offshore snout

[sean1982]

i have noticed quite a few people have cut the end off the snout on the offshore mids,mainly in the US, does anyone have any idea why? other than noise?
cheers

[Jay Smith]

In drag racing I flip the down housing upside down and mill 2 1/2" X 6" slots under the housing so that the exhaust has a straight path down and OUT , the more exhaust that is not directed easily out gets forced through the carrier and can make the prop slip % more...

Jay @ JSRE

[sean1982]

Is it worth doing then?

[larby]

I wouldn't say so, no.

The sound is awesome, but much the same with it not done. At least with it not done, you can plug the exhaust if you want for performance/noise reasons. Can't do this once you've lopped it off.
Whilst the sound is great, it will most probably make your head explode after more than 30 mins, whereas with it as standard, you get that nice 'rar,rar,rar,rar,rar' noise as you skip through the waves.
I also very much doubt you'd see any difference whatsoever in performance.

Even coming from someone who obsesses about the sound and volume of engines, i wouldn't.

Also, they're bringing in noise restrictions all the time over here, especially in herm. May end up being 'too loud' in a couple of years, with no easy way to sort.
Plus i think it looks gash as hell.

James

[baj666]

thats what i love about my motor...the sound of the above water zorst ....why did mercury make em like this?? was it performance or just the era when looks and noise was everything

http://www.youtube.com/watch?v=BWJ_3syKB30

[sean1982]

have you had yours cut?

[gar163y]

I thought they were cut off so you could get your hand in easier to undo the Allen bolt holding the gearbox on.

[Jay Smith]

It WILL pick the motor up and make the prop more efficent .. Been there and done it ! DUNNO about offshore racing but drag racing it WILL help..I do ALL my customer's 15" mids that way... ( I'm refering to the slots under the mid, Leave the snout alone and do the slots )

Common sense would prevail that the exhaust fighting to make an L or a J hook to leave the motor via a snout would hinder the flow rather a path that was straight down and out..

Jay

[Jay Smith]

In conclusion the spent gases that are hindered in any way from leaving the down housing in a straight non obtrusive path is FORCED through the carrier area, thus air rating the prop causing the prop to be force to bite and move MORE bubbles and less clean hard water..

Leaving through an L or J shaped exit path ( OS Down snout ) instead of going straight down the path of least resistance will cause the gases to be force through the carrier , if its slotted it goes straight will little obstruction of flow..

A common sense call IMO ... It's worked for me and my customers for years.

Cheers,
Jay

[larby]

Jay, whilst I don't disagree with you, and I'm well aware you know way, way more about the subject than me, I'd say there's more to it than that in offshore?

For starters, some props benefit from the added aeration given by the exhaust gases exiting over the prop, and many of the props used by racers I've seen are often 'through hub' design, thus would be unaffected by the exhaust gases?

As far as I'm aware, 2 stroke engines require a very specific amount of back pressure in order to operate to their fullest potential. As the intake and exhaust stroke are the same thing, this small pulse of back pressure ensures as little as possible of the mixture being taken in goes in one hole and out of the other. I know there's more to it than that, but nothing too relevant.
I'm assuming an outboard uses the hollow leg as it's expansion chamber, so I'd have thought giving the gases a much easier route out could have a negative effect akin to removing the silencer part of a scooter exhaust? Or does the tuner pipe take care of this?

Lastly, and partly going back to the first point, having the standard setup allows you to tune the amount of gases exiting via the snout or the prop with use of a plug. This way you can tune the aeration required for a certain prop (say if you were running a very tall prop on a calm day, but still needed good pickup out of tight corners), or possibly even tune the back pressure for a certain engine setup?

There is also, more and more these days (much to my dismay), the subject of noise. Over here and in the rest of the world, people are cracking down on this kinda thing more and more. Cutting your snout not only makes the engine a lot louder to an observer, but removes the ability to easily silence it with a plug, should it be required for noise regs. I know that I'm buying some silencers for my V8 for the herm race. Not cos I don't like the noise, but because upsetting everyone who doesn't share my passion for it won't get the sport anywhere.

Of course, I could be totally talking out of my arse here as I'm yet to have much real race experience, hopefully that'll all change soon! Not disagreeing with you at all, just really enjoy an intelligent conversation about a subject I love! It's all a big learning curve!

Cheers, James

[Jay Smith]

James,
I or my customers could care less about the noise, these are race engines most not for recreational use. The first Mercury 260's were cut exactly as I have described it was called a bass mid section and had 10 total 1/2" holes cut in the leg at the base of the mid and worked well...
While moving toward winning several World and High points Championship Titles in back to back years in outboard drag racing I did extensive testing with down housing exhaust exits points as well as prop bite.I found a combination that was successful . I started with a completely blocked off path through the carrier and that failed totally . I then started to add spent gases in a measured systematic way through the hub and found that the more spent gases that was allowed through the carrier and out the hub across the prop the quicker the boat would reacted to throttle. BUT I also found that if the carrier "TOOK" the amount that was vaccumed through gently and was not forced fed it worked even better with the slots cut the carrier gets what it requires with the amount of vacume the prop is sucking through.

99% of the time when I suggest something its not from some theory or what "could" work its from many hours of testing and trial and error and a success path is achieved that I am willing to share with an interested group, multi cylinder 2 stroke outboards exhaust have VERY little in common with a single engine expantion chambered engine such as bikes or even any expantion chambered systems its simply nothing like that system, its like comparing an apple and a pecan.Also most custom tuners shape and length advantages come into play and are to an advantage ONLY if the stock OEM one is mis engineered ( such as the long one on a 150 Merc ) OR the engine is able to turn 9500 RPMS to more. My Drag race motors turn over 11,000 rpms and certain custom tuners on even those engines can move around or alter the power band only slightly with shape and length alterations. ....

Cheers,
Jay

[larby]

Cool, so i was totally talking out of my arse then!

At least now I know for next time, it's not a subject I've ever really been able to read much about before! Thanks for answering all the points for me Jay, most wouldn't be happy to share their hard work so willingly!

Cheers, James

[Jay Smith]

Thanks James ,
I'm NEVER unwilling to share my knowledge on success OR failures that I have experienced, I feel that is what these forums are for to interact and help one another and IF I have walked that path to failure I feel its my duty as a part of the sport to warn a person of inpending failure as well as success..

I wished when I was starting out racing I had someone on a forum that cared enough to sway me away from some costly errors... I Would have allot more $$ in my pocket...But I am a pretty quick learner and VERY mechanically inclined and own my own machine shop....

Cheers,
Jay