I have a 74 70hp and it's the same way. They dont have the pee hole that you can look back and see so you have 3 choices. A, hope the water intake never clogs and keep the impeller in good shape, B. put a water pressure gueage in C. make a pee hole. Those where the choices i got from my post. I am going to be researching the options. Good luck.<br />Scott
I think the 1978 should have one, might be mistaken. I can't remember the cutoff year when they started adding them. I've got one on my 1980. If you pull the hood off and note a black rubber hose leading from the exhaust cover (located on the port side) to a plastic fixture in the belly pan cowling then you've got a tell-tale. It's possible it's clogged....<br />- Scott
I have a 1975 Johnson 70HP and it has a tell-tale on it. Chinewalkers instructions are pretty accurate as to try and locate it. If you don't have one you can always look at the exhaust pressure relief at idle and see if there is water coming out. But I would put a water pressure gauge in I I didn't have a tell-tale.
