Outboard Exhaust Tuning - Who Did It Best?

**FMP** · 08-23-2019, 04:24 PM

Originally Posted by Dave S

JMO.....A Mk 20h.... cornpopper......Eh? wadda say?

Was thinking that he mark40 , I seem to remember a story of how Merc at the time was discovering new found power in the ex tuning.

**FMP** · 08-23-2019, 04:31 PM

Originally Posted by Chaz

I was thinkin more along the lines of the 3.3 and 3.4 blocks. They'realready done, it takes quite a bit of effort to turn a 3.0L Merc into a 3.4~ 3.6 deal. But that's the direct way to serious steam ..

FMP

you need to crack an egg to make an omelette

Chaz = Yup, that what I thought ....

You start a thread on it, tell us all what the intended use or goals are and then maybe we'll trade paint or ideas.

**FMP** · 08-23-2019, 04:48 PM

Noteworthy

**Chaz** · 08-23-2019, 05:02 PM

Originally Posted by Dave S

JMO.....A Mk 20h.... cornpopper......Eh? wadda say?

I say I was 2 years old when they sold the last run of them in 1960 .. I do know where there is a museum with some really pristine resto's ...

**Chaz** · 08-24-2019, 02:00 PM

Originally Posted by BarryStrawn

I believe Chaz is saying he did/does it best. Which is the subject of the thread. All the other contenders left S&F years ago but you can see many of them in just a few weeks at Jasper.

Well B.S show me where I said "I was the best" .. Thats right nowhere

Don't show three round holes running into a flat plate less than an inch away with a kinked up mess leading away circa 1914 and call it the best ever .. you might believe it , me not so much ...

The guys in Jasper who win class .. They call them "World Champions" right ?

If so, I very grateful to just be a small spoke in the wheel of a few of their wins

And you .. ???

Originally Posted by Chaz
I was thinkin more along the lines of the 3.3 and 3.4 blocks. They'realready done, it takes quite a bit of effort to turn a 3.0L Merc into a 3.4~ 3.6 deal. But that's the direct way to serious steam ..

FMP

you need to crack an egg to make an omelette

Chaz = Yup, that what I thought ....

FMP

You start a thread on it, tell us all what the intended use or goals are and then maybe we'll trade paint or ideas.

You seemed to be interested when you thought I was going to show you what I feel is necessary to move the volume of exhaust required to support 3.5+ Litres ..

Omeletts, pictures of a motor that got the axe when I was in High School, new threads necessasary .. Intended use .. really ??

**BarryStrawn** · 08-26-2019, 11:16 AM

Chaz - No offense was intended.

Some small parts I figured out and fabricated have been used by guys with World Champion after their name. But nothing to brag about.

**Markus** · 08-29-2019, 06:45 AM

Originally Posted by powerabout

so there is more HP potential from the omc 3.0 than a Merc 3.0

That's what Wayne Taylor, who played a lot with both designs, said when I asked him.__PRESENT

**powerabout** · 08-29-2019, 07:01 AM

I still dont like the omc exhaust on the 90 looper
I do like the g2 exhaust, that has some big potential

**Chaz** · 08-29-2019, 08:31 AM

Originally Posted by powerabout

I still dont like the omc exhaust on the 90 looper

I saw one the other day that might change your mind ...

I do like the g2 exhaust, that has some big potential

I live about 2 miles down river, from what's left of the test center. General consensus of the starboard / starboard from within was ...

Might have been a bit of old dogs, new tricks. But I don't see too many of them in the sea of Yamaha's around here ...

**Motv18** · 08-29-2019, 09:00 AM

Just to stir the pot,

seven marine with shorties. But it’s basically an inboard on a transom bracket.

**powerabout** · 08-29-2019, 09:05 AM

Originally Posted by Chaz

I saw one the other day that might change your mind ...

I live about 2 miles down river, from what's left of the test center. General consensus of the starboard / starboard from within was ...

Might have been a bit of old dogs, new tricks. But I don't see too many of them in the sea of Yamaha's around here ...

funnily enough the exhaust on the 31m is on stb, they said less exhaust dilution?
G2 did the opposite so it must be for airflow in the crankcase?

**Markus** · 08-29-2019, 09:25 AM

Originally Posted by powerabout

I still dont like the omc exhaust on the 90 looper

Wayne liked it.__PRESENT

**powerabout** · 08-29-2019, 06:34 PM

too many 90 degree turns
photo Freddie Webb

**Chaz** · 08-30-2019, 09:14 AM

The bottom two make a 180* ...

They did the best they could to make all three "primary runners" the same length.
Adding cross sectional area to the center pair, while not as good as length adds volume to equalize the three.
Making a turn at the point of intersection tends to keep a bit of the charge going in a straight line rather than make the turn, but then they did what they could in the space they had to work with .
To make the 3 into 1 deal truly work, the runners need to merge like the onramp to the highway. That way they will all pull and return evenly ...

Power , ya know there are better ways to cut the back off than usin an "Alabama blue wrench" ..

**FMP** · 08-30-2019, 02:26 PM

Some vehicles have a little more room and display a more obviously tuned system. The photo shows a BombardierSki-Doo snowmobile powered by a 110HP, 3 cylinder 700 cc Rotax engine. This vehicle allows room for a larger more complex system. The exhaust manifold still allows for the short distance between exhaust ports for a pulsewave, but adds a much larger expansion cone to a provide stronger negative wave, and very possibly it also augments the positive wave at certain speeds.

OMC built the V6 above to have more equal distance spacing between the tuned pairs vs an open chest via the "primary runners" lengthened two short distances.