1977 Hydrodyne Tournament Skier 18 OB Rebuild

Discussion in 'Hydrodyne® Boats' started by barefootrocker, Dec 15, 2014.

  1. barefootrocker

    barefootrocker Hydrodyner

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    Dec 1, 2014
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    Location:
    Central Wisconsin
    Ski Team:
    CWWSST
    Why do you say yellow (or gold for that matter)? The colors are tan and dark green, to match the upholstery. Was there a green and yellow color scheme at one point?
     
  2. kevinb

    kevinb Elite Hydrodyner

    Joined:
    Sep 10, 2006
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    459
    Location:
    Brookfield, WI
    Boat Model and Year:
    1985 HD 20' I/O 350 (Yep I/O Boat #2 of maybe7?)
    Ski Team:
    NA
    Thinking NFL as in Green and Gold:).
     
  3. barefootrocker

    barefootrocker Hydrodyner

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    Location:
    Central Wisconsin
    Ski Team:
    CWWSST
    Ahhh I see. Yeah I'm a Packer fan, but the preseason I can leave, too much skiing to be done yet!

    Well, trip number two had some noted improvements.
    -Gauges are all working except for temperature, still poking around on that. But this time out we had water the entire time and no apparent heat issue.
    -Started and ran like a top. Water was calm and quiet so we could finally give it a good ride to get a sense of what we had.
    -Took a few hard turns to get a sense of the handling, and it's surprisingly good. Handles much better than our clubs' single rig 20.
    -Ran the boat at speed and peeked at the cavitation plate with the motor trimmed level, looks to be just barely below the water's surface, so a workable height. We could only trim a few degrees at speed before cavitating so we won't be going any higher, but it cornered well and the holeshot was firm and planted, so I'd say we're all good.
    -The prop we were running was the stainless 3 blade 23p that came on the engine. On paper didn't seem a good fit for the engine and boat, but I was pretty surprised at the the numbers we had. 5,200rpm (Mariner 175 EFI wants 5,000-5,600) and 52mph GPS. Couldn't believe the thing turned that prop that high. Leads me to believe that a good cruising prop would be a 3 blade SS 21 pitch, and pulling prop a 4 blade SS 19 pitch, in an ideal world. For now, we're just going to leave the 23 on and see if it'll pull me on a slalom deep start. I'm about 99.9% on slalom deeps, but I'm also 240 lbs, so let's see what we got!

    Crummy quality, but here's a video for proof of life:

     
  4. RiverRat

    RiverRat Hydrodyne 18 Specialist

    Joined:
    Sep 30, 2006
    Messages:
    508
    Location:
    Shoreview, MN
    Boat Model and Year:
    1971 Baby Dyne
    Ski Team:
    Twin Cities River Rats
    If your cavitation plate is below the water at speed, you may want to consider raising the motor a hole or two. This will give you more speed, more room to trim for a smoother transition, and a smoother table.

    Your thoughts on props seem reasonably close to what other have settled on as well. For mainly skiing, somewhere around 17-19 pitch works great for that boat. The lower pitch prop will give you better pull out of the hole and easier speed control, especially at low speeds. Some dealers will let you demo certain props, so that may be something you could try if you want to test some out. Most props these days are bow lifting props (lots of cup) for the bass boat crowd. That is the opposite of what you want. Try finding something that is more of a stern lifting prop. This will keep the boat flat coming out of the hole and while pulling at low speeds.

    And you are correct that the handling on the 18' is better than the 20'. More like a sports car than a family truckster.

    Great looking boat. Have tons of fun with it.
     
  5. barefootrocker

    barefootrocker Hydrodyner

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    Location:
    Central Wisconsin
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    CWWSST
    Right now we can only trim a little bit (a few degrees, +3mph or so at around 30mps) before cavitating. Wouldn't raising the motor make that even worse? I'm not visualizing how bringing the prop closer to the surface would reduce the chance of cavitation.

    We are taking the Dyne up north for the weekend, and taking both props, so we'll get to try out both. And somebody will finally be skiing behind it! Hopefully we'll be doing some barefooting, slaloming, trick skiing, running with a fully loaded boat, who knows what else. I hope we can put it through its paces!
     
  6. RiverRat

    RiverRat Hydrodyne 18 Specialist

    Joined:
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    Location:
    Shoreview, MN
    Boat Model and Year:
    1971 Baby Dyne
    Ski Team:
    Twin Cities River Rats
    My guess is that when you begin to trim so the cavitation plate is beginning to angle up, it is doing two things. Most importantly, it is pushing the water up, and leaving a low pressure area between the prop and the cavitation plate. This is allowing the prop to suck in air. Second, it is driving the back end down, which in turn really lifts the bow. Typically, I have seen setups where the cavitation plate is no longer touching the water by roughly 20 mph +/-. For low speeds, the motor is trimmed all the way down, so the water hits the bottom of the cavitation plate, and helps lift the back end, keeping the boat flatter. Once the boat is fully supported by faster moving water on the hull only, the cavitation plate does nothing good. As far as your question about bringing the prop closer to the water, the answer is "probably not". Race boats run with the waterline about even with the prop shaft centerline. One blade out of the water completely. Cavitation is usually not from sucking in air from above the water, but from a pressure change in the water that cause air to come out of it.

    Not guaranteeing this will solve your problem, but I am pretty certain it will.

    See below for a generic reference. Motor height is definitely a personal preference thing. That is why there are height adjustment holes on each motor, and why jack plates are so common. If you have the means to easily adjust height, I would recommend trying a few different heights and see what you like best.


    [​IMG]

    It is also fairly common for people to use a wedge on the 18' dynes to get the motor tucked down further (more down trim basically) to help the boat stay flat coming out of the water and at low speeds. If you don't do anything slower than trick skiing, it may not be that big of a deal for you, but for swivel speed (11-13 mph) it certainly does help. Again, personal preference.

    [​IMG]

    Ponder and play with the many variables. Look out the back when someone else is driving and see what is happening with the motor, wake, table. Ski behind the boat with different setups and drive the boat with different setups. Judging by the work that was put into this restoration, you and your father are not afraid of tinkering to get a final product that you are happy with. Most importantly, have fun!
     
  7. barefootrocker

    barefootrocker Hydrodyner

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    Location:
    Central Wisconsin
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    CWWSST
    You make some good points as far as looking further at the interaction between the cav plate and the water on the prop. I've always thought of it as bringing the cav plate (and prop) above the water was only for go-fast, top speed only, handling be damned kind of boats, but you make a good point about how it affects how the rest of the boat sits in the water and when. And that view of the engine positions, I've read that document a number of times, it's good information! As far as negative trim I think we'll be fine as we'll likely never be pulling more than a couple skiers at a time, but I could be wrong. I would be able to make a wedge like that without too much trouble. It wouldn't be too difficult to move the engine up a hole either, just a matter of breaking the bolts loose and then re-siliconing (or whatever Dad decided to seal it with) the holes. At the end of the day, any changes we will need to weigh the costs and benefits, and how long it would take as well. After all this won't be a primary tow boat, but more a show boat with (very good) skiing functionality. So if we only get it dialed to about 75% optimum that'd be just fine.

    Last time out when we pulled it out of the water, we had a leaking lower unit. Gave us quite a scare but it appears that it was only due to a driveshaft bearing that let go. Dad took the lower unit in for a new bearing and seals. When he got it back though, it appears it still leaked, so we may not get it on the water this weekend after all. :-( Here's hoping, but we'll see. May need to take Malibu instead for the towboat of the weekend.
     
  8. RiverRat

    RiverRat Hydrodyne 18 Specialist

    Joined:
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    508
    Location:
    Shoreview, MN
    Boat Model and Year:
    1971 Baby Dyne
    Ski Team:
    Twin Cities River Rats
    I hope the lower unit issues gets resolved relatively painlessly.

    It is a world of difference when you get the motor height set properly. I would definitely recommend playing with it.
     
  9. jim

    jim Hydrodyne 18 Specialist

    Joined:
    Jun 14, 2006
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    2,321
    Location:
    FL
    Boat Model and Year:
    77 Dyne 18 I/O converted to Outboard
    I vote for raising it to. It worked on my 18. Major difference in the higher speed turns. There is no downside to the wedge, you still have plenty of trim. It really helps with the low speed handling. Mine is raised with a wedge. I use 17 pitch aluminum prop with cup removed for skiing.
     
  10. barefootrocker

    barefootrocker Hydrodyner

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    Dec 1, 2014
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    25
    Location:
    Central Wisconsin
    Ski Team:
    CWWSST
    Latest update for (nearly) the end of the season. Had a couple more hiccups related to the fuel system, but nothing we can't solve. Overall, I'm going to put the stamp on it that the rebuild is complete! I'm sure there will be some purists who won't appreciate the bimini top, but again this is supposed to be a well rounded daily driver.

    IMG_7704.JPG

    Now it's just tweaking. That being said, we've had it out a couple more times, and finally did some pulling with it. Dad still had the 23 pitch on, which pulled fine but made speed holding a little difficult. Even with that, we did some skiing, pulled me, my dad, girlfriend Kerrin, my sister, and the family had a great day!

    IMG_7706.JPG IMG_7708.JPG IMG_7714.JPG IMG_7715.JPG

    A couple weeks later, Dad switched out the prop for a 19 pitch, and that improved driveability greatly. I finally got to barefoot behind the Dyne! The pull from 25 to 42 was like a freight train, this thing is a rocket ship. Sorry for the video quality. It was a pretty busy day, but we saw a quick and calm opening, took it, and at least it's proof of life of doing some footing:



    Hope for many more ski days to come!
     

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