1997 20 hp Merc start up and water pump questions.

I just acquired a 1997 Merc 20 hp. I resealed the lower unit and installed a new water pump. A couple of questions that I’m sure someone can answer for me.

I’m not new to Mercury outboards but I never had one with the knob that is used to prime the carb. I didn’t get a manual with this and my internet searches have come back with no results. Th knob can be both rotated and pulled straight out. For a cold start do you simply pull the knob out and pull the starter rope or do you push it in and out to push fuel into the engine? What does rotating the knob do?

Second, I replaced the water pump impeller and all seals. Once started water came out of the tube from the head but it doesn’t come out in a really strong stream like some of the other motors that I have owned. What is more puzzling is that while it is running, there’s a lot of water that comes out of the area , above the lower unit / cavitation plate, where a section of the shift shaft is visible, by the pivot tube. I’m wondering if the upper seal for the copper tube, at the base of the engine block has gone bad and perhaps much of the water being pumped up to the the engine block is leaking back into the exhaust housing. Any thoughts on this?

Thanks in advance for your help.

Pulling the knob out primes the motor and acts like a choke. Turning the knob to the right controls.the high idle for warming up. The pee stream on those will not be strong until the thermostat opens.
This is how i start my 25 hp.
Pump the ball on the fuel line until hard
Pull the knob out and turn all the way to the right
Pull until it starts and wait for it to bog down
Then push the knob in and wait until it starts to rev up
Then turn the knob back to the left until it is idling normally
did the copper tube come out with the water pump? If so you did did you put the copper tube back in the block after it came out? Or did you put it back in attached to the water pump housing?

Thanks flyingscott. That clears up a lot of questions that I had. I’ll have to wait for the spring to start it back up as I am located in the cold north (Toronto area) and the boat / motor will be put in storage over the next couple of days.

The copper tube did come out with the water pump and I reinstalled it that way. Should I have installed the tube in the block first and then hook it up to the pump housing?

Yes the copper tube must go into the hole in the block first. If you left it in the pump housing you probably missed the hole and your motor is receiving no cooling water.

Thx. I braved the cold and dropped the lower unit and installed the copper tube first. I think you are correct the I missed the hole. Fortunately I only ran it for a couple of minutes in the cold.

i had a look at my carb / primer set up and it seems that there is a linkage piece missing. In an exploded parts diagram they call it a fast idle wire. I can see where it clips into the primer assembly but am not sure where the other end attaches. I’ll continue to search on line but if you have some info on this it would be appreciated.

Thanks for your help!

You should only have a short wire that goes to the carb.

Solved the mystery. The previous owner had used the fast idle wire in place of the linkage that prevents starter engagement while in gear. I replaced that linkage when I first bought the motor and kept the “incorrect” linkage in my tool box. I recognized the wire from a parts diagram on line so I had a look under the flywheel and there was a slotted hole for the one end of the wire in the throttle linkage. I fed it through that hole and clipped the other end into the primer and I am now back in business.

Now I just need to 4 months to get it into the water! Thanks for your advice, much appreciated.