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Tunnel Mounted Pod Drives?

Discussion in 'Technical Discussion' started by theav8r, Jan 14, 2012.

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  1. AMG, Jan 24, 2012
    #21
    AMG

    AMG YF Moderator

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    If you think of what a powertrim does to the boat, this is the same but sideways.
  2. PacBlue, Jan 24, 2012
    #22
    PacBlue

    PacBlue Senior Member

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    Captaintilt, I think you have it well said in a nutshull: Zeus required a unique grommet design for the hull/lower unit interface/seal that could not infringe on the IPS' patented design, hence the selection of a flat surface which drove the tunnel design. Sea Ray also influenced this design direction, as they were some of the initial test platforms and obviuosly had their trademark flat tunnels. I recall these early discussion points with Rick Davis, who led this development project for the CMD team when all this fun started. He has since moved on to start Seven Marine, a new V-8 high hp outboard manufacturing company.

    It has been my experience that both these type of Pod installations do not like rocker, but prefer hook. I would not spend too much time trying to determine any merits for lateral thrust, parallel to a waterline, or "out of plumb with gravity???", as one is a pusher and the other is a puller. Hull loading and CG location will be the designers driver.

    I'd be curious if anyone knows the uptake for the Zeus option on the Cabo 40 versus conventional shafts - is the buying public making their preference clear? :)
  3. captaintilt, Jan 24, 2012
    #23
    captaintilt

    captaintilt Senior Member

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    Thanks PacBlue, I was fortunate enough to work with Rick Davis quite a bit on this project, and was a little surprised to see him take on the venture of starting Seven Marine, but am sure he will succeed.

    In reference to the Zeus / IPS Rocking motion, I noticed, and again, I'm not an expert by any means, but the largest difference between the IPS and Zeus versions is that the Zeus drives utilize a ZF transmission with a trolling valve in it. It allows for the clutch to "slip" and slowly turn the props and when the Captain applies more joystick, the clutch engages more for more power to the props. The IPS boats, (and they may have changed by now) were built more like a sterndrive, in that you were either in gear or out of gear, no in between. This threw a lot of Captain's / Owners off at first and took them a lot of time to get used to. I would have to say that the biggest difference in handling was between 2 Tiara 38 Opens that were utilized, one with Zeus and one with IPS. I had logged jus shy of 500 hours on the helm of the Zeus Tiara within a span of about 5 months in Charleston with CMD and the engineers from Tiara and hopped on a 38 Tiara while at my parents house in the Great Lakes and it was a night and day difference and took me about 30 minutes or so to get adjusted to the IPS joystick and maneuvering / how much lateral motion you could use when docking beam to a dock.

    I looked at my notes last night and forgot about the 7 Cobalt 46's that were built with the Zeus drives, it was a great boat with phenomenol amenities, but it was extremely heavy for the QSB 5.9's, (we actually tuned them to about 470BHP versus the traditional 425 to 440 and it averaged about 1mpg at 28 knots, but they were extremely expensive and never really took off to the market. I will say that I delivered the boat from the Boston boat show to Baltimore and stopped in Newport to drop off a Cummins employee, and it really turned some heads and had the crowd at Bannister's Wharf looking, and staring at the drives in the water wondering what they were. As it turned out I was there a a few weeks later for a Grand Banks expo doing demonstrations on a SeaRay (the 41EU wasn't in America yet) and ended up taking a lot of the locals out for rides to show them the system. What a great group of individuals and it was my second of many visits to Newport / New England by water, what a great place to operate!!!!!
  4. Capt J, Jan 24, 2012
    #24
    Capt J

    Capt J Senior Member

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    With Brunswick owning Searay, Cabo, Hatteras as well as Mercruiser. Mercruiser is part of the CMD joint venture which means Cummins Mercruiser Diesel. Brunswick devoted a lot of hull engineering and adapted several boats to work with the Zues system. The 40' Cabo and 48' Searay specifically. Cabo also has a 36' ZF pod boat which isn't nearly as smooth as the Zues system. The utilization of the trolling valves makes finite maneuvers very easy. Cabo has sold more than a few 40 Zues Boats which are faster than the largest MAN powered boats. The 800 Mans propel the 40 to a 31 knot cruise at 62 GPH. The 600hp Zues will cruise at 31-32 knots at 43-45 GPH, a large efficiency difference. US boats tend to favor the Zues system, boats going to foriegn countries and out of the way places are sticking to the less complicated (electrically mainly) traditional shafts and drives and also the closest engine dealer has a preference as well on purchasers.
  5. captaintilt, Jan 25, 2012
    #25
    captaintilt

    captaintilt Senior Member

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    I agree, the Cabo Zeus boats are a lot more efficient with the QSC 8.3's than the MAN powered boats. I haven't heard of the sales statistics with them going overseas or down island. I do know that the recent developments of the computer upgrades and coding for the "brains" of Zeus, it can be very easy to upgrade / downgrade as necessary by utilizing a jump drive or laptop with a USB cord. It will be interesting to see how things are handled now with the dissolving of the Cummins / Mercury Joint Venture. I have heard that Mercury will handle the high speed, low HP diesel engines that was coming from the Volkswagen block, and Cummins will maintain the Quantum series. I don't know who will be handling the Zeus drive system, IMO Cummins should and Mercury should stick to Outboards / Sterndrives.
  6. Capt J, Feb 25, 2012
    #26
    Capt J

    Capt J Senior Member

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    Ok, I got some insight to why the pods are usually mounted in a tunnel. I just ran a 40'< boat with the ZF pods that are not tunnel mounted, and I have run a few of the same boat with traditional drives. The boat at cruise turns normal if you turn very slowly (like a typical autopilot turning speed if you hit turn 10 degrees), if you turn just a touch tigher the boat leans way over (like if you turned the wheel hard on the traditional drive boat) and turns extremely tightly. There's no in-between it turns slightly at cruise or the boat leans way over and turns sharply........ The same company's larger boat with the ZUES drives mounted in tunnels doesn't do this.

    Anyways, I talked to one of the engineers and he explained that anytime the drives are mounted on the deadrise instead of straight up and down (usually requiring tunnels) it does this. It's much more preferably to have the drives mounted straight up and down for both turning at cruise and stability while walking the boat sideways (causes more rocking) and such with the joystick at rest. They didn't re-design the hull at all on the ZF pod boat, just mounted them in there.

    The ZF pods seemed to react similar to the Zues, but the zues seemed to be a touch better in maneuverability and finesse. I do like the smaller physical size of the ZF joystick over the Zues joystick, and I like the fact that you can get CATS or other engines with the ZF.
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