Gear Ratios for Speedmaster #3's

[Pash 1]

Originally Posted by Jim Brooker

I see all the information you are getting, but to start with are you going for staggered engines, if so the drives must be remounted at 18ins apart and the same hight as now for MK 3, or remount the transon plates, the plates are the same for MK 3 & 4 drives, if you are going for new drives, buy Mk 4 drives 1.40:1 or 1.50:1 and set the drives high, or on box's it well run better.
It all depends on your engine power if you bhp is low 1.40:1 would be better than 1.50:1.
You must buy drives MK 3 or 4 with long shaft, I have a pair of new K 18x28. 3 blade.19 splind props you can try, when you get to that stage.
I use to rebuilded all the drives, on the diesel boats the MK 3 lasted between 3 and 7 hours, the Mk4 drive a little longer. petrols up to 600 bhp 15 to 25hours racing.
I hope this is to not to much information, if you like you can ring me or I am in the South of the Uk in April.

Thanks Jimmy will pop down and see you when your back in the UK if thats alright

[Jim Brooker]

Martin. There is no point in trying to run with 1:1 drive ratio the prop will be to small to work, like couple of egg whists, all you will get is cavition.

[Jim Brooker]

More porblems, are the MK3 drives you have the original ones when the boat had the Sabres in it, if so you must have them rebuilt because they are set up to run anti-clockwise, the lower gears are loaded the wrong way, they must be reset for clockwise rotation.
Big if you had 600bhp at 5400rpm 1.50:1 ratio,27x18 prop,you should to get 82mph

[Jon Fuller]

Originally Posted by Jim Brooker

More porblems, are the MK3 drives you have the original ones when the boat had the Sabres in it, if so you must have them rebuilt because they are set up to run anti-clockwise, the lower gears are loaded the wrong way, they must be reset for clockwise rotation.

Is this because the step up boxes reverse the engine rotation?

[Matt]

Sounds like the warlord drive might have solved half the problem - but I understand it might be sold?

[Jon Fuller]

Yes, it was offered a while ago, but is no longer available.

[Jim Brooker]

Yes Jon it was because of the change of ratation with the Sabre step up box's, it would have been easier to put the Sabres back in her.

[Pash 1]

I knew this wasnt going to be easy..

[Jim Brooker]

I am sorry but what is !!!!

[Pash 1]

Jimmy I'd rather know the "Not so good news" now rather than when its too late and we end up doing 82 mph in reverse

[Jon Fuller]

Originally Posted by Pash 1

we end up doing 82 mph in reverse

That's not actually what he means. He's refering to the adjustment of the backlash of the gears, or rather lack of it. It's set differently, depending on which way you intend turning the drive. Your boat would go forward, but gear failure will happen prematurely if it's set up to be running in the opposite rotation (for Sabres)

As I said in an earlier post, finding someone to do the job, who's equiped in all the required ways could be a struggle in this country.

[Matt]

Gotta be worth considering re-rigging for bravos - esp if the engine bearers etc aren't in yet?

[Pash 1]

Which Bravo's Matt/Jon ?

[Matt]

Do you mean whose, or which spec? Who's - well you had a pair, dunno if they've sold. Which spec, Bravo 1's, but depends what's available as to which exactly.

This would mean repairing/the transom to fill the mk III holes, so still loadsa work, but at least it'd mean a currently supported, maintainable set of drives.

[Pash 1]

Originally Posted by Matt

Do you mean whose, or which spec? Who's - well you had a pair, dunno if they've sold. Which spec, Bravo 1's, but depends what's available as to which exactly.

This would mean repairing/the transom to fill the mk III holes, so still loadsa work, but at least it'd mean a currently supported, maintainable set of drives.

The ones I had were old circa 1990 i think and to be honest didn’t look up to handling the power - but they did! one of the prop shafts looked like a curley wurley - all twisted...

[Jon Fuller]

Not sure if Bravos, or their gimbles would be up to 500+hp on such a big boat (where they can be truly punished)

HP gimbles & XR's might be ok, but they're not so easy to find, and still not guaranteed to be up to it (especially if Johnny H is slow on the sticks).

The gimbles & drives on Swipes were the best part of 25k with the vat

[Matt]

Fair point, but at least it's an upgradeable platform within the Bravo family/style, and as Tony reminds me regularly, the bulldog came with a standard bravo.

8K for gears, plus shipping (maybe both ways across the atlantic), labour & other parts to rebuild. Ouch!

[Pash 1]

Originally Posted by Matt

Fair point, but at least it's an upgradeable platform within the Bravo family/style, and as Tony reminds me regularly, the bulldog came with a standard bravo.

8K for gears, plus shipping (maybe both ways across the atlantic), labour & other parts to rebuild. Ouch!

mmmmmmmm ouch - I can get the gears for a lot less than the circa £8K but it's still a case of having them fitted.....

[Jon Fuller]

As per the link TD gave, 3500 bucks, for a complete SSMIII 1.5:1 upper, new. I know what I'd do.

And I'm sure the std shimming on new ones would be done on the assumption of normal rotation. The shimming Jim is talking about would normaly have been done in the days when the left & right motors were handed in their rotation, ie, one engine ran backwards to give the propeller counter rotation. I think this was done to give true balanced tourque etc (as drives were/are available as handed units) and also done for the arnesons, where handed units weren't available.

[Pash 1]

Jon what about these?

http://www.offshoreonly.com/classifi...o27252-en.html

Would they fit the bill on her??