Marathon Rules

[Matt]

Thanks for that.

[Mike Lloyd]

Originally Posted by Matt

So a 377 scorpion is ok?
But a +30 377 scorpion that's been rebuilt isn't?

http://www.mercurymarine.com/engines...orpion_377.php

Not quite the engine you would want to buy for offshore racing, unless you are a skier!
ML.
.

[Matt]

It looks like the 383 motor is illegal - not for any of the above mentioned reasons, but because I believe the intake & exhaust of the 383 are not the same as 377 scorpion and therefore stickers, block age/ancestry, block casting numbers become irrelevant.

In particular:
1. The 383 specifies tubular CMI headers and therefore contradicts the rules on exhausts
2. It looks like it might also have a different intake from the scorpion base motor (although I'm struggling to find any references to check against)

So while the short or long block 383 is likely legal as a rebuilt 377 (unless merc used a different spec/range of casting numbers), the package as offered by merc is not.

[Matt]

Do the rules specify it must be a bravo package/bobtailed etc. I don't think they do. Someone could have an engine from 1 manufacturer & a drive from another, right? As long as the motor comes from the "consumer" range, which in your link, I think it does.

Or are you saying the 377 scorpion is also illegal? http://www.sea-pro.com/mercurymarine...corpion377.htm
Possibly, as it could be a considered a "race" engine based on the above link.

Originally Posted by OldMan

http://www.mercurymarine.com/engines...orpion_377.php

Not quite the engine you would want to buy for offshore racing, unless you are a skier!
ML.
.

[Matt]

And yes, I know it's an old link and no longer in production.

[Matt]

Since the rules explicitly exclude the 525 package due to the exhaust without offering the option of downgrading them, this implies the 383 package with an exhaust change is still illegal. Plus - I "think" the intake might be different too.

Originally Posted by Jon Fuller

Exhaust rules would need to be strictly adhered to, that way the 400hp 383ci engine doesn't fit, at least not without an exhaust change, which would hopefully bring it's power in line with the 360hp models..

[Cookee]

Originally Posted by Matt

Since the rules explicitly exclude the 525 package due to the exhaust without offering the option of downgrading them, this implies the 383 package with an exhaust change is still illegal. Plus - I "think" the intake might be different too.

My understanding is that the 525 fits into Class B where this:

As an example, the Merc 525hp motor used in P1, has CMI headers with runner
lengths greater than 6” long, so these motors would not be permissible. The old Merc 500 carb,
had GILL/Merc alloy manifolds with common plenum, they would be acceptable, as would STD
Merc 496HO’s, or 502efi’s.

Doesn't apply to A,B,C, and C sport classes?

[Jon Fuller]

Originally Posted by Matt

It looks like the 383 motor is illegal - not for any of the above mentioned reasons, but because I believe the intake & exhaust of the 383 are not the same as 377 scorpion and therefore stickers, block age/ancestry, block casting numbers become irrelevant.

I don't agree. As I see it, the remanufactured 383 stroker, as supplied by merc reman, would be perfectly legal IF it's advertised spec for swept volume fell 'under' 6250cc, which it doesn't. Of course, you COULD run a single one in E class, being under the 6500cc limit. You could also run one 377 and one 383 in D class, as that amounts to 12,448cc.
Having different manifolds, or exhausts to the Scorpion, or more importantly the std 6.2 Bravo offering has no bearing, as it's still an engine offered to the public by a mainstream engine builder.
The 400hp variant has CMI headers, so that has another reason not to be allowed in D, but the 350 crankshaft hp(?) 383 Stroker has regular cast manifolds like the 6.2, so is fine, or would be if it weren't for the cylinder capacity being a smidge over the allowed, combined limit..

The rules state you can make internal modifications, such as cam, valves etc. this is more to simplify policing by scrutineers than anything to keep things workable, and the idea was, that the exhaust rule will keep a lid on things, and is relatively easy to police.

[Mike Lloyd]

The answer to all of this is for the TWG at the ORC to make a ruling PDQ or for someone to buy two of these engines, fit them and come to the first race where they WILL be protested. It would then be down to the scrutinisers and the Protest Jury to determine whether they are legal or not. Huge waste of money and time for anyone if the Jury determines that they are illegal just because someone wants an edge over the other racers in Class D..

Otherwise forget it and we can all get on with our racing without all this rubbish and angst.
ML.
.

[Jon Fuller]

Originally Posted by Cookee

My understanding is that the 525 fits into Class B where this:

As an example, the Merc 525hp motor used in P1, has CMI headers with runner
lengths greater than 6” long, so these motors would not be permissible. The old Merc 500 carb,
had GILL/Merc alloy manifolds with common plenum, they would be acceptable, as would STD
Merc 496HO’s, or 502efi’s.

Doesn't apply to A,B,C, and C sport classes?

A, B, and C-sport are 'free' as far as engine spec, as long as they meet capacity regs.

C-stock, D and E do not permit headers, and the motors must be based on engines that are mainstream production. that means the castings, manifolds (In & Ex) throttle body etc must remain as per the `OEM fitment. Though you can 'fettle' internally, those OEM parts.
For diesels, the Intercooler & Turbocharger must also remain OEM spec. (part Numbers etc) no parts can be changed. So an engine like the Goldfish D-Max, which has modified, or different turbo etc, is not permitted. Winding the pump up a bit on a Yanmar or similar is allowed, as well as gas flowing etc, so long as the components mentioned are OEM.

Re: the 383 Strokers, the big problem I see, As I said earlier, is that whilst I firmly think it doesn't fit, and certainly wasn't intended to, If someone arrives at a race with a pair of small blocks, and these small blocks have been 'de-badged', or indeed, re-badged, all the scroots can do is measure bore & stroke and look for std looking manifolds etc. If the bore measures 4.030", and the competitor says "Oh yes, we rebored these to +0.030", as per std Merc overbore, how can it proved either way, and distinguish between those have debadged to deceive, and those who have genuinely rebuilt their motor? So how do we police this??

[Jon Fuller]

Originally Posted by Matt

Since the rules explicitly exclude the 525 package due to the exhaust without offering the option of downgrading them, this implies the 383 package with an exhaust change is still illegal. Plus - I "think" the intake might be different too.

Rather than being 'explicitly excluded' I think the rule wording on the HP525 is using that engine as an example as a comparison against the 'similar' HP500, which has common plenum manifolds.

If some of this stuff is going to get altered, another wording change could maybe go along the lines that the old T-class rules did, where you can change exhaust manifolds, so long as they meet the runner length rule. In NPC and T class, that was because pattern replacements were much, much cheaper than OEM replacement, so it was considered fine to use aftermarket manifolds, as long as they met the requirements. I don't see why anyone would object to that in Marathon.

Looking at this picture of the new Merc 502HO motor, That wouldn't conform to C-stock, or D either, as the exhaust manifolds appear to have runners exceeding 6' in length. Would need to see one in the flesh to be sure.

[OCRDA]

Heeeeeeeeeeeeeeeeeelp !! WHY was this allowed to get so complicated !!

Its the 50th aniversary of Cowes this year !! What was fundamentally wrong with the classes back then ?? Classes 1, 2, 3, 3d 3c cruiser etc. I am on the TWG but please dont ask me to help sort this mess out.

Bob

[Jon Fuller]

Originally Posted by OCRDA

WHY was this allowed to get so complicated !!

Bob

The same reasons that you claim were fundimentaly wrong with 2litre OCR, speeds need to be kept sensible, costs need to be kept sensible, safety needs to be kept sensible and it needs to be a level playing field.

And it isn't particularly complicated given the size of the task., the introduction of the 383 has complicated the issue.

If we only had to choose between a 130 Yam and a........well, a 130 yam, I expect our rules would look as simple as yours, but it simply cannot be that straightforward while achieving the requirements stated above, with so many classes (more than I wanted remember) and so many variations on the theme as far as power options go, inboard and outboard.

[Jon Holmes]

Originally Posted by Jon Fuller

speeds need to be kept sensible, costs need to be kept sensible, safety needs to be kept sensible and it needs to be a level playing field

Totally agree with the three points above which, in my opinion are the most important criteria for the future of the sport.

[Jon Fuller]

There are 4 points above!

[Jon Holmes]

Yes Jon,

But I only agree with the first three as they are achievable.

As all men are not equal i feel it would be impossible to achieve your fourth point of a level playing field, hence my comment.

[Matt]

Aint the apparent length in the runners due to the cat, and not actually individual runners at all?

Originally Posted by Jon Fuller

Looking at this picture of the new Merc 502HO motor, That wouldn't conform to C-stock, or D either, as the exhaust manifolds appear to have runners exceeding 6' in length. Would need to see one in the flesh to be sure.

[Jon Fuller]

Originally Posted by Jon Holmes

Yes Jon,

But I only agree with the first three as they are achievable.

As all men are not equal i feel it would be impossible to achieve your fourth point of a level playing field, hence my comment.

But we are talking technical boat rules, not rules to level the good, the bad, or the ugly driver. That, I agree is impossible.

[Jon Fuller]

Originally Posted by Matt

Aint the apparent length in the runners due to the cat, and not actually individual runners at all?

You might well be right, but what made me look at the picture, was reading this bit about tuned runners on the merc site. Of course, it doesn't mean they'll exceed the 6" maximum, we'd need a proper look.

If they turn out to be just over the current legal length, as it's a super clean engine and the std pleasure offering from merc, when they start to appear, it might be necessary to include them, so long as they are unmodified and still have the cat installed/operational. we'll cross that bridge if/when we have to. Just a wee tweek to the rules, to include up to date equipment as it becomes available.

As it would only likely affect single installations in Class D, I don't think it'll be a common, or frequent issue.