motor John was talking about.
maybe the riot picture too.

[calvin]

Yes the rock fish and BEER..remember talking to John Hervat..great guy ...hows he doin...are ya still racing sst 60..Buddy

[Tim Kurcz]

OK BRF engine builders, with the help of Sam’s block photo, I think I've got most of the radical OMC figured out. Can any of you explain how the side carb system works?

Tim

[Sam La Banco]

Tim, even though, now that you know the side carb is piston ported, it still has a few tricky details you can't see.

Also, we found that on dyno, spacing the intake manifold off the c'case a 1/4" was worth 1 hp on the old 22 cu.in. motor, this is the 33 cu.in. motor. I'm not sure with it's larger reed openings if it was needed. So, I'm not sure why Dave did it to this one, I'll ask, never saw what the reed set up is like, I just know it worked.

If you are interested, there is criteria for setting up a folded pipe in a midsection. I got the information from Dave and will try to find it if you are interested.

[bobvdinghyracer]

after looking at the ports a while looks like transfers opened to be 2 large ports instead of 4 .... BUT from what little can be seen apears to also be blocked off in middle of each , which makes sense due to added piston port hole below it and must be blocked off below also i assume with expoxy ..which looks like it also feeds the center of the now 2 transfers . then looks like the outer ends are fed from the case itself giving the appearance of a looper setup .... soooooo it either became a looper , or a real radical deflector . would luv to see the pistons and other side of the cylinder .. ie the exhaust side , and YES please show us the " folded ex sys. info " much interested !!
thanks
ps ... so which is it ??
or am i wrong on both counts ????

[Tim Kurcz]

Hey Sam,

It's interesting this engine liked an increase in CC volume (spaced forward carb/manifold), but whatever works!

Bob does an excellent job in analysis, but let me add on. The piston port opens at a predetermined point as the piston nears TDC. This is because steel or fiber reeds require some threshold amount of suction to open, so they likely shut at some point before the piston nears the end of it's stroke. At that point there's still a little suction, but no means of filling due to the closing/closed reed. By opening the CC near/after reed closure but before TDC, you can get better CC fill and therefore more power. My guess is the bottom of the piston skirt also serves as a timing edge just like the top: Very clever use of design features if this is so.

Again, this was common to piston ported snowmobile engines of yesteryear. Does this make sense?

Tim

BTW: This example shows there are many tricks available for deflector engines to help them approach looper power densities. Very interesting indeed!