Random temperature spike

[further]

Hi All,
2004 5.0GXI-D. Runs well. Just replaced impeller and thermostat as part of regular maintenance and as a result of this random temp spike occurring last season as well thinking it may have been the Tstat sticking. However, today during cruising around 2k rpm temp spiked to about 190. Usually hovers around 150-160. Temp spiked and I brought it back down to idle and lifted engine bay. Nothing felt or looked overly hot. Back to the helm and temp started gradually decreasing. This has happened a few times in the past. Last year temp spiked to over 200. No alarms. Could it be the temp sensor or switch?

 

[Fun Times]

What stern drive model do you have?

Often one of the usual suspects to consider checking on the Volvo drive of what I believe to be your type model is the water rubber seals found in between the upper and lower stern drive housing as they age out they start to allow air to get in the water flow cooling system...Usually it takes putting clear water hose inline right at the impeller housing and searching for air bubbles in the flow to find it.

As a starting test for you, try running the engine on the garden hose with just moderate pressure while using an infrared thermometer gun to see if the temp is matching the gauge both at normal temp and see if it's truly spiking because in theory running on the hose would help allow more air should the drive seals be an issue such as up on plane the drive is higher vs slowing down and submerging the drive.

Was the impeller and housing okey looking, no big grooves from sand, etc.?
You put in the same size impeller and for sure the correct impeller part number when in both last time (year/season etc.) and this time? There are different sizes of impellers and getting the right one is important for this spike reason is why I mention this.

 

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Thanks for the reply. Sterndrive model SX-M 1.79. No issues with impeller housing and impeller. I replace impeller every other year and remove outdrive annually to store and check alignment/grease U-joints. Boat is in the slip from May to October. Only time I run on a hose is just before I put in for the season to make sure all is good. Run in the driveway to get up to temp about a week ago before I put in and no spike. Will use infrared thermometer when I’m out next time. Any other tests that can be done while in the water?

 

[Scott Danforth]

Check the raw water fitting that feeds the hose to the transom shield

 

[further]

Check the raw water fitting that feeds the hose to the transom shield

Checked prior to installing outdrive for season. Was clear… nothing unusual visually anyway

 

[Scott Danforth]

Look to see if it's cracked