2003 Sport 216, Excalibur 330 - Raw Water - Weird Eng. Temperature Occuring

[peteb]

Here is an issue that has got me stumped. I know my way around the PCM raw water cooling package pretty well and have always done all my own work related to the cooling system. Not a mechanic by any means though. I switched out the TStat to the normal 160 degree one a few weeks ago after the temps were acting crazy one day on the water. Boat was and still is sucking water good, strainer is clear and it has plenty of fresh water to cool the engine. Last few times boat runs like its supposed too at 159-161 temps which is ideal. After dropping anchor and sitting for a while after a few ski runs the boat temp only gets ups to like 115 and 120 when crusing. Its like the tstat is stuck open after sitting when the engine temps rise when the engine shuts off after skiing. Never had this issue before so asking any thoughts.

[Jonny Quest]

First thing I would do is confirm that the temp gauge and sending unit are working properly. I have an infra-red temperature "gun" that I can shoot the temps at various locations: thermostat housing (before & after), risers, block etc. - anywhere that cooling water is circulating in the engine. That may provide more info on what's going on and where to start looking.

JQ

[NautiqueJeff]

If you have ever had an impeller fail, the vanes can end up getting stuck in the thermostat, preventing it from closing.

[peteb]

Should have the problem solved. I ripped everything apart for the fill riser upper, fill riser, tstat and flushed the enitre system and inspected for a potential blockage. Put it all back together and took the boat our for some sets to see how it did on temp. Once the boat came up to temp and the stat opened around 165 it ran fine but then started temps dropping to 145 ish. Drove me crazy since the performance wasn't up to par. Ripped everything apart again and took the stat out and took it home to check it. Went back to basic engineering and the stat opened in a pot of water on the stove around 165-170 degrees correctly. So then I took the pot of hot water and slowly added cold water to bring the temp down. Stat was faulty and would not close. Pushed the stat bottom and it closed fully. Tried it again and this time after it opened in the hot water I hit it hard wiht cold water under the sink and still stuck open. The thermostat was brand new so I will contact them tomorrow to send me the replacement. Bought a new one at the local dealer and put it in and we will run it hard today. Will post the final results.

[Interjon]

Love the persistence peteb. Well done.