2 speed marine transmission.

[sprink56]

Has anyone set up an express cruiser using this transmission? Seems like it would work bolted on a Velvet Drive before the prop shaft and enable a boat to get on a plane quicker by allowing the engine to turn at a higher RPM using a higher pitch prop to get on a plane then shift to a 1:1 ratio once at planing speed to slow engine speed for cruising and high speed operation.

This is the rig that offshore power boat racers use.

http://www.coanracing.com/Catalog.asp?ProductLine=XMT

Any thoughts on this?:huh:

 

[Sundancer]

I vote you try it and let us know!! Speed, rpm and gph curves before and after will be required!

 

[Lazy Daze]

Other than "hearing" about it, I really know nothing about it. But, what's your take on how much HP is going to be lost due to parasitic drag? In a high HP boat, I would think the loss can be overcome with extra HP - but what about in a low HP cruiser? Again, I don't know anything about it - it's just the first thought that popped in my head.

Or, is this thing set-up in such a way that there is minimal loss?

 

[Pietro]

Possibly the only benefit is easier maneuvering thanks to lower revolutions of the props.... :huh: and slightly more SHP if efficiency of transmission is higher than usual...:huh:

It's difficult to understand the advantage if the prop's pitch does not chance...:huh:

I believe ZF did something similar a few years ago, but it disappeared...

Moreover...I would not complicate my gear to have better performance when going onto plane...it's just .000000000000000000001% of the time!! :grin:

 

[Sundancer]

There used to be props that did the same thing. They'd switch pitch to give you a better holeshot and once the pressure was off the blades, they'd switch to a higher pitch for cruising. I'm not sure if the company is still around or not?

 

[Presentation]

There used to be props that did the same thing. They'd switch pitch to give you a better holeshot and once the pressure was off the blades, they'd switch to a higher pitch for cruising. I'm not sure if the company is still around or not?

One of the companies trying that was Mercury Marine. I think they are still around.

As far as I know, it’s not a dead issue, just dead for now. My understanding is R&D or any Merc capital investment must be recouped in less than 24 months or the money is not spent per current financial restrictions.

Merc http://www.saltwatersportsman.com/article/Boating/Mercurys-Amazing-New-SmartProp from the year....gulp....2001?


[youtube]http://www.youtube.com/watch?v=OEq-m6dFJJE[/youtube]

[youtube]http://www.youtube.com/watch?v=_H-yHcOQ6Xw&feature=related[/youtube]

 

[dpmulvey]

Actually Presentation, it's older than that. I was stationed in Italy in 1990 and made the trek to the Genoa Boat Show. A company had an aftermarket bolt on kit on display for Merc sterndrives. He told me because it was hydraulic, the EPA was giving him a hassle exporting it to the states. It was pretty slick.

 

[Presentation]

Actually Presentation, it's older than that. I was stationed in Italy in 1990 and made the trek to the Genoa Boat Show. A company had an aftermarket bolt on kit on display for Merc sterndrives. He told me because it was hydraulic, the EPA was giving him a hassle exporting it to the states. It was pretty slick.

Thanks you.

I was not trying to say when the concept of a marine version of a variable pitch prop started but rather showing that it has not yet ended.


Its my understand that development costs and projected production costs have not permitted Mercury from moving forward with the concept.

I remember reading a post from John (Hamption) where he had some exposure to a prototype mercury variable pitch prop.

 

[tobnpr]

I can only see it being of value in race boats.
Pleasure craft don't swing wheels with enough pitch to make it a big issue getting on plane (assuming the boat is correctly propped, and not underpowered), while a race boat that's got props with enough pitch to run 100 mph might have that problem- especially if the engines don't have enough torque on the low end to get her on top.

So while it arguably would allow a boat to plane faster, who would care enough to justify the expense (other than, a race boat)?

 

[sprink56]

I looked at the ZF set up and must say it is well engineered and thought out...typical German deal:thumbsup:...anyway the idea would be to spin a low numbered pitch prop at 1:1 to improve acceleration and throttle response at low planning speeds then shift to an overdrive like .6:1 to over speed that same prop to give you your normal cruise and top end speed.

The ZF looks like it could replace a BW Velvet Drive easily.

What started me thinking about this was the drive swap my brother and I did on his 23' Formula. We modified an Alpha II to match up to a MR-1 gimbal housing. The Alpha has a 1.62 gear in it compared to the 1.5 in the original No. 1 drive we replaced. Using the same 19" prop that boat...that is traditionally a slug getting out of the hole, jumped up on plane like a Bass Boat! We were spinning the modified 350 in his boat to 5500 RPM but were only running 35 MPH. I thought...as good as it jumps out of the hole, wouldn't it be nice to be able to accelerate like that and once on plane, shift to an overdrive to spin that same prop faster but drop the engine speed about 20%~25%. We ended up going to a 21" pitch and all is well....but it doesn't jump up like it did with the 19" pitch. It now runs out at about 55 GPS at 5200 RPM

This concept would be great on heavy Express Cruisers running in and out of rough inlets and in rough seas. The great throttle response would come in handy.

It's do-able...just wondering if anyone has done it.

Here's the link to the ZF set up. http://zf-marine.com/Transmissions/TechnicalDataSheet.cfm?DS=Description&GN=ZF_90_ATS

 

[Sundancer]

They are out there:

http://www.aerostarmarine.com/

There used to be a Land and Sea Torque Shift Prop too, but it doesn't look like the company supports it anymore. I can't find anything on their website.

Here's a Popular Mechanics article:

http://www.popularmechanics.com/outdoors/adventures/1276976.html?page=4

 

[tobnpr]

John,
Talk about German transmissions...
I just saw a show a few weeks ago on the Bugatti Veyron. Talk about a "transmission"!

Back on topic...

 

[sprink56]

Bugatti Veyron.....

Mike...the more I look at that thing the more I think it's time to finally go to flight school and get my pilot's license.:thumbsup:

 

[CSR_Admin]

Bump this thread in about 2 months and I'll let you know how it works. We have a ZF 2 speed in our shop right now that is going on my brothers diesel inboard Seacraft. His boat was always slow to get on plane so he's hoping thi$ fixes it.

 

[sprink56]

Bump this thread in about 2 months and I'll let you know how it works. We have a ZF 2 speed in our shop right now that is going on my brothers diesel inboard Seacraft. His boat was always slow to get on plane so he's hoping thi$ fixes it.

Jim,,,take some pics of this change out/modification. I think this could be a popular mod if it works out. Out of curiosity...I would like to see the math you guys use to determine gear ratio and prop pitch selection.

John F