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Old 23 July 2019, 22:21   #1
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Tohatsu 15 hp throttle doesn't spring back

I recently purchased what appears to be an excellent condition 2000 Tohatsu 15 hp 2-stroke outboard. The only thing that concerns me about it is the throttle doesn't "spring" back to idle when you release it, like I'm used to with other motors I've used. I'm not certain if this is just the way Tohatsu designed this era of motors, or whether a spring is missing. Take a look at the throttle linkage I took some photos of:


https://drive.google.com/open?id=1JK...4pcGuSeWwkKOtk


That hole that I've circled appears to me like it could be where a spring should be located to bring the throttle back to idle when released. Indeed, if there was a spring there, I think it would do just that (seems it would have to be pretty strong). If so, I just can't see where the other end of it was meant to be connected.



So is my motor missing a part or is this just the way it was designed?
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Old 24 July 2019, 00:31   #2
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You can see the entire parts list for your model here: https://www.tohatsuoutboardparts.com/Parts-Books.html
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Old 24 July 2019, 02:23   #3
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Sounds like a problem I recently fixed with my Johnson 4hp. Throttle cable didnít spring back because the timing plate under the flywheel. Normally it should spring back when you release the throttle by a spring on the timing belt. If you type in the search Johnson 4hp you can find my post with photos
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Old 24 July 2019, 02:24   #4
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Should have said - because the timing plate was seized with old grease
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Old 24 July 2019, 04:30   #5
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I assume this Tohatsu has the usual throttle friction adjustment somewhere on the tiller? Not that too tight is it?

Another idea for a problem is the one I had on my very clean Yamaha 15 nearly the same age...

The throttle was quite stiff to return to idle despite the tensioner being loose and linkages oiled. Took the twistgrip off and dry grease plus light alloy corrosion dust were the culprits.

Looking at that parts pdf Poly linked seems yours has a similar arrangement that one screw to remove and the twistgrip will pull off. Screw 22 on page 19 of the pdf.
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Old 24 July 2019, 08:16   #6
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Thanks, everyone. I'll dig a little deeper and look over that parts list closely. I do notice a bit of a mystery already, however. That parts list seems to indicate Tohatsu didn't make a 2-stroke 15 hp motor in 2000. But the emissions tag clearly notes a manufacture year of 2000 and my Tohatsu manual says it's a 2-stroke and requires a 50:1 fuel mixture. Maybe the parts list is missing models or maybe my understanding of 2-stroke and 4-stroke engines is wrong?
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Old 24 July 2019, 09:52   #7
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Those images are of a 2-stroke for sure so that's what you have. The bottom hole on that lever you circled is for attaching the throttle linkage when it's on remotes.

BTW that Tohatsu looks mint.
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Old 24 July 2019, 10:01   #8
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Yeah, it’s a beauty and purrs like a kitten. Seller said he only has about 20 hours on it.

The more I look at the schematics and parts, the more I’m convinced this was never designed with a spring loaded “return to idle” on the tiller. Probably not wise to try to jury rig one. Just seems inherently unsafe to me, especially considering the throttle actually has a sort of soft “lock” position at the highest speed. But I guess if the kill switch and lanyard are being used (and work) properly, they figured a spring loaded tiller handle wasn’t necessary.
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Old 24 July 2019, 13:48   #9
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No 2 strokes Tohatsu 9.9-15-18-25-30-40 HP throttle grip will return fully to idle position when the throttle was released from whichever throttle position the motor was working at. it's the nature of those beasts, were engineered to work that way, no spring or part is missing...

The rod throttle system is very basic and simple compared to other models or motor brands. If wanting the throttle grip to fully go back to idle when released, all the sliding, rotating parts must be fully greased for the system to achieve the least restriction whatsoever, can add a spring to the circled hole located on the throttle arm and secure other side against something to hold to.

Tohatsu still manufactures and exports 2 strokes 2.5 to 115 HP motors for the rest of the world that has not banned 2 strokes motors...

Happy Boating
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Old 25 July 2019, 10:02   #10
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Spring Installation.-

Update :

Have not installed a spring myself to fully back the throttle grip to min idle position as I'm used to back it with my hand since day one. If wanting to install a return spring on any 9.9-15-18 HP Tohatsu motor this is an excellent place to do so. Check pic.

Release the entire load on the tiller grip. Install a medium load SS spring between the eye of the arm plate and the big nut which is the exhaust flushing port. Solder a small eyelet on top nut to hold the extreme end of the spring.

Before removing the nut, mark the eyelet at a proper working position before welding it. Once done, apply a coat of grease on the nut's threads before screwing it back in to be able to remove it anytime if wanting to flush the motor using a flushing adapter.

Don't forget to grease all sliding and rotating elements to help the spring do its homework right...

Happy Boating
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Old 25 July 2019, 10:18   #11
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Thanks, that's awesome advice! I think I'll play around with it a bit on the water to see how big of an issue/concern I think it's going to be. Maybe it's not as big of a deal as I think it is. I've read in other threads and forums about how it can be a pain to have a spring loaded throttle, especially if on long trips.
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Old 25 July 2019, 11:46   #12
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You're welcome, holding a throttle grip that automatically springs back to min idle will surely tire your hand on long cruising outings at faster speeds compared to the simple standard factory delivered mechanism.

Happy Boating
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