Hi everybody, Good day, I am new here, Maybe someone can have a clue. I have a volvo Penta 4.3GL, raw water cooled and used in sea water.
when I run the boat on high rpm (above 3000) the engine works fine and temp stays stable 85 deg celcius. But after 15 minute ride and I lower the revs to 2500 and under, the temp starts going up to 97 deg C. When idle makes it worse, I rev the engine for 5 seconds and the temp start going down to normal And keeps going like this for a while untill it gets stable. But I have to rev the engine say 4 times or more to get it stable. I noticed as well that when driving on plane at 3600rpm, the risers are hotter than normal, but you stiil touch them with you hands. I am thinking that there is a lack of water flow. Checked the impellor and it is in new condition as I changed it begining of last season. Some body told me to start from the thermostat housing to sea if there is any blocking but I was surprised that I made 30minute trip at 3900 rpm and temp stayed stable on 85 deg C, than when I lower revs the problem starts. Thanks for any help.
when I run the boat on high rpm (above 3000) the engine works fine and temp stays stable 85 deg celcius. But after 15 minute ride and I lower the revs to 2500 and under, the temp starts going up to 97 deg C. When idle makes it worse, I rev the engine for 5 seconds and the temp start going down to normal And keeps going like this for a while untill it gets stable. But I have to rev the engine say 4 times or more to get it stable. I noticed as well that when driving on plane at 3600rpm, the risers are hotter than normal, but you stiil touch them with you hands. I am thinking that there is a lack of water flow. Checked the impellor and it is in new condition as I changed it begining of last season. Some body told me to start from the thermostat housing to sea if there is any blocking but I was surprised that I made 30minute trip at 3900 rpm and temp stayed stable on 85 deg C, than when I lower revs the problem starts. Thanks for any help.