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Need help setting up a 3.5 on a tunnel

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Need help setting up a 3.5 on a tunnel

Old 10-01-2015, 06:03 AM
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wholehog
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Default Need help setting up a 3.5 on a tunnel

Can someone send me some pics of the proper setup for the throttle cable from the servo back to the carb. I am reworking a used Prather with a 3.5 KB. I've not worked on an outboard before but I think I am missing something ie: clamp or bracket and I'm not sure on the proper adjustment of the cable either. Silly me didn't take pic's before tear down and it's been awhile, but the best I can remember, there were a few things amiss with the cable drives for the steering and the throttle. Thanks
Old 10-01-2015, 09:04 PM
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Are you using a pull/pull cable or push rods for steering? LMK & I can get pics tomorrow after work, I have both styles.
Old 10-02-2015, 05:35 AM
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Originally Posted by moparbarn View Post
Are you using a pull/pull cable or push rods for steering? LMK & I can get pics tomorrow after work, I have both styles.
Thanks for the reply. It is a cable system. I think I figured a fix last evening but I would still like to see the pic's. Issue I was having was the throttle cable that wasn't in the tube would bunch up if operated with the motor turned to maximum position.
Old 10-03-2015, 02:12 PM
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ob nut
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I don't have any pics with me. But the basic setup is cable and sheath. The sheath needs to be hard mounted at two places. One on the radio box and second on the motor. O.S. makes a nice motor mount if you can't make one out of brass. Make sure there is enough length to allow proper motor turning movement. There are several ways to connect the cable to the servo and carb arms.
Old 10-04-2015, 02:25 PM
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My 11cc setup. Throttle clamp is K&B



Steering rods and throttle cable out of the radio box. Way too much slack. Waiting on a new custom fuel tank to arrive. After that, will set up the throttle to a more permanent setup.



My 7.5 setup. The throttle clamp is the O.S. version.



Pull-Pull tensioners:



Hanger9 Pull pull wheel - cable being used is coated kevlar cord.



Throttle cable slack to allow for movement.



HTB290 with rods. See the slack in the throttle cable? Easy movement allows no binds.



Radio box view:



Another O.S. cable clamp.


Last edited by ob nut; 10-05-2015 at 04:02 AM. Reason: Better Pics
Old 10-05-2015, 05:55 AM
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Very nice set ups, thanks a bunch. My close by hobby shop closed after thirty five years, been using it for about five, so I'm SOL now for picking up the small things. I took the steering cables off that came with the boat, I think the owner didn't know how they should be. I had some push rod lying around so I changed the set up to push rod. Moved the throttle cable to a more suitable local and bada-bing everything seems to be working very nice. If I can find another shop close by I might go back with the adjustable rod ends like you have demonstrated. Really sucks having limited resources, seems no one around here messes with boats, so they don't have the parts or a clew what you are asking them about. If I didn't have guys like yourself to ask sometimes silly questions, I would be screwed. Again, thanks
Old 10-05-2015, 12:03 PM
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Supporting the LHS is a great thing. However, some LHS's don't care about supporting those not in their core customer base. Thankfully, those are far and few in-between. (I hope) If you still want to buy from them, the trick is to know what you need and just go in buy and walk out. Research what you need by going to online stores, write down mfg name and product number. The LHS should be able to order those for you without hassles. If the LHS supports planes, most of what I have comes from that area. Rods, cables, collars, clevis's and fuel lines are examples. The rubber seals are from Auqacraft, quick disconnect rod ends are Sullivan. The odd items were either online store order or ebay purchases.

Thanks for the comment on my setups. If you want to know more about them, let me know. Always happy to help out a fellow tunnel boater!
Old 10-05-2015, 01:23 PM
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Thanks for the offer, I'll take you up on that if the need arises. Bought my first boat from the store that closed, it was there on consignment and I shopped there from then on out. The guy and one helper was a wealth of info and that in it self was worth the 40 mile drive. He didn't have my e-mail to tell me he was selling out, so the last time I was there was the last day for the store, I was shocked. Any-hoo I have a 32 inch I'll be working on when it get's out of the paint shop, it has a 7.5 KB on it with everything it needed already installed. Like I said, never had an outboard, always thought they were cool. I have 12 hydros (nitro) and one catamaran (electric). As far a s screws,rods, fuel & water line,cables and the such, he always had that in stock. Like you said, most LHS are clueless which Hobby Town is one, there is one of those where this other shop was. I almost told one or their sales people Saturday they needed to walk their store and learn their product and it wasn't just boat stuff. Gota run, if you don't mind, I'll send you some pic's of the finished products. Frantz
Old 10-05-2015, 04:47 PM
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Tunnels are a blast. Only type of boat that I race currently. At one time, I had a Sport 40, just never got back into them after the boat gave out. Nothing wrong with other style of boats, I just have my niche.. As the saying goes, what ever floats your boat!

With that, don't get discouraged if the Prather doesn't run as you like. If you are just going to play with it, have fun. That boat is a 40+ year old design. There are much better "race" boats out today. Post some pics once you have it all together. Only stupid question is the one not asked.....
Old 10-12-2015, 01:29 PM
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Default Finished Tunnel

Originally Posted by ob nut View Post
Tunnels are a blast. Only type of boat that I race currently. At one time, I had a Sport 40, just never got back into them after the boat gave out. Nothing wrong with other style of boats, I just have my niche.. As the saying goes, what ever floats your boat!

With that, don't get discouraged if the Prather doesn't run as you like. If you are just going to play with it, have fun. That boat is a 40+ year old design. There are much better "race" boats out today. Post some pics once you have it all together. Only stupid question is the one not asked.....
Finished Tunnel! I know the ole girl is old but she sure turned out nice, now test and tune. Thanks everyone.
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Old 10-12-2015, 02:22 PM
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Looking nice.. What do you have for a steering servo? Want around 80 oz-in torque, if not more. These old eye's could quite read the numbers. The 148 will work fine for the throttle.
Old 10-13-2015, 06:38 AM
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Does look very nice ��! Looks like a futaba 131 series, 44.5 in./oz. of torque. Like Mark says, 80 in./oz. absolute minimum!! I prefer something over 100 on a 3.5 tunnel. Lower torque will enter a turn OK, but will have trouble straightening back out - if at all......lots of stress & load on o/b steering, metal gears & ball bearings are a requirement for me.

Last edited by moparbarn; 10-13-2015 at 06:40 AM.
Old 10-13-2015, 07:05 AM
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Thanks guy's, I'll check out the servo this evening and change it if need be. I am not crazy about the push rods either, got a set of cables with ball joints coming snail mail this week I hope. This boat is just for fun, don't have any place to race anyway and I will probably e-bay it and keep the 7.5 project, just have to see. By the way, can you tell me where to get the best deal on the servo I need?
Old 10-13-2015, 09:31 AM
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Gizmomotors.com or zippkits.com or technologyhobbies.com are all dedicated boat sites. I deal with all 3, all are great to deal with!! Get a pull-pull wheel to go with your cables, try to match the diameter as closely to the steering arm on the engine as closely as possible. Will make setup easier & much more linear in action. Mismatched widths will cause slack in the non pull side in cables & bind in pushrods, due to the difference in sizes causing a different distance traveled. The different arcs scribed end to end are small, but add up to more than you would think in actual travel. A servo horn moves the rod or cable side to side as it turns in an arc. A cable comes off a wheel at the same place in relation to side to side, much easier on seals if used. With a wheel, no seal is needed, as shown in Mark's pics here & the ones I emailed you. Just a simple tube with a fuel line or heat shrink wiper. The tubes don't rot & leak over time like seals can

Last edited by moparbarn; 10-13-2015 at 09:36 AM.
Old 10-13-2015, 10:14 AM
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Originally Posted by moparbarn View Post
Does look very nice ��! Looks like a futaba 131 series, 44.5 in./oz. of torque. Like Mark says, 80 in./oz. absolute minimum!! I prefer something over 100 on a 3.5 tunnel. Lower torque will enter a turn OK, but will have trouble straightening back out - if at all......lots of stress & load on o/b steering, metal gears & ball bearings are a requirement for me.
Checked the servo at lunch, you sure have good eyes, it is a S131SH. I'll check the sights listed above for the upgrade and go back to look at the pic's on the wheel set up. Thanks again.
Old 10-13-2015, 12:14 PM
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Originally Posted by moparbarn View Post
Gizmomotors.com or zippkits.com or technologyhobbies.com are all dedicated boat sites. I deal with all 3, all are great to deal with!! Get a pull-pull wheel to go with your cables, try to match the diameter as closely to the steering arm on the engine as closely as possible. Will make setup easier & much more linear in action. Mismatched widths will cause slack in the non pull side in cables & bind in pushrods, due to the difference in sizes causing a different distance traveled. The different arcs scribed end to end are small, but add up to more than you would think in actual travel. A servo horn moves the rod or cable side to side as it turns in an arc. A cable comes off a wheel at the same place in relation to side to side, much easier on seals if used. With a wheel, no seal is needed, as shown in Mark's pics here & the ones I emailed you. Just a simple tube with a fuel line or heat shrink wiper. The tubes don't rot & leak over time like seals can
Ok guy's help me out here. Went to some of the sights for the servos and there are a slew of them and I don't have a clue. The ones I think will work are from 12 bucks to 23. Would you mind choosing one for me? Nothing fancy but one that meets the specks you mentioned and I think I would like to stay with the push-rods for simplicity. The width of the steering arm, not for sure, I assume it's the stock KB part.
Old 10-13-2015, 01:59 PM
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In no particular order: Futaba S3305, Savox SC0252MG or Hitec HS645MG. The Savox & Futaba share the same spline, Hitec is different. If staying with pushrods, use a heavy duty or aluminum servo horn with the same (or as close as possible) width as the steering arm on the engine. Radio box width may not allow that, though. If the box won't allow that, get as close/wide as you can.
Old 10-13-2015, 02:42 PM
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If at all possible, I run the Futaba 3305 MG for my steering on 3.5 boats. Hanger9 Pull-Pull wheels are Futaba or JR servos. They don't fit HiTech's. However, Aquacraft has a pull-pull wheel that can be mounted on any round servo arm. I have two boats setup with this style of steering. As Mopar stated, there's no slack or binding with this setup. I plan on using this with any future builds.
Old 10-14-2015, 05:40 AM
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You guys are great, thanks so much for the help.
Old 11-02-2015, 08:49 AM
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Originally Posted by ob nut View Post
Looking nice.. What do you have for a steering servo? Want around 80 oz-in torque, if not more. These old eye's could quite read the numbers. The 148 will work fine for the throttle.


Pulled a servo from another boat that had the specks you recommended. Built a bridge in the radio box so I could install the servo so the arm was cross way instead of as before. Still had an issue with the rods dragging on the canopy because of the wide spread on the motor control arm. Drilled some holes in the arm to bring the rods in just a tad and that did the trick. Seems this setup works good. Look forward to spring time again to find out. Hopefully the paint shop will get off their butts and get the 32IN finished.
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Old 11-02-2015, 06:32 PM
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Looking good. And what do ya mean "Look forward to spring"? I was out last Thursday, a nice cool 55! Plan on going out this coming Thursday, should be low 70's. Love telling this story. Decades back when I first started to run boats, my buddy and I went out 2nd week in December. Took off the water cooling tubes / hoses from our K&B's. Since it was snowing out, didn't think the motors needed much "water cooling" to not over heat. We went back the following week to only be disappointed. The local kids were playing hockey. If the water is still liquid, it's running time!

Last edited by ob nut; 11-02-2015 at 10:06 PM. Reason: spell check
Old 11-02-2015, 09:17 PM
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I have to agree with Mark, if you have water you can "legally" run on, as they say in the Nike commercials JUST DO IT!!!!!!!!!!!!!!!!!!!!! No need to wait for spring. Just be sure you have some way to retrieve the boat if it dies
Old 11-03-2015, 07:28 AM
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Originally Posted by ob nut View Post
Looking good. And what do ya mean "Look forward to spring"? I was out last Thursday, a nice cool 55! Plan on going out this coming Thursday, should be low 70's. Love telling this story. Decades back when I first started to run boats, my buddy and I went out 2nd week in December. Took off the water cooling tubes / hoses from our K&B's. Since it was snowing out, didn't think the motors needed much "water cooling" to not over heat. We went back the following week to only be disappointed. The local kids were playing hockey. If the water is still liquid, it's running time!
I'm with you guys on that. Problem Is the city closes off the park where I go to start putting up decorations for the drive through light show. Water at the home pond is too low and without walking in a foot of mud to get the boat tossed to the water, well that ain't happening. The other point that was mentioned was retrieval, brrrrrr, not swimming in cold water, hey, I don't even like cold weather.
Old 11-03-2015, 05:12 PM
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Originally Posted by wholehog View Post
I'm with you guys on that. Problem Is the city closes off the park where I go to start putting up decorations for the drive through light show. Water at the home pond is too low and without walking in a foot of mud to get the boat tossed to the water, well that ain't happening. The other point that was mentioned was retrieval, brrrrrr, not swimming in cold water, hey, I don't even like cold weather.
Points taken and understood. Guess growing up in Michigan, when it actually snowed from Nov - Mar, cold was the norm for this time of year. Lucky for me our club has a pond that is all ours and two retriver boats for use.
Old 11-12-2015, 08:57 PM
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Originally Posted by wholehog View Post
Finished Tunnel! I know the ole girl is old but she sure turned out nice, now test and tune. Thanks everyone.
Whats with the stripe paint job on the bottom?

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