Thread: 12ft Tunnel Build

  1. #221
    BoatRacingFacts VIP John Schubert T*A*R*T's Avatar
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    We are talking about 2 different things. First, you need to align the ends of the steering bar with the swivel pin not tilt pin. The swivel pin is the vertical pin that attaches the drive shaft housing that swivels left & right (for steering) to the swivel bracket. The tilt pin is what attaches the right & left side clamps to the swivel bracket to accommodate allowing tilting out & under, & BTW with cables tight it will still permit trimming "in" & "out". If the steering cable ends are not in line with the swivel pin, as they aren't now on your set up, the steering will not work correctly. Will lock up one way & loosen the other.

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    Team Member zul8tr's Avatar
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    [QUOTE=ice_spy;146112]Zul8tr it's a standard tohatsu MD50 gearbox 1.85:1 The cowl and bed pan has been swapped with a 40hp merc for damage reasons, the Hillmarine signature race clever is an 18p to begin with, not intended to provide maximum speeds yet.
    Stickers are for show, from some of the products and companies I use, some I've just collected over the years. They also do a good job of covering up paint defects and runs
    I'm expecting speeds over 60mph to begin with.

    For speed at 60 with that pitch and gear ratio you need to turn about 7000 rpm with 7 % slip (zero slip not possible) at the prop, definitely doable speed. I suppose you will run over 7000? Not familiar what that Merc will rev to.
    John is right where the steering bar end holes need to be relative to the engine left - right pivot.
    " Three may keep a secret if two of them are dead" Ben Franklin

    Location: SW Orlando, Fl

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    Team Member ice_spy's Avatar
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    Ok, now I understand what you are saying. I didn't pick up on the swivel tube term sorry , i misinterpreted for the tilt tube. I was under the impression it had to be aligned with the tilt tube so that when tilted up or down tension does not change due to an arc if it were not in line with the tube. I see what you are saying, It makes sense that the steering pivot point is the swivel tube. And then where I must of been mislead, is the bar end hieght is meant to be the same as the tilt tube in line with hieght not in line horizontal across the boat ?
    Feeling a bit confused. At least I can simply cut some off the bar ends if needed. Appreciate you picking up on that thanks John.

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    Team Member ice_spy's Avatar
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    Ok, so the plans have misled me to believe I needed to place in line with the tilt tube, also from a small 9 ft hydro I had it was in line with the swival tube but tension on tilting was affected. I see this set up allows pivot from the swival tube and keep tension at the tilt tube with this extra extension on the bar ends before the pulleys.
    The race never stops

  5. #225
    Team Member Chairman's Avatar
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    I disagree with the above opinions, and say that you have set it up correctly -- aligned with the TILT pivot point. Otherwise, your will cables will either tighten or loosen as you run your trim, and the differences in cable tension can be considerable. If you set your cable tension with the motor trimmed all the way down, the cables will tighten as you trim up, possibly to the point where something is liable to break.

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  6. #226
    BoatRacingFacts VIP John Schubert T*A*R*T's Avatar
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    Not true Chairman, they must be aligned in a line that the ends of the steering bar are even with the swivel pin, it's physics. I've rigged so many boats I can remember the number. If not aligned the cables can tighten or loosen when steering. Now the issue of trimming & the cables, sure they will tighten some when trimmed down & loosen some when trimmed up, but shouldn't break the cables. We never did when I drove for OMC.

  7. #227
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    I always set mine to the (tilt tube) that is the only fixed point that does not move. If the end of your steering bar or center of pulley are inline height & length to center of the tilt tube. you will be good. Cable still will tighten slightly from full trim out to full trim in. That is due to the pulley extending the cable back. For this I always trim the motor all the way out and tighten the cable. The cable gets a little (very little) tighter as you trim in. Don't know if this is the best way just the way I do it. I have enjoyed this thread.

  8. #228
    Team Member ice_spy's Avatar
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    It's great to see different opinions. It sounds like a case of what works for some may not work for others.
    I would like to say that I think both positions is correct with the use of the extended bars pivotal on the bar ends as shown on the efi merc pic I posted previous.
    I agree with both answers and this is from what I can see the best and only way to set it up 100% correct.
    As mentioned the pivot point for the steering must be in line with the bar ends, if it is not in alignment with the swival tube you will have a tight one side loose the other, cables which creates binding as said and as I have experienced too. It must be aligned here. However this does not allow for correct tensions on the cables when trim and tilt is operated. Therefor to allow a good range of tilt and trim without loose and tight cables operating in an arc movement the pulleys need to be in line with the tilt tube.
    Utilizing the pivotal extensions on the bar ends not only brings the bar end pulleys forward in alignment with the tilt tube it also allows the cables to run closer to the fuselage without hitting while maintaining a straighter operation of the cables. Positioning of the tie backs along the sides of the fuselage will also play a vital part in the set up, allowing a tangle free movement of the two cables and a straightforward pull close to 180 around the pulley. This will yield best results for lighter steering, not forgetting maybe the most important feature is the closer to the motor the faster and less turns on the steering wheel, whilst bars out further will have a slower with more turns needed on the steering. Again this shows the use of these extended pivotal bars keeps the steering in tight for quicker turns with less wheel throw. The only part I need to work out now is how much degrees of steering will be needed/wanted

    Zul8tr the motor is a MD50HP early model TOHATSU with the swirl head and the larger exhaust tube. Not a Merc 40hp. And no I will not be revving beyond 7000pm even with a welded crank. 6800 would be more endurance for the motor but dam ! 7000+ rpm sure would sound nice !
    Getting close fellas. My bar end pulleys, coaming pulleys and tie backs arrived today Looks like I'm a lenght of cable away from having the boat rigged and ready for a test run.
    The race never stops

  9. #229
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    As far as steering I always go lock to lock. You will need it on a tight ramp on exit to get the nose around.

  10. #230
    Team Member ice_spy's Avatar
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    I agree Dave, full lock would be an advantage whilst maneuvering at slow speeds and returning to trailer / dock etc. Power trim and tilt on the other hand would not require fully tilted up postion imo as the motor does not need to be in the tilt up postion for trailering and would probly only require the most amount of tilt when launching and retrieving the boat. I can limit this amount of travel with a micro switch if needed.
    I still have to make a gear select lever for the cockpit and will add a trim Guage wire and large display above the tacho. As much as i want to test out the boat asap, I still need to get these last few thing's sorted and set up first. The seat needs to be mounted on some blocks Also. It would be nice to have adjustable tilt and slide on the seat, but I'll just have to play around with postion and see what feels best. Will get this outrigger steering finished off today and post up some pics of the set up. I noticed many tunnel hull boats have the extension built into the bar end pulleys which brings it in line with the tilt tube but allows pivot point from the swival bracket.

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