impeller?water pump?, milky gear oil

[SpokaneBassPro]

I have a Johnson Super Sea Horse 40 hp and it recently has had some seriously lacking performance. Generally will go about 30 mph and now will go only about 14-15 mph. Drained lower unit gear oil and it was off color and milky. Replaced it and went out on the water, same thing happened after about 25 minutes. I pulled back casing from lower unit off and noticed the rubber gasket halfway down the driveshaft also had the milky fluid all over it. If the impeller or water pump needs replacing how would I go about doing this? I am not sure of the year but some numbers I have pulled off it are 307770, 307759, and 307806AC. Any ideas?

 

[fireman57]

Re: impeller?water pump?, milky gear oil

First thing is to get an OEM manual. These have all the pics, tricks, and info in them. You need to pull the lower unit and replace all the seals. While you are there put in a new impeller and don't forget to change the drain and fill screw seals. I don't think your lower unit woes have anything to do with you losing speed. Next time pump the primer bulb to see if it picks up speed. Also do a spark check while underway with a disposable buddy and a pair of insulated pliers to make sure that you have spark to all cylinders. Model number should be found on the mounting bracket below the engine or on a welsh plug on the engine.