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  1. #1

    Default Tohatsu 3.5hp 4-stroke shifting problem

    Hello,

    My wife and I just returned to our boat after a 5 week visit to the US. Our Tohatsu 3.5 hp 4-stroke was on the aft rail the entire time after having been used in fresh water for several months. I mounted it on the dinghy and found the shifter to be frozen in neutral. After messing with it some, I was finally able to get it into gear and back into neutral, but it's really, really stiff - I'm hoping it will loosen up w/ use, but am also concerned something might break if it doesn't. Before we left it shifted effortlessly so whatever happened it's due to lack of use.

    Can anyone tell me why this might happen, where the problem likely is, and how to go about fixing it?

    Mark Kaynor
    s/v "Rachel"

  2. #2
    Join Date
    Mar 2010
    Location
    Buffalo, NY, USA
    Posts
    2,080

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Is the motor running when shifting? It needs to be running to ensure the clutch dog can engage. Other possible problem would be the area where the shifter handle passes into the housing itself. Seldom a problem there, but if some corrosion accumulated, could cause binnding.
    Paul
    Buffalo NY USA

  3. #3

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Yes, engine is running. I'll hose down the shaft where it attaches to the shift lever w/ PB Blaster and see if that helps.

    Thanks for your input,

    Mark

  4. #4

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Wow. That didn't work so well. It seems the PB Blaster lubricated the shift lever on the shaft a lot better than it lubricated the shaft in the housing. Luckily I was able to get the engine in forward so I can at least start it in gear and use it. Dang. And I just got it running good for the first time in months.

    Unfortunately, this is just the latest in a long litany of failures and frustrations I've had with with this outboard since I purchased it new in 2006. I'm pretty disappointed with it and have about given up on it.

    Mark

  5. #5
    Join Date
    Mar 2010
    Location
    Buffalo, NY, USA
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    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    The shift lever is cast onto the shaft. You need a new lever. Apparently the PB blaster was not effective at all, and you have stripped the handle from the shaft. If the shaft is seizing in the housing, you will want to get the motor to a dealer, unless you are comfortable pulling the powerhead to change the shift lever. Likewise, if there is cam rod drag in the LU itself, that would indicate a trip to the dealer. Is there lube in the LU?

    What problems have you had? These are pretty decent, reliable motors (in general), and very simple. I have seen them survive extreme levels of abuse and come up running. Most problems are readily rectified.
    Paul
    Buffalo NY USA

  6. #6

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Paul,

    Thanks for your help. This list has been a great resource for me and I appreciate the time and effort you and folks like you put into it.

    Unfortunately, I'm in Guatemala - no dealer, no parts. I'm going to leave it in forward and forget about it for now - at least it's working. Seems to me that a marine outboard ought not to have corrosion problems like this, but that's just my opinion. The lower unit does have oil - new about 3 weeks before we left. I'll check it for water. I have a new impellor kit, so I'll probably break it down pretty soon to R&R the impellor - maybe something will jump out at me then.

    Other issues - the high points:

    1) Rubber seal between cowling and engine - it shrinks over time I assume due to heating / cooling, and since it's glued to the inside of the cowling, it's difficult to get it reattached and get a good seal. I finally gave up and used some screws and big plastic "washers" on the inside - works fine now. Non-critical, but annoying nonetheless.

    2) Stalling in rough water - runs great in flat water (when it's easy to row) and stalls in rough water (when it isn't as easy to row). Added tilt to the engine and it got marginally better. Added more and that may have improved it a bit more, but it still does it. I make a point of keeping the tank full and that seems to have helped some, too. All that being said, it's a lot better than it used to be, and if this was the only problem, I could live with it.

    3) Drain screw in the bottom of the float chamber - it's frozen in place. I've never had a problem with a jet or drain plug on a carb before - I suppose I may have overtightened it, but I'm usually really careful about stuff like that. Seems like that happened after not exercising the screw for a few months. A new float bowl and screw will solve that one for me. Until then, I just pull the carb every time I need to drain the bowl.

    4) Fuel issues - the majority of problems I've had with the engine have been fuel related. It takes a lot less to plug the tiny orifices in a small 4-stroke than it does a small 2-stroke. Clean, quality fuel can be difficult to find, and as a result, I've had to really improve my refueling regimen. The best thing I did to date was insert a small inline fuel filter w/ a replaceable element. The engine will still run badly or cut out altogether at random times, but it runs for longer and much more reliably than before I installed the fuel filter. My next outboard will have an external fuel tank so I can insert a water seperating fuel filter inline between the tank and the engine.

    5) Ignitor - the ignitor failed while I was at anchor in Miami. Luckily the engine still had acouple of weeks of warranty left on it, so I didn't have to spend about 25% of what I paid for the whole engine on a new one.

    6) Fuel tank - about 6 months after purchase, the tank started leaking. It was replaced under warranty - apparently there was a problem in the design or manufacture. About three months ago the tank started leaking again. I guess the heat in the tropics was too much for it. I found two stress fractures and sealed them w/ JB Weld, not having access to a plastic welder. Works great unless I tighten down the air bleed screw in the cap - then the pressure builds and pushes a small amount of gas out. Since it rains almost daily here I've addressed this by leaving the thumbscrew slightly open and inverting the top 1/4 of a plastic drink bottle over it. This is held in place w/ small bungee cord attached to a couple of the cowling seal screws I installed in section 1. It's a real Rube Goldberg setup that actually works quite well since, with the bottle cap off, the bottle doubles as a funnel.

    None of these is totally out of line on its own and I've tried to keep a good attitude about it. But cumulatively... I gotta tell you - I think a new outboard ought to be a lot more trouble free than this one has been. I don't believe it's ever run longer than a month w/o something happening. I'd hoped for several trouble-free years of use, but that didn't happen by a long shot. I think it would be fine as a kicker for weekend use in the US where parts are available - if one pays the strictest attention to fuel quality. However, I don't recommend it as a primary tender engine for full-time liveaboard cruising. I'm going to continue muddling along as best I can, but I can tell you right now that my next outboard will not be a Tohatsu 3.5 hp 4-stroke.

    At any rate, thanks again for your help,

    Mark
    Last edited by mkaynor; 09-07-2010 at 12:08 PM.

  7. #7

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    So, anyway, getting back to my problem. I have the parts catalog but no shop manual. It looks like I'll need to split off the power head from the drive shaft housing at the gasket w/ 7 bolts and a couple of alignment pins. Are there any "gotchas" in doing this?

  8. #8
    Join Date
    Mar 2010
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    Buffalo, NY, USA
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    2,080

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Six 6mm bolts with 10mm heads. Two dowel pins. Not a difficult procedure. Pull the bolts, and pop the powerhead off. Should only take a few minutes. I would recommend a new base gasket. The Factory service manual is available from any dealer. Since you are remote, and may have problems finding a dealer, you can also use a Nissan or Merc manual. They are the same motors, so parts interchange as well.
    Paul
    Buffalo NY USA

  9. #9

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Paul,

    Thanks again for your help. I'm going to leave it be for now - it seems to be working fine and I can get along w/o neutral. I'll take it apart one of these days, preferably when I'm not far from a Tohatsu / Nissan / Merc dealer. I'm not averse to making a gasket, but I'd hate to break, lose, or otherwise screw something up when there are no parts around.

    Mark

  10. #10
    Join Date
    Jun 2007
    Location
    TAMPA, FL, USA
    Posts
    1,425

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    One of the two orings on the shift handle failed allowing salt to bind the handle.
    Elvin
    Solution One Maritime

  11. #11

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Elvin,

    I doubt it was salt although it could be corrosion from some other source. The outboard had been run in fresh water only for at least 4 months prior to us leaving it unused for 5 weeks. Thanks for the suggestion, though. When I get around to taking it apart I'll pay special attention to the o-rings.

    Mark

  12. #12

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    I got it fixed. The shift lever shaft was frozen to the housing by corrosion. Tohatsu not including a grease fitting to lube the shaft probably didn't help. I just bought a used Yamaha 4 hp 4-stroke. It's much quieter and seems to be far better engineered. It does have grease fittings. And a fuel pump so I can add an external water seperating fuel filter. The Tohatsu is now in our spares locker. Thanks for all your help.

    Mark

  13. #13
    Join Date
    Jun 2007
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    TAMPA, FL, USA
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    1,425

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Not a corrosion issue as nothing on the shaft corrodes. Its just a build up of sand/salt caused by an o-ring failure.
    Elvin
    Solution One Maritime

  14. #14
    Join Date
    Jan 2011
    Location
    Miami Beach
    Posts
    14

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    I had many of the same problems that you have experienced- cracked fuel tank(replaced), problems reving(comes and goes), stuck gear shift(broke it forcing it and had to have it replaced), etc. and now have a whole new one.

    My Tohatsu 3.5 was running perfectly, however, I forgot to open the air vent screw and when it started to sputter I realized the problem and opened it, while the engine was still running. There was a sucking noise as the pressure was relieved, but afterwards my engine will not rev. It just putters when I start it. I drained the fuel tank, carb and fuel lines, but it still just sputters. Help.

  15. #15
    Join Date
    Mar 2010
    Location
    Buffalo, NY, USA
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    2,080

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    This really belongs in a new thread, as it's a different problem. However... Assuming that you have a MFS3.5A or B...

    You may have developed quite a vacuum in the tank, which may have sucked the float needle into the seat, damaging it. I would check the needle and seat, as well as the float height first.
    Paul
    Buffalo NY USA

  16. #16

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Paul,
    I have had had the same issue with my 3.5hp Tahatsu 4stroke not shifting. I have removed the power head and the shift rod shifts the clutch dog just fine. I can not turn the shift lever rod at all or get it free from the housing. Am I missing something?
    Thanks for any advice in advance,
    2kjh

  17. #17
    Join Date
    Mar 2010
    Location
    Buffalo, NY, USA
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    2,080

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    The shift lever is stuck in the cowling. Disassemble, install new o rings, and grease when reassembling.
    Paul
    Buffalo NY USA

  18. #18

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Thank-you.

  19. #19

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    Hello, me again. I have used this outboard for 9 years on my dinghy in the salt water on the mid coast of Maine. I have had virtually no issues with it other than fuel fouling up the carborator, and corrosion of parts due to the salt environment. I replaced the plug and test ran in a tank with fresh water and new gas. Shifting was difficult, but would shift. The next time I went to use it to get to the boat it would not shift. So of course I forced the shift handle to the point where it broke. I found the procedure for replacing the shifter on this forum. Once I had removed the power head, bottom cowling, and even the tiller it took me two days of penetrating oil and s pipe wrench just to turn the shifter shaft in the casting. I still can not remove the shaft. I have tried punching out with a hammer and punch. I just want to make sure there isn't a set screw or some other keeper hol

  20. #20

    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    [QUOTE=KJH2;578821]Hello, me again. I have used this outboard for 9 years on my dinghy in the salt water on the mid coast of Maine. I have had virtually no issues with it other than fuel fouling up the carborator, and corrosion of parts due to the salt environment. I replaced the plug and test ran in a tank with fresh water and new gas. Shifting was difficult, but would shift. The next time I went to use it to get to the boat it would not shift. So of course I forced the shift handle to the point where it broke. I found the procedure for replacing the shifter on this forum. Once I had removed the power head, bottom cowling, and even the tiller it took me two days of penetrating oil and s pipe wrench just to turn the shifter shaft in the housing. I still can not remove the shaft. I have tried punching out with a hammer and punch. I just want to make sure there isn't a set screw or some other keeper holding the shifter shaft in the housing.
    Thank you in advance for another advice,
    kjh2

  21. #21
    Join Date
    Mar 2010
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    Default Re: Tohatsu 3.5hp 4-stroke shifting problem

    No keeper. See the parts diagram:
    Click image for larger version. 

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    Paul
    Buffalo NY USA

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