02 Excalibur 330 Temp Fluctuations?

[FalconEddie]

Yes...me again. Just got this boat. Seems to maintain about 145 or so pretty well, but after I run hard through the course then stop, it goes up to near 160 then in about 10 seconds seems to "catch up" and get back to temp. I have a feeling there might be some impellor shrapnel in the system, but not sure that would react like that. Do I need to be concerned? Any ideas?

[XBIGPUN66]

My opinion is that this is normal operation. This would be the delay in the thermostat opening and the temp sender reporting the value to the ecu and the gages.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[FalconEddie]

OK. I'll watch it and not worry about it. In my old boat with GT40, it ran at same temp but never fluctuated.

[DW SD]

It is good practice to change thermostats every few years, especially for open cooling systems. I might put a new one in as cheap insurance. If it operates the same, then you'll have a good bench line. You'll know it won't stick open soon.

Doug

[rcazwillis]

I have the same year engine, mine stays about 170 during operation. I don't set the fluctuations you are describing. I would start with the thermostat

Sent from my SM-G930V using Tapatalk

[shag]

A 15 degree swing is not much... A sticky thermostat can even cause something like you are reporting. I change impeller every year, and thermostat every 2-3 years... You prob don't have to, but cheap insurance. If you replaced a impeller and found some vanes missing, I would drain the transmission cooler... It likes top catch those pieces...

[Jonny Quest]

When running hard, the engine RPMs run the impeller and water pump at a high level providing a high volume of cooling water throughout the engine. When you pull back to idle, the water velocity and volume decrease and can allow the temperature to creep up.