Volvo Penta Impeller and Cooling Questions

[security6]

I have a 2000 Larson deck boat with a 1999 Volvo Penta 5.7PEFS (gray engine) in it and a VP Cobra SX drive. The boat is new to me this year and has been running great for the 20 hours or so I have put on it.

I decided to change out the impeller because I had no idea when (if ever) the impeller had been changed. Glad I did it because 7 of the 12 vanes on the old impeller had a chunk missing. Some of the vanes had large pieces missing, and some of the missing pieces were small. That leads me to my first question:

1. Do I need to find the missing impeller pieces? Keep in mind that the engine has never overheated (since I've owned it) and runs perfectly. If I do need to find them, how do I go about doing that?

While I was changing the impeller I noticed that an electrical wire on the thermostat housing was unplugged. I assume that this is a temperature sensor. However, my temperature gauge in the dash works great and tracks water temperature as expected (starts out cold, then stays steady at 173-175 on the gauge.

2. What is the sensor on the side of the thermostat housing?

Thanks!

 

[security6]

Re: Volvo Penta Impeller and Cooling Questions

I'll throw an update here. Took it out yesterday with the new impeller, and it ran fine all day. It may have been a tad cooler, but it is hard to tell (temp gauge goes in 25 degree increments).

 

[acboy]

Re: Volvo Penta Impeller and Cooling Questions

This is my first post.

I had the same question about the missing rubber pieces and I was trying to solve a engine cooling temperature problem. I would troll thru my marina at idle speed for 5 minutes and the engine temperature would come up to operating temperature around 160. Then I would take the boat up to cruising speed and my engine temperature gauge would go from mid point (160) to the lowest reading in 15-20 seconds. I tried a new engine thermostat, but not change in symptoms. Then I spoke with the mechanic at my local Volvo Dealer and he suggested I check the thermostat housing for chunks of rubber from the neglected raw water pump impeller. Purchased a new gasket for the thermostat housing, removed all the hoses from the housing, removed the housing from the engine block, poked with a screwdriver in each hole where the hoses attach and sure enough, three pieces of rubber. Once I removed the pieces, reinstalled and tested on the water, my engine temperature was consistant.

Hope this helps