All, I'm posting this in the event that it might happen to you. I was baffled for a short while but now that it's over, it all makes sense. OK, here are the stats. The engine in my E31 is a 22.5 HP, 3-cylinder Yanmar 3GMF, the F standing for fresh water cooling. There's a round, bronze Buck Algonquin through hull screen on the outside of the hull with 1/4" holes in it, not the scoop style with long slots. All the raw water passes through a Gorco strainer.
Last Sunday we had just left the slip when I detected a hollow, resonant sound coming from the exhaust flange on the port side of the hull. It sounded like the exhaust from a car, not a marine engine. You guessed it, I had no water in the exhaust. I quickly revved in forward to get some speed up, shut the engine down, made a U-turn and headed back into the safety of the slip. I had spare impellors for the raw water pump on board, so no problem or so I thought. Phew, this was going to be an easy and quick fix.....ha, ha. I removed the pump plate and the seemingly intact impellor. Whhaaat? Now I was really puzzled. Why was there no water in the exhaust with a good impellor in the pump? Although all six fins were there, a few of them had age cracks so a new impellor was in order. It turns out that what I thought were the correct impellors onboard were really for my macerator (now marked as such) so the day ended right there. Monday I ordered three replacement impellors, one to use and two spares and they arrived the next day UPS Overnight. I popped a new one in and still no water came from the output of the pump. I could manually turn the pulley and get water to pulse out so I knew the pump was working. I had large amounts of sea water flowing from the seacock, through my Groco strainer and to the intake of the pump so what the heck was up? I called Yanmar and went through the whole thing with one of their helpful tech's. We ruled out a plastic bag in the through hull screen because of the Buck Algonquin design, debris in the strainer (the water in there was crystal clear and free of anything) and an air lock induced from a cork gasket in the strainer. You see, Groco strainers are O-ring sealed and it was supple and sealing well, so persumably no air leak forming an air lock (been there, done that numerous times in the past). He suggested as a long shot, a "bubble" formed in the inner wall of my USCG intake hoses from the seacock to the pump. Apparently the inner lining of the hose can separate from the rest of it and block water flow. He'd seen this happen only three times in his career and somewhere back in my teen hot rod memory it seemed to turn on a light. That not withstanding, this initially made no sense to me as I had tested for good water flow by pulling the hose off the input side of the pump to see lots flow out. But that was sea water PUSHING itself through the hose, not sea water being pulled through by the powerful little belt driven pump. I trotted over to West Marine and of course they were out of 5/8" Coast Guard hose so I ordered enough and more to get the job done. That came in yesterday, I cut the proper lengths and replaced all the old ones with new stuff. When I started the engine, water poured out of the exhaust like gang busters. My friends, please learn from my troubles if this ever happens to you. It was obviously as the Yanmar tech said, a bubble blocking flow when the raw water was being PULLED through the hose. All is well now except we had to scrub our planned passage to Catalina Island and Cruisers Weekend. Glyn Judson, E31 hull #55, Marina del Rey, CA
Last Sunday we had just left the slip when I detected a hollow, resonant sound coming from the exhaust flange on the port side of the hull. It sounded like the exhaust from a car, not a marine engine. You guessed it, I had no water in the exhaust. I quickly revved in forward to get some speed up, shut the engine down, made a U-turn and headed back into the safety of the slip. I had spare impellors for the raw water pump on board, so no problem or so I thought. Phew, this was going to be an easy and quick fix.....ha, ha. I removed the pump plate and the seemingly intact impellor. Whhaaat? Now I was really puzzled. Why was there no water in the exhaust with a good impellor in the pump? Although all six fins were there, a few of them had age cracks so a new impellor was in order. It turns out that what I thought were the correct impellors onboard were really for my macerator (now marked as such) so the day ended right there. Monday I ordered three replacement impellors, one to use and two spares and they arrived the next day UPS Overnight. I popped a new one in and still no water came from the output of the pump. I could manually turn the pulley and get water to pulse out so I knew the pump was working. I had large amounts of sea water flowing from the seacock, through my Groco strainer and to the intake of the pump so what the heck was up? I called Yanmar and went through the whole thing with one of their helpful tech's. We ruled out a plastic bag in the through hull screen because of the Buck Algonquin design, debris in the strainer (the water in there was crystal clear and free of anything) and an air lock induced from a cork gasket in the strainer. You see, Groco strainers are O-ring sealed and it was supple and sealing well, so persumably no air leak forming an air lock (been there, done that numerous times in the past). He suggested as a long shot, a "bubble" formed in the inner wall of my USCG intake hoses from the seacock to the pump. Apparently the inner lining of the hose can separate from the rest of it and block water flow. He'd seen this happen only three times in his career and somewhere back in my teen hot rod memory it seemed to turn on a light. That not withstanding, this initially made no sense to me as I had tested for good water flow by pulling the hose off the input side of the pump to see lots flow out. But that was sea water PUSHING itself through the hose, not sea water being pulled through by the powerful little belt driven pump. I trotted over to West Marine and of course they were out of 5/8" Coast Guard hose so I ordered enough and more to get the job done. That came in yesterday, I cut the proper lengths and replaced all the old ones with new stuff. When I started the engine, water poured out of the exhaust like gang busters. My friends, please learn from my troubles if this ever happens to you. It was obviously as the Yanmar tech said, a bubble blocking flow when the raw water was being PULLED through the hose. All is well now except we had to scrub our planned passage to Catalina Island and Cruisers Weekend. Glyn Judson, E31 hull #55, Marina del Rey, CA