12' Olympian To Fill Some Voids

Discussion in 'Watercraft' started by LCnSac, Mar 17, 2012.

  1. LCnSac

    LCnSac John or "LC"

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    I have never used a jack plate, and although I could be wrong I don't think they help much if at all at low speeds, which is where I'd be going up a skinny river. I wouldn't put one on this boat regardless due to transom stress, and I don't have that high a confidence level about the boat's structure.

    The prop cage seems to work well, but I think it creates some drag. I am going to remove it and drop on a hydrofoil instead for lakes; those always seem to help on smaller boats. I have a tiller extender, but it's more for convenience than weight distribution. The boat pops right up with me in the stern or with two people on the boat. My Yami has a shift control separate from the tiller. I really do like that feature of having the two together, but it is what it is and the motor is quiet and strong. Not sure if this is a Yamazuki or Yami pure bred but it's helluva lot quieter than the Mercs and it's built in Japan which is a luxury today.
     
  2. mbowers

    mbowers Active Member

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    [​IMG]
    Looking at that picture the motor just looks set really low which is why I thought the jackplate could help. The jackplate won't improve fuel efficiency much at low speed but it does directly reduce your draft at low speed which I think would be very useful going up a skinny river. It also helps with getting on plane. I was looking at a hydrofoil or a jackplate and decided to try the jackplate because it meant holes in the boat and not in my motor. The jackplate helped my planing issues and then you get the bonus reduced draft and increased cockpit space by moving the engine up and back. Too bad the transom strength is such a worry. :(

    I bet that prop guard creates a lot of drag! :) Looks good for driving all over your downrigger line with no problems which probably happens a lot with downriggers mounted so far forward from the stern. :)
     
  3. LCnSac

    LCnSac John or "LC"

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    The cavitation plate is about 1/2" below the hull, although the picture makes it looks a lot lower. I'm going to put on the Doelfin today and test it.

    Glad you mentioned the down rigger amidships because few people are less experienced with down riggers than I. The first time I used a set of clamp on portables I neglected to tighten one clamp before I dropped the weight. Now I have one portable :). I will watch out for the lines. I took them off last night--trying the make the gunnels fly line friendly. They won't get much use except in the summer in high lakes, and maybe for some salmon. Not really my style of fishing. I thought about selling them but nah.
     
  4. psycho

    psycho Active Member

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    The downriggers should be back around where that red strap is in your first picture. Mine are a little forward of that but mine have sixty inch arms. But then I have side planers mounted near the bow too.:D
     
  5. mbowers

    mbowers Active Member

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    How's she fly without her mouthguard?? :)

    I think the anti-ventilation plate should be about at the water's surface when planing which I'm guessing is probably 3-4" above the bottom of the hull.

    One more trick for performance IMHO: use non ethanol fuel if you're not already. I think I get the expected 10% more HP by getting rid of the ethanol and the motor is definitely easier to start. You should also get 10% more range from a tank by getting rid of ethanol. Even if the non ethanol costs a lot more, fuel costs are so small with a 15 HP you probably won't notice the price difference.
     
  6. LCnSac

    LCnSac John or "LC"

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    We'll find out when the rain lets up. The Doelfin is on and ready, but that galv prop guard will be used for the low rivers. I am using the crappy weather as time to do some mods and maintenance. Fabbed a bow stop for the trailer which never had one--why? The boat is stripped of flyline grabbers, down riggers, and graphics. No one ever installed rear deck cleats (why?) so those are done, slightly below the gunnels. A few holes above the waterline filled, and the cad plated screws (???) for the transom motor plate replaced with stainless. Good opportunity to poke around in the transom and it's dry and rock solid. 5200 is my friend--as is acetone to clean up my occasional whoops.

    If non-ethanol gas is available in California, I don't know about it. Our standard blend is 5.8%E so for a small motor I'm not going to worry about it.
     
  7. mbowers

    mbowers Active Member

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    Looks like there's a couple but not many. http://pure-gas.org/index.jsp?stateprov=CA The nice thing about getting non ethanol for a small motor is you can fill up a couple of 5 gallon jugs and be good for the season if the nearest station is far away. In FL I make sure I've got 8 jugs filled anyway before hurricane season because gas can be out for a week or more after one of those and then just use it up in the boat over the winter..

    Did you put in pop cleats at the back or just regular fly line grabbers? :)
     
  8. Jim Wallace

    Jim Wallace Smells like low tide.

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    I am finding this discussion to be of interest. don't mean to hijack this thread, but mbowers' mention of the position of the cavitation plate in relation to the bottom of the hull, and that it affects performance, perked up my ears.
    My 16'er is underpowered with the 9.9 Bigfoot, and I can live with that for now. I notice that the cavitation plate on my 9.9 lines up a good inch or so lower than the bottom of my stern. That is why I was thinking of a jack plate. My stern has a fairly steep angle to it, so I don't really need the setback. What I think I need, is to just raise my transom about an inch (or maybe 1.5"), and then get something like a Doelfin.
    None of my local friends, or anyone I know, confess to being experts on the proper positioning of an outboard motor or tweaking the mount for performance, so, I figured that the manufacturers might have their stuff together and everything should fit just right, "out of the box" (Ha!), and just clamped the motor to the transom, drilled a couple of holes, and bolted it on. I also have a lock over the clamps, to help keep the motor from falling off when the boat's on the trailer and I'm not watching it.
    I'm rethinking this whole arrangement and wondering if I can get better performance by tweaking it a bit. I just don't know what I'm doing or where to start.

    I'm lucky to have a nearby gas station that sells non-ethanol gas. I won't run ethanol gas in any of my small gas engines.
     
  9. LCnSac

    LCnSac John or "LC"

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    What you do, Jim, before spending any money on jack plates which probably won't do much for a 9.9 anyway is get some aluminum shims at Depot and start applying shims between the motor and transom. Using a GPS if you have one, do some speed trials including pitch. You will probably find a sweet spot pretty close to where you are now. A Doelfin will probably help too.
     
  10. Jim Wallace

    Jim Wallace Smells like low tide.

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    Thanks for the advice, LCnSac. Messing around with shims and testing...OK, I'm good with attempting that. Once I figure it out, I won't have to wonder.
    I found a nice piece of Spruce that is the exact same thickness as my transom. I can sandwich that between two aluminum plates as a bolt-on extension, once I determine whether or not I have to raise the height. I have 3 pitch settings, and the middle one seems to work best right now.
    I have a new sonar/gps unit that I haven't even tried out yet, so I finally will be able to determine speed.

    My plan is to remove my thru-transom bolts, and then head to a lake and test it, adding shims to raise the motor's height until the performance peaks. Then check the pitch again. Sounds easy enough, anyway, as long as I don't drop my wrench in the lake.
     
  11. LCnSac

    LCnSac John or "LC"

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    You can actually use what you have permanently Jim. Maybe epoxy the spruce but it's a light setup and you don't need to do much more than use shims. You can also play with prop pitch but for a small motor it's probably not worth the expense and effort. i have a stainless 3 blade on mine, as a result of the aluminum prop being chewed up. That's exactly why I don't like stainless props--it's a helluva lot cheaper to replace a prop than a drive shaft (I speak from experience on the Whaler) and I will probably get a new aluminum prop and sell the stainless.
     
  12. Jim Wallace

    Jim Wallace Smells like low tide.

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    Thanks again for the advice, LCnSac. My 4 blade aluminum prop is in great shape. Only once did I slightly polish the leading edges of the blades in the mud by not paying attention, when going over the shallow mudflats. Was only the 2nd time I had it back in that shallow estuary (usually just paddle my yak back in there), and I strayed a bit from the main river channel. I quickly corrected and steered away from the shallows. Was lucky not to hit any woody debris. I now pay better attention.
     
  13. mbowers

    mbowers Active Member

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    One of the key pieces of info to get the correct size prop involves using a tach to get the motor RPM. Using the GPS speed is probably good enough though. Adjusting transom height with shims etc is a great idea to get a feel for what's optimal. I wouldn't be surprised if it's 2-4" though. I was instructed to start with pitch / trim at the lowest hole and keep raising the transom until you lose performance. I still feel the jackplate is a much more secure way to increase the height of the motor than anything you bolt on the top of the existing transom. The setback should let you raise the motor even further as the water height behind the boat rises with distance back from the transom. The jack plate is only $85 for a solid piece of cast aluminum that's manually adjustable to the 1/2". It will be tough to rig something up that's not adjustable, half as strong and twice the price IMHO.

    I want to try a mini jacker out on another small boat this summer and I'm so sure you'll like it on your boat Jim that if you buy one for your boat and don't like it before I'm going to buy a new one (say mid June), sell it to me and I'll pay the full $85 plus sales tax and $10 for shipping (it's probably $20 for shipping from WA to FL) so your only risk (besides your time and a couple holes in the transom :) )is driving to the store and $10 for shipping.
     
  14. Jim Wallace

    Jim Wallace Smells like low tide.

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    Thanks for the additional advice and offer, mbowers. I'm hoping to get the boat in the water sometime this Spring, and get it worked out. I just finished some modifications on my yaks, and I need to go paddle.
    Don't wait for me to get a jackplate, whatever you do. Just order one!
    Although I usually paddle my U-12 when I fish lakes alone, I might start taking the tinny.
     
  15. BFK

    BFK Member

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    I wonder how much improvement you will get with a lot of tweaking. The Bigfoot is designed to provide a lot of low-end torque as a kicker for big boats. It's not really intended to be the fastest motor in its class. Raising it up to reduce lower-unit drag will help some as will a prop change, but if you can plane your 16, that is probably about all you can realistically hope for, IMO. As I recall, it's gearing that is your root problem--although the big prop isn't helping.