drive ratio

[Coolerman]

For Ryan, I would start at even with the bottom of the bottom because the drives are further apart.

[Ratickle]

Are you redoing the transom? Or just using the current setup with shorties to get the height you are thinking of?

[ryan9154]

Using the current setup The reason I'm not big on the arnesons is the tranny for one reason found out it takes about 15% more hp to spin arnesons than a bravo and I can't find out if the helm change are the same size 37 degree swivel fittings and line diameter if not all new lines no fun with a inner liner I wish bill from xpower wasn't on crack (35,000)those drives would be perfect -5 that would put me about even and a great guy to talk with hope he's at maimi boat show so we can talk

[Ratickle]

So you are saying if you go with the minus 4 IMCO, (Which would be the minus 3 lower and minus 1 mid), you will still be 1 1/2 inches below the bottom of the boat directly in front of the drives???????


Or am I reading your earlier post wrong??????

[offshoreexcursion]

Where did you find out that a arneson takes more hp to spin than a bravo? Does a bravo take less than a SCX4 then? So what is the SCX4 vs the Arneson? Yes X-power is sweet just overpriced. Why hate on trannies, all new fast boats have trannies.

Coolerman, What is your opinion on trannies?

[Coolerman]

A trannie will eat up more power (not sure about that 15% # tho....), but I haven't heard of anyone putting arensons on and loosing speed unless the boat was improperly setup/dialed in. As far as drive heights go, it sucks, but you just have to try everything if you want it perfect. Staggered boats will set them higher than side by side boats.

[Ratickle]

I'm doing some double checking, hopefully will get some very accurate input but, from everything I recall reading (and can find quickly to back it up):

A typical transmission in a V-Drive or Stern-Drive boat loses about 3% to 5% of the engine power.

The single 90 degree drive direction change in an outboard loses about 7% to 10% of the engine power.

The double 90 degree drive direction change in a stern-drive loses about 12% to 20% of the engine power. This is one of the reasons you see a 525 Merc engine dynoing at around 600HP at the crank. Merc rates them at the propshaft.

Now days, the wet drive vs the dry sump drive is reducing the parasitic loss of a stern drive. The parasitic power loss from the wet drive is almost the same as the loss from a real good transmission (allegedly).

Outboards and stern-drives have an advantage from the thrust angle vs an inboard or Arneson. But not that much advantage over the Arneson. So, the Arneson (or comparable surface drive), has the least total loss of any current system. Less changes in direction vs outboard or IO, closer to optimal thrust angle vs inboards or V-Drives. The total loss of an Arneson with a crash box has to be almost nil.

Now, pick me apart........

[Ratickle]

From BAM.

With the success of dry sump drives, and almost universal use of dry sump oiling in all forms of motor sports it became obvious to us that a dry sump transmission was the next logical step. By separating the lubricating oil from rapidly moving parts, dry-sump has been proven to increase prop shaft horsepower, increase boat speed, reduce temperature and extend operating life. Testing on our digital transmission dyno confirmed an additional 36% reduction in parasitic loss (at 6500 RPM) over the %38 improvement provided by our regular CYBORG. The most extreme application to date has been the 4 engine Nor-tech cat "Warbird". Two engines on each side are coupled together through 1 CYBORG Dry Sump and a Mercury #6 drive, 1700 Horsepower per transmission!

[Coolerman]

Nice find Paul! Here are some more #'s that merc recently published.

http://www.mercuryracing.com/blog/st...han-you-think/

[Ratickle]

Nice Jason......

[Coolerman]

From BAM.

The most extreme application to date has been the 4 engine Nor-tech cat "Warbird". Two engines on each side are coupled together through 1 CYBORG Dry Sump and a Mercury #6 drive, 1700 Horsepower per transmission!

I think we'll need some better transmissions with the new motors this year...... lol

[Ratickle]

I think we'll need some better transmissions with the new motors this year...... lol

Call Mark and tell him he's roughly 1000 hp short per side. Should be a good test for the trans capacity......

[Coolerman]

Call Mark and tell him he's roughly 1000 hp short per side. Should be a good test for the trans capacity......

Marc has the 72-LPH. Supposedly good for 2500ft lbs..... I haven't seen anyone using them yet or heard of any feedback whatsoever.

[Rik]

Using the current setup The reason I'm not big on the arnesons is the tranny for one reason found out it takes about 15% more hp to spin arnesons than a bravo and I can't find out if the helm change are the same size 37 degree swivel fittings and line diameter if not all new lines no fun with a inner liner I wish bill from xpower wasn't on crack (35,000)those drives would be perfect -5 that would put me about even and a great guy to talk with hope he's at maimi boat show so we can talk

I do not know where you got your figures but they are not in the ball park. The BAM tranny consumes about 9 hp and the Arneson consumes about 1. Not bad at all. As for the helm unit, all helms are physically the same (in this genre of steering systems) and use a standard dash 6 hose so there would be no need to re plumb the boat.

[Ratickle]

Hey Rik,

How did you get the numbers on the Arneson?

[Rik]

I called and asked BAM what their dyno says the transmission requires and I know the rolling torque the Arneson requires.

[Ratickle]

I called and asked BAM what their dyno says the transmission requires and I know the rolling torque the Arneson requires.

Thanks. Their machine is sweet. I'm not sure anyone else measures the losses like they do.