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  Mercury Gear Case and Water Pump Rebuild

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Author Topic:   Mercury Gear Case and Water Pump Rebuild
Anjin posted 11-07-2009 05:12 PM ET (US)   Profile for Anjin   Send Email to Anjin  
I read a recent thread about the frequency with which one should rebuild a water pump. I have a 2005 Mercury three-cylinder two-cycle carburetor Saltwater outboard. The water pump has never been rebuilt, but the above mentioned thread has made me concerned about the removal of the bolts and nuts. So I am going to do it no, but have questions.

The shift linkage--on other outboards I have had, the gearshift linkage has to be disconnected. The service manual on this motor doesn't mention gearshift linkage as part of the removal and installation of the lower unit. Just remove 2 nuts on each side and one on the bottom of the anti cavitation plate and remove. Is that correct?

The service manual mentions use of 271 thread locker on gear housing retaining screws, on the upper and lower oil seals and on water pump screws. One of the posts in above mentioned thread mentions use of "never seize". the service manual does not mention use of never seize. What are yout suggestions regarding where to use "never seize" and where to use 271 thread locker?

The service manual mentions use of a special tool called an oil seal driver (part no. 91-13949) to install the seals. What suggestions do you have re: this special tool? Is it really needed? not needed? buy it?

Do you have any other suggestions on doing this job on this particular motor? I want to do this the right way. Thanks.

jimh posted 11-08-2009 08:24 AM ET (US)     Profile for jimh  Send Email to jimh     
Some outboard engines, notably OMC designs, use a gear shift link that moves up and down to effect the shift. Many Mercury engines use a gear shift link with a splined shaft that rotates to effect the shift. When removing the gear case the splined shaft is not captivated in the power head, so there is no retaining fastener to remove.
Anjin posted 11-08-2009 04:43 PM ET (US)     Profile for Anjin  Send Email to Anjin     
Jimh: Thanks for your response.

I studied the service manual more carefully and realized that the seals are removed and the seal driver tool is used only if you remove the water pump base. If one is only going to install a new impeller, plate and gaskets then removal of the water pump base is not necessary correct?

The impeller replacement kit includes a water pump face seal. Instructions say "position the seal with lips facing downward..." One side of the seal flares outward. Is this outward flaring side the side with the lips that face downward?

The kit includes two large bright orange o-rings which seem to be the same diameter as the drive shaft. The service manual and the instructions don't mention these o-rings. Does anyone know what they are for?

The kit also includes two small metal washers coated with yellow plastic. These look like Yamaha gearcase fill/drain screw washers. The ones I have always been sold for Mercury were blue and the Mercury has three fill/drain screws. Are these yellow washers for the gearcase fill/drain screws?

The kit also includes one small (smaller diameter than the yellow washers) dark orange washer. No mention of it either in the manual or instructions. Does anyone know what this washer is for?

Finally the manual says to torque the nuts that hold the gearcase to the drive shaft housing but there is no room to put a torque wrench and socket to the nuts. So how do you torque the nuts under these circumstances?

I apologize for all these questions but the service manual and instructions lack all these details. I would appreciate some feedback from people who have done the water pumps on these Mercury 90 hp motors. Thanks.

weekendwarrior posted 11-08-2009 07:58 PM ET (US)     Profile for weekendwarrior  Send Email to weekendwarrior     
If the manual states thread locker, then use thres locker. Always follow the manual for things like that.

As for the torque wrench; see if you can get in there with a crows foot socket. If yes, then if you can use it with the crows foot 90-degrees to the torque wrench then the torque reading will be accurate. If you have to stick the crows foot strait out then you'll need to do a little math to calculate what to set the wrench to so that you get the proper torque. The manual for your torque wrench will have the equation in it. Good luck!

Tohsgib posted 11-09-2009 12:27 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
You do not need to torque a lower unit, nor do you need to jam them on real tight. Just snug them all up and then tighten with a 3/8 socket drive...no biggie.

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