1973 Mercury Thunderbolt 200 20hp Water impeller install

Dsage · #1 April 27th, 2009, 07:00 PM

I have a '73 20hp that I'm installing a new water impeller on. I ordered the impeller kit and I have the lower unit off but the kit has 2 o-rings that I can not find where they are located to replace. I do not know if they are even on my motor I know some kits come with extra parts. Any help would be great. Here is a picute of the kit I have and the 2 o-rings are in the centerof the picture at the bottom.

Joshua B · #2 April 27th, 2009, 07:38 PM

Check to see if there's an O-ring directly under the water pump housing. It will most likely be a thick 0-ring. You also have an o-ring on the top of the housing where the shaft runs through.

Motor Boater Bill · #3 April 27th, 2009, 09:13 PM

Is that two o-rings or one o-ring and one seal (metal outside rubber inside)? There should be a seal in the top of the water pump housing and the rubber ring (called a slinger) rides on the shaft just above the pump. The slinger doesn't do much, except maybe keep crud from getting to the seal. The more critical seals are below the water pump, where they keep water out of the lower unit. There is also a large o-ring there around the base of the water pump, but it is larger than anything in your picture.

Dsage · #4 April 28th, 2009, 01:00 AM

I would say it was two O-rings. Then again it might be rubber in the outside and metal on te inside but you said it he other way around.

Question about this statement.

There should be a seal in the top of the water pump housing and the rubber ring (called a slinger) rides on the shaft just above the pump.

Heres is what I did. I took off the 2 old gaskets and metal plate. They went back on like so, gasket, metal palte gasket. I then put on the impeller and then the water pump housing. I was about to put on the large rubber piece that in the picture is just below the water pump tube and button everything up when I looked in the packet and noticed the 2 o-rings left. Is the rubber thing below the water pump tube the slinger? I'm sorry if I sound stupid about this I'm more of a car enine guy. And well my boat dealer in town went under and that left one place that I would not take a boat to if you paid me. My only other option is the Big Box Sport stores and they are over an hours drive.

Dsage · #5 April 28th, 2009, 06:21 PM

Does any one know where I can find a diagram of the lower unit with it parts I found one site but the picture was so blurry it was not able to be used plus it only had have the parts numbered and labeled. I think if I had the diagram I could figure out the o-rings.