Tohatsu M40C Troubles

I have an M40C motor on my pontoon boat with a lower unit issue. The motor is fairly old, I would guess mid 90's but I am not really sure since I am the second owner, but in great shape with compression of 110 on each lung. Late last year the boat began grinding when going into reverse (forward was fine) and after an adjustment of the shift cable the reverse problems were solved. Last trip out last year the engine would not stay in reverse, the shift lever would chatter when it was placed in reverse but if you held it down reverse would work fine.

I have ordered a service manual for the motor and should receive it Monday. My quetion is 3 fold: 1) am I right that I need to tear into the lower unit? 2) I am mechanically inclinded but not a pro, am I fooling myself thinking I can do the repairs? 3) this motor resides at our vacation home (is at my main home now) where I just want to go and have fun, not spend time working on a boat motor... Aside from a water pump rebuild what other services would be wise to do now?

Sorry to be a taker on my first post, but thanks all for the great information you contribute to this site.

Thanks in advance,
Scott

Re: Tohatsu M40C Troubles

1. Yes, the issue is at the LU, but you may not need to pull it apart. The reverse problem could be as simple as a shift cable adjustment, or you may need some gears (or clutch dog). You may also need the shifter detent/ball checked. Would need to see/inspect the motor to determine the exact problem. Was the LU lube changed after the last cable adjustment? If the gears were grinding, it is important to change the lube, to flush out any metal shavings.
2. If you have basic machanical skills, good tools, patience, and are armed with the Factory service manual, you should be able to tackle the repair.
3. Any OB should have routine maintenance, including wp kit, fuel filter, and LU lube changes periodically.

Re: Tohatsu M40C Troubles

Thanks for the advise. I got the service manual and it all looks do-able, just a bit intimidated with the shimming...

When I drained the fluid from the lower unit there were metal pieces in there... I guess my first question has been answered.

Re: Tohatsu M40C Troubles

" Late last year the boat began grinding when going into reverse "

Were you slowly shifting the engine into gear?

Re: Tohatsu M40C Troubles

No, wasn't slow on the shift....
I have taken the lower unti apart and see the clutch dogs and engatement points on the forward and reverse gear are slightly rounded off. I am going to order new pieces for the lower unit and rebuild it. I still need to find my root cause though. I guess it is possible that just the age of the motor and a fair amount of use have caused the issue but what I am a little concerned about is that to get the motor into reverse the shift cable was at the end of its adjustability so I wonder if I possibly have an issue with the control box or a streched cable?

Also is there a trick to removing the shifter mechanism? I can see there is a slight dimple on it from where the pin rides but I cannot get the assembly out, tried some penetrant, have removed the bolt that may or may not hold it in and still can't get it to budge. I am worried if I really try to get it out I will damage the housing.

Thanks for the help

Re: Tohatsu M40C Troubles

Regarding the shifter cable, keep in mind that there are clevis adjustments at both ends; If one end is off, the other end needs to be off (in the other direction) to compensate and end up in position. That is sometimes the case.

Removing the cam rod and cam is just a matter of removing the retainer and bolt and giving a stiff tug upward to extract the cam. The bushing has both inner and outer o-rings which probably ought to be replaced while everything is apart.

Re: Tohatsu M40C Troubles

Thanks Paul. It is taking much more then a firm tug. I have resorted to putting a pair of vise grips up near the sleeve that connects the 2 parts of the shifter linkage and hitting the vise grips with a dead blow. It is still not budging. I am hesitant to heat it...

Re: Tohatsu M40C Troubles

Check to see whether there is corrosion holding the bushing.

Re: Tohatsu M40C Troubles

I am sure it is corroded, any suggestion on how to free it aside from soaking it in penetrant?

Re: Tohatsu M40C Troubles

Vice grips on the shaft and a hammer.