75 HP Mercury starting problems

I have a 1978 7.5 hp Mercury t

I have a 1978 7.5 hp Mercury that takes a ton of pulls to get it started. When pulling it you can tell when it is going to start because it makes a slightly different noise and is easier to pull about 2/3 the way through the pull. Once it does start it stops after about 10 seconds and I notice it is not pumping any water. Is there an automatic shutoff or thermostat on these motors? I probably have to replace the impeller which is no big deal. Any ideas in why it will not start or what that means when it is easier to pull every once in a while?

Thanks!

Is your choke working properly

Is your choke working properly? You do not have an automatic shutoff. What is the history of the motor? Did it just start doing this?

"Yeah, the choke is working pr

"Yeah, the choke is working properly. It does have the kill button which is just a button on the side of the motor that you push and stops the engine. I just picked this motor up and believe it has been sitting for a year at least. I cleaned the carb with some carb cleaner but maybe need to take it apart and do a thorough cleaning."

"Assume it has been sitting fo

"Assume it has been sitting for "many years" and was not properly layed up.

Pull, disassemble and clean the carb. Replace the plugs, impeller and lower gear oil. Check the fuel filter and all wiring/hoses for serviceability.

Of course, test the compression and confirm spark "first" before you put too much money and effort into this...."

I know that is does have spark

I know that is does have spark because I have started it before and it runs very smooth for a little while. I will pull the carb hopefully tonight and clean it well and see if that helps.

Thank you!