1993 Tohatsu 90hp PSH removal?

[ntarver0568]

I have a 1993 Tohatsu 90hp, lots of fishing string and a big steel leader got hung up behind the prop, melted the seal and locked up the motor before I realized there was a problem. I spun the starter with a breaker bar and got it loosened up, removed the lower unit and it sounds like something grinding in there. The prop shaft housing is corroded to the lower unit housing; can't get them apart. I already broke the brittle prop shaft housing trying to remove it. Any suggestions on how to remove it? Tried using a big slide hammer in the inner lip and it won't budge.

 

[TOHATSU GURU]

Re: 1993 Tohatsu 90hp PSH removal?

Based on your efforts so far your best bet would be to let a marine mechanic take over before you damage anything else. If you want to go further down the do-it-yourself path your next step would be to use a prop shaft housing puller...

 

[lots of boats]

Re: 1993 Tohatsu 90hp PSH removal?

Hi

When the prop shaft housing i.e the bearing carrier is broken, as you decribed it probably means you put a big washer on the shaft and tried bashing it out, meaning it is really stuck? I would guess there is a good chance the oxidation inside the gear housing, between the bearing carrier and the housing is so far advanced that it is going to be hard to salvage the gear case, if this is the case you dont have much to loose if you heat the housing to expand it a bit and free the bearing carrier from the housing.

Cheers

 

[ntarver0568]

Re: 1993 Tohatsu 90hp PSH removal?

Thanks for the help, used an air saw and cut the inside of the prop shaft housing out and used an air hammer an chiseled the rest out. It was already broke anyway. Ordered a new prop shaft housing assembly, lower bevel gear and a water pump while I'm at it for $285. Not too bad. Cheapest lower unit I could find was $1200. Not worth it.

 

[lots of boats]

Re: 1993 Tohatsu 90hp PSH removal?

Hi

Perfect, I've peeled a few out like that myself. Make sure when you put the new pieces back in you are familiar with the term backlash, and try to get a feel for what gear backlash is, if you don't already know. And my guess is that you may need some kind of goop to seal around the bearing carrier, mercury used to make a sticky sealent, I think was called perfect seal, you put grease on the large O ring and this sticky stuff around the outside of the bearing carrier itself, it sealed the scratches, but you had to make sure it didn't get inside the case.
Good luck.

 

[ntarver0568]

Re: 1993 Tohatsu 90hp PSH removal?

Thanks for the warning, and no I'm not familiar with backlash. Could you explain or possibly point me in the right direction? I'm pretty new to this.

 

[TOHATSU GURU]

Re: 1993 Tohatsu 90hp PSH removal?

When you replace parts on the prop shaft the clearances can and usually do change slightly. Different shimming washers are placed to either reduce or increase to the factory specifications. This is done with a dial indicator. If you just put it back together without doing this you will be rolling the dice on how long it takes to tear up.

 

[lots of boats]

Re: 1993 Tohatsu 90hp PSH removal?

Hi there,

There is probably lots of info in this forum about backlash, and this is something that must be learned about from experience. However, it is just the space between the gear teeth, providing that the gears are set to the correct depth. Since you haven't changed the forward gear shimming, or the shims for the pinion gear you could assume the the pinion gear has the right depth and the backlash between the forward gear at the back of the housing and the pinion gear are correct. This is only an assumption, you can put grease on the dry teeth and turn things to see that the teeth are meshing full depth. the reverse gear backlash is the thing you have possably altered. The interesting thing about the newer motors is that I haven't found shims to adjust the depth of the reverse gear, and every one I have pulled apart has had the reverse gear just fall out of the bearing carrier, on the bench, clunk. However, with other motors you need to know the specification for the amount of backlash, you put a dial guage on the drive shaft, and if the reverse geat needs to be set you add or remove shims to set the depth of the whole bearing carrier. If the tolerances are too close the gears will wear, the oil will overheat etc. If the gears are too loose they don't fit together and don't push on each other full depth. And they clatter. I think you need a book, this is sort of basic knowledge, especially for the tiger torch/air chisel back yard mechanic, and/or ask your local friendly EXPERT dealer to copy a page from the service manual and to recommend which shim kit to buy. Also another Tohatsu quirk is the hole through the prop shaft is really small. I think it is 3mm. Drill it out, and stick a 4mm key in it or a 3/16 SS cotter key, cheap to buy and fits the castle nut better. Have you figured out how to get away from using Tohatsu props? Cheers.