Re: 1975 Johnson 25 hp surging
Hello again Jon. Uhh..there's your problem. That piece of rubber should definitely NOT be there. All passages to and from the t-stat housing should be clear and allow water to pass through with ease. You can check them by pouring some water into the t-stat housing with the t-stat removed. You should see water drain out of the exhaust port of the engine. If not, then the passages may be clogged with debris, silt and/or salt deposits. The real question is where the rubber came from in the first place. It could be a few things. Impellers can/do break down and get sucked up the copper tube into the power head, it may also be a piece of the grommet that either end of the copper tube seats into. There's one on top of the impeller housing and one on the underside of the power head, either of which can break down and get sucked up. It may also just be a piece of the old t-stat gasket. In any event, inspect the aforementioned grommets and replace any that are damaged. You can test the rest of your water passages, but dropping the LU and holding a garden hose on the end of the copper water uptake tube. You should again see water come out of the main exhaust port and/or the t-stat housing, if the cover is off. Give these tricks a try and let us know what you find.
