re: Johnson 35 outboard troubleshooting

My dad has a 76 9.9 and not sure if the 35 is the same but until 78 the smaller johnsons didn't have a true tell-tale for the water system. The hole at the back is just a blubber hole that exhaust and spray will still come out of even if there's not good flow from the water pump. If you're familiar with it you can tell but it's tricky.

I would definitely change the impeller, and flush out the water passage while you have the lower unit off.