Did you watch the pump each time the water stopped? I think your belt may be slipping when you throttle up.
Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Sun, Jun 4, 2017, 1:08 AM DON JONSSON via CnC-List <[email protected]> wrote: > Hello > > Today on the first trip out for the weekend on the boat I got about 5 > minutes out and the engine over heated. Spent the next 3 hours trying to > figure it out before towing the boat back in with the dinghy. Another 2 > hours at the dock and still no luck. Perhaps someone can help. > > First it is a Yanmar 3GMD with is a raw water cooled engine. Here is what > was tried. > > 1. When the alarm went checked that indeed no water pumping was the issue > and turned the engine off and dropped an anchor. > > 2. Checked from the through hull to strainer and it was fine, no blockage. > > 3. Checked downstream of the pump and found no water. Thought, "that was > easy". Not. Took the pump off and the bushing on the impeller had given > up and the impeller wasn't spinning. It is only a year old, but whatever, > put a new one in. Now water was coming out of the pump but still not going > through the engine. Wondered whether back pressure from a plug downstream > had caused the impeller to fail. > > 4. Systematically went through every location that you can check all the > way to the riser on the exhaust and everything was clear. The riser is > brand new and there are no blockages there. You could blow freely through > hoses and the engine. Water was coming but not enough water. > > 5. Tested the thermostat in hot water, it opened no problem. > > 6. Started at the beginning again and this time ran the engine a bit at > each spot. What we found was that the water would be fine until we rev'd up > the engine and which point the water would slow down and stop. When we > went down to an idle it would start again. This could be repeated over and > over again. Except immediately downstream of the water pump where there > was always water with pressure. > > 7. Took out the thermostat and tried this test down stream of it. Same > problem. We assumed in the case the water, or at least not all of it, > wouldn't even be going through the engine. > > 8. Flushed water forwards and backwards through the engine. No problem > and no debris. > > 9. Figure there must be air coming at the strainer and put in a new > gasket and checked for cracks. Same problem. > > Opinions are: > > 1. There is still a problem with air somewhere before or in the pump. But > where? And why no water. > > 2. At the T where water goes into the cylinder jacket there is something > wrong going on, but it is not easy to remove. > > 3. If it is a blockage in the engine then when there is no thermostat in > the engine these symptoms should not occur downstream of the thermostat, > but they do. > > 4. If it is in the engine, when the thermostat is in and the engine is > cold you should get water, but you don't. > > > Tomorrow we will start again, but if anyone has any ideas it would be > appreciated. > > Don Jonsson > Swan Song, C&C 34 > Victoria > > Sent from my iPad > _______________________________________________ > > This list is supported by the generous donations of our members. If you > wish to make a contribution to offset our costs, please go to: > https://www.paypal.me/stumurray > > All Contributions are greatly appreciated! >
_______________________________________________ This list is supported by the generous donations of our members. If you wish to make a contribution to offset our costs, please go to: https://www.paypal.me/stumurray All Contributions are greatly appreciated!
