# Tohatsu Problem



## Ruger (Feb 20, 2018)

I have a 2020 Tohatsu MFS 60 with about 13 hours on it. Starts fine, initially goes into F and R with no problems. When slowing down from a 20 minute cruise, the IDLE detent is no longer there. The shifter just moves back and forth. But, the engine will go to IDLE and then begin revving up all by itself, I have to shut it down just to keep it from over speeding. When I restart the engine it begins revving up by itself again until I move it into gear, unpleasant sound. Now the boat won't go into Reverse at all. Kind of frustrating, any ideas?


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## devrep (Feb 22, 2009)

warranty service?


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## Frank Ucci (Jan 20, 2019)

Shift cable/linkage. Who rigged it?


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## Ruger (Feb 20, 2018)

It was the lower unit. Under warranty.


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## mwolaver (Feb 6, 2014)

Please update us on your warranty experience. Have heard some lengthy horror stories and hoping they are isolated. thanks.


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## Ruger (Feb 20, 2018)

Tohatsu warrantied the lower unit. I guess it was a spontaneous failure. It only has 12-14 hours on it. I haven't hit anything. The folks that fixed it said the prop hub was slightly out of round which may have caused the lower unit to fail. The prop people said there's nothing wrong with the prop. I put a stock aluminum one back on. I'll run it later this week and see how it performs. ‍♂


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## jay.bush1434 (Dec 27, 2014)

Tohatsu may have had a bad run of lower units or at least some of the internal parts. A good friend of mine sheared a prop shaft on his Tohatsu 50 with about 30 hours on it. Just running across the bay and suddenly the engine revs way up and boat slows down. No impact on anything. Was covered under warranty.


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## sjrobin (Jul 13, 2015)

Heavy cupped large diameter props put a lot more stress on the prop shaft and drive train. Hitting sand bars occasionally might also. In my long experience with various outboards except 4S Tohatsu, the prop usually suffers the damage by spinning the rubber hub or at the most bending the prop shaft. I believe quite a few 4S Tohatsu prop shafts have failed in Texas after hitting the sand or oyster, not just spinning thru H2O.


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## Ruger (Feb 20, 2018)

Good info. I'm going to leave the aftermarket prop off. If by chance it did cause the failure I don't think Tohatsu would warranty the lower unit again, and it was a 1600.00 repair.


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## lemaymiami (Feb 9, 2007)

Something for everyone to remember about props... Originally most outboards came with aluminum props (slang years ago... we called them "sand props"). Not as efficient as the later stainless steel props... those old aluminum props were a lot softer and that meant that the prop took a beating and absorbed a good bit of it - lessening the impact on that lower unit's gear train... Along comes stainless and everyone switches to it if possible since it's more efficient, quicker, etc. The only downside to a stainless steel prop is that it's much harder than aluminum -so if you hit something - much more of the impact is transmitted to your drive train - occasionally with very bad results for those gears and shafts...

Just something to keep in mind. Some of us run in very forgiving waters where the bottom is pretty soft - sand or mud... So if you run aground the consequences are relatively minor. For anyone running in hard bottomed areas that nice fast stainless prop might end up contributing to a lower unit failure after a grounding or two...

Of course all bets are off if you hit a submerged tree or big rock (another of those "ask me how I know" moments) at this end..


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## Ruger (Feb 20, 2018)

Well, got it out of the shop with a new lower unit. I put a stock aluminum prop on and it ran fine for a 20 minutes and now it's doing the same damn thing.


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## sjrobin (Jul 13, 2015)

Not many of us will publish problems with equipment we have purchased. I for one appreciate your honesty.


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## scissorhands (Apr 8, 2012)

When you say idle detent, are you referring to the variable idle?


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## Ruger (Feb 20, 2018)

What do you mean? I’m referring to the shifter in the traditional 12 o’clock position for neutral.


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## lemaymiami (Feb 9, 2007)

The very first question I'd have is.... what make shift/throttle are you using? Is it a Tohatsu or some after market brand? One of the best master techs I ever knew was fond of pointing out that if you strayed from what the manufacturer recommended for a given motor you were asking for trouble. The second thing he'd have pointed out is that if your shifter isn't properly engaging the gears either in forward or reverse then you were in real danger of screwing up your lower unit since the gears need to mesh completely to do their job and have a long life... 

Sounds to me like you're in real need of some factory support... Hope you're able to sort this out - and I would not run that motor at all until it is... Let us know what happens.


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## TravHale (May 17, 2019)

This is the engine I've picked out for my skiff, so i'll be anxiously watching this thread. Hope you get it sorted out soon.


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## Sublime (Oct 9, 2015)

Yeah I don't see how it had anything to do with the lower unit. As far as I know, even none of today's whiz-bang motors have lower units that communicate with the motor's brain. it sounds like some kind of linkage and/or sensor issue. Of course ,as mentioned earlier, if the gears aren't fully engaged that could cause some issues in the lower unit, but the surging rpms would say to me it is some kind of sensor issue.


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## LowHydrogen (Dec 31, 2015)

Dang man, well at least they won't be able to blame a prop hub this go-around. 

Is this a linkage setup or one of the newer fly-by-wire shift/throttle?

If fly-by-wire it sounds like it's probably sensor/solenoid/limit switch etc issues between shift and throttle not communicating properly to me.


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## Ruger (Feb 20, 2018)

It's a traditional linkage set up.


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## Frank Ucci (Jan 20, 2019)

Remove the engine cowling and see if the throttle and shift cable are attached securely and that the cable covers are properly secured at the point that they enter the engine. If those cables are attached securely in both places, I'd say you've got something going on in your shift box. Also, can you tell me who rigged this engine?


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## sjrobin (Jul 13, 2015)

Tiller or remote and where did you buy the engine and who connected the new lower unit to the engine controls?


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## 8w8n8 (Sep 30, 2017)

Ruger said:


> Well, got it out of the shop with a new lower unit. I put a stock aluminum prop on and it ran fine for a 20 minutes and now it's doing the same damn thing.


It appears the dealer did the FCO of the new lower-unit in the shop tank and not on the DYNO! And_ in_ the shop tank for only 10-15 minutes!


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## LowHydrogen (Dec 31, 2015)

Ruger said:


> It's a traditional linkage set up.


This is a strange one. I hope you get it sorted soon.


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## Ruger (Feb 20, 2018)

The issue was a throttle body and ISC valve. The mechanic replaced all associated parts. Those were covered under warranty and now it runs like it should. If your Tohatsu is doing this and the shop can't figure out why - this might be your problem.


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## Smackdaddy53 (Dec 31, 2012)

sjrobin said:


> Heavy cupped large diameter props put a lot more stress on the prop shaft and drive train. Hitting sand bars occasionally might also. In my long experience with various outboards except 4S Tohatsu, the prop usually suffers the damage by spinning the rubber hub or at the most bending the prop shaft. I believe quite a few 4S Tohatsu prop shafts have failed in Texas after hitting the sand or oyster, not just spinning thru H2O.


Sounds like a weak part no matter how big or cupped the prop is. I beat the hell out of my 70TLRZ with a 14” XXXcup prop and not a single issue yet. Tom Horby had several issues with his ‘Hatsu 50 as well. They don’t make em like they used to.


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