Evadne
Well-Known Member
Last summer, at the start of the summer holidays (of course) the trusty Yanmar decided to play up big time. I've seen the symptoms described a few times before, and I think I've cracked it, but thought I'd share it in case anyone else is still at the head scratching stage.
At the time the symptoms were overheating, lots of white smoke, not running well. A bit of investigative work revealed that while the engine would start up and run in tickover forever, if you tried to run at anything like normal revs, when the thermostat opened the water flow would almost cease and overheating occurred. Running at tickover for 20 minutes beforehand to get everything thoroughly warmed up seemed to do the trick.
Now, although it really looked as if there was a blockage somewhere in the waterways, advice from fellow forumites indicated that delamination of the exhaust hose was most likely to blame and, the hose being 23 years old, I had a course of action.
Yesterday was the day, and an hour or so of "Bilge grovelling" had the system out. The hose, of course is as clean as a whistle. The pictures below show the culprit: the top one is the waterlock, the next is the inlet end and baffle, the last is the aft end showing the dipping pipe and baffle:
The welds on the baffle had failed and it became trapped under the dipping outlet pipe, closing it off at higher exhaust pressures. You couldn't get the plate to stay under there on purpose if you tried. /forums/images/graemlins/confused.gif
The lessons? Stainless steel waterlocks should be replaced. Exhaust hose can last longer than you'd expect. This was marked Volvo Penta, probably cost a fortune and is inlaid with gold plated titanium wire with hand laid with the skin of an endangered shark by Swedish millionaires. Sometimes, when you pay top dollar you get good stuff. I'll be replacing it with something cheap and nasty. /forums/images/graemlins/smile.gif
Dave
At the time the symptoms were overheating, lots of white smoke, not running well. A bit of investigative work revealed that while the engine would start up and run in tickover forever, if you tried to run at anything like normal revs, when the thermostat opened the water flow would almost cease and overheating occurred. Running at tickover for 20 minutes beforehand to get everything thoroughly warmed up seemed to do the trick.
Now, although it really looked as if there was a blockage somewhere in the waterways, advice from fellow forumites indicated that delamination of the exhaust hose was most likely to blame and, the hose being 23 years old, I had a course of action.
Yesterday was the day, and an hour or so of "Bilge grovelling" had the system out. The hose, of course is as clean as a whistle. The pictures below show the culprit: the top one is the waterlock, the next is the inlet end and baffle, the last is the aft end showing the dipping pipe and baffle:
The welds on the baffle had failed and it became trapped under the dipping outlet pipe, closing it off at higher exhaust pressures. You couldn't get the plate to stay under there on purpose if you tried. /forums/images/graemlins/confused.gif
The lessons? Stainless steel waterlocks should be replaced. Exhaust hose can last longer than you'd expect. This was marked Volvo Penta, probably cost a fortune and is inlaid with gold plated titanium wire with hand laid with the skin of an endangered shark by Swedish millionaires. Sometimes, when you pay top dollar you get good stuff. I'll be replacing it with something cheap and nasty. /forums/images/graemlins/smile.gif
Dave
