I had the same problem a while back with my 3ym30, did all the checks and even have a strainer, had a feeling it was in the heat exchanger, so finally broke down and took it off sure enough some how sea weed had got into it and cut down the flow, put back together and everything works fine except now have two strainers.
09-03-2009 04:09 PM
Yanmar Hi Temp
It would certainly help to know which engine you have, and whether or not it is fresh water cooled. But the previous post is correct. One of the very first things to check is the raw water impeller. And check it closely. There have been some Yanmar impellers that spin the center hub, and unless you check it very closely, will not be noticable. I know this from experience. I now buy Johnson impellers. My Yanmar distributor carries them and they are identical to the Yanmars, with the exception that the pin goes all the way through the impeller on the Johnsons, and the Yanmar is bonded some way. If fresh water cooled, the heat exchanger is pretty high on the list of things to check.
09-03-2009 11:15 AM
ill have to give those a check thank you for putting me in that direction
09-02-2009 11:43 PM
When was your impeller checked last? Is it salt or fresh water cooled? How old is the thermostat and when was it changed/checked last? This is what I would check first if water intake looks clean. Also, you could have picked up a plastic bag or something else that would restrict the flow a great deal.
09-02-2009 11:30 PM
yanmar high temp alarm
had a problem ...returning from a sail, had the motor running at about2800 rpms for about20 mins the high eng temp alarm sounded. prior to the alarm sounding i noticed the exhaust got alot thicker and darker. checked the water flow to eng... seemed a little lite checked the filter coming into the line and it was clean. havent been able to re create problem but i havent run the engine that high since.....any ideas? any help would be appreciated