1998 Mercury 20 hp jet - no propulsion

[eli2]

Had the boat out yesterday when the engine suddenly revved up and we seemed to lose water propulsion from the pump. All we have is exhaust coming out. We checked for obstructions on the grates or stuff wedged in the pump. Any help would be appreciated.

 

[redrum]

I'm going to bet you sheared the impeller key. That is an easy fix. Just take the shoe off, zip off the impeller nut with an impact, slide the impeller off and check the key that holds the impeller to the shaft.

I've had trouble getting the impeller off my Merc 25 before. I usually use two long screw drivers to pop it loose. Before you put it back on I would suggest using anti-seize on the lower portion of the shaft. Since i've started using anti-seize I've been able to pull the impeller off by hand.

 

[eli2]

If that is the problem, are there special keys that should be used?

 

[eli2]

Found the impeller key broken. Thanks for the input redrum.

 

[eli2]

One more question, is there a torque spec on the impeller nut? When I took it apart it was finger tight.

 

[turbotodd]

If the foot is the same as the Yamaha's that I'm familiar with, the nut isn't much more than finger tight. The lock plate holds it on. Under the nut are some washers and IIRC there are two plastic washers that keep tension on the impeller/nut.

Check with outboard jets (name of the company)-they can either fax or email you instructions on how everything goes back together. And you can get some new impeller keys as well. Keep a few for spares. A rock gets into the pump and it'll shear the key off, exactly like it's supposed to. Also if the impeller nut was not tight enough, the impeller rattling back and forth will do the same thing.

Jets aren't exactly maintenance free unfortunately.

 

[eli2]

Thanks, you guys have been most helpful.