How to check water pump is working properly on 75 Johnson 9.9?

[mp_2008]

I am in the process of a mini overhaul of my 75 Johnson 9.9 10R75C motor and want to make sure the water pump that is in it is working properly. I might replace it regardless since it is somewhat inexpensive, just takes time. I am not sure where the water pump discharge is at on this motor. There is no hole above the waterline here it streams out of like other motors I've seen, but there is a hole it streams out of down the shaft below the water pump intake that I notice water streaming out of after I turn the motor off and tilt it up but idk if that would be where it discharges the water at or not and don't see how you would be able to tell a sufficient amount of water is discharging through the hole to insure the pump is working well since it is far below the water line. There is a big opening in the top-center of the shaft right below the casing where it spits a bit of water and what looks like even a bit of exhaust out but idk if it's the only discharge or what? Any help or advice will be appreciated!

 

[Rick.]

The hole down low is simply a hole to allow for water to drain from the leg. Has nothing to do with the pump operation. The hole below the casing is an indicator of the water pump operation. If your impeller is old then it is a good measure to change it out. A little money spend can save you from an overheat on the water. There should be a consistant amount of water coming from the below casing hole, both exhaust and cooling water. Many times what appears to a pump failure is simply the leg isn't deep enough in the water. Best of luck. Rick.

 

[kbait]

On those motors.. '74-'76, there is no 'pee' indicator, only what sprays out the exhaust relief port on the upper exhaust housing. Water exiting the powerhead flows down, in front of that hole, and some sprays out. You won't see much, if any water out of there before the thermostat opens, allowing water to flow through your powerhead. At low rpm's, the thermo only opens briefly, so you may not see much coming out of there, but at wide open throttle on the lake, it'll pour out. When testing - start the motor in a barrel, making sure the waterpump is submerged, and run at high idle.. checking the head temp near a spark plug base for excessive heat. You should be able to hold your finger there for a couple of seconds.. if it gets hotter, and you splash some water there and it boils away, your not cooling properly. Once water comes out of that port, you know it's pumping and the thermostat is opening. Now slow to lowest idle and test head temp again for a few minutes..

Impellers usually wear and won't pump properly at lowest idle first, so you want to test at a low idle, if you can run it for 5+ minutes and it doesn't overheat, you're likely good. That being said, if you don't know when impeller was changed, or it's been a few years, just change it out..

Good luck!

 

[mp_2008]

Alright, thanks for the info. guys. I think im going to just replace the pump and all including the thermostat to be safe. Is it a pain to replace, what's the best way of getting to the pump, etc.?

 

[kbait]

Google 'leeroy's ramblings'. You'll find his articles on 9.9/15's and it'll describe all servicing in expert fashion! You may want to change impeller then check thermo.. as I stated above, not much, if any, water should spray out when cold, then start spritzing out when thermo opens as engine gets to proper operating temp.. That'll tell you it's functioning. If water shoots out that hole upon startup, thermo may be stuck open, and should be changed.

Good luck!

 

[mp_2008]

Alright, will do. Thanks kbait.

 

[OptsyEagle]

The t-stat is a real pain to check and replace on that model. It is down at the bottom of the cylinder head and you need to remove the latching mechanism for the hood to get at it. Even then it is difficult but the real fun is re-attaching the latch for the hood. Having someone with very small fingers can come in handy.

I would wait on the t-stat for now. Someday you may want to pull the cylinder head and that would be a perfect day to change the t-stat. Much easier with the cylinder head off the motor.

 

[mp_2008]

The t-stat is a real pain to check and replace on that model. It is down at the bottom of the cylinder head and you need to remove the latching mechanism for the hood to get at it. Even then it is difficult but the real fun is re-attaching the latch for the hood. Having someone with very small fingers can come in handy. I would wait on the t-stat for now. Someday you may want to pull the cylinder head and that would be a perfect day to change the t-stat. Much easier with the cylinder head off the motor.

Hmmm... I noticed it looked like a bit of a pain when looking at the schematic/layout. Thanks for the heads up.