Hello, new to the forums and looking for some advice.

We recently purchased a 1984 Carver 3207 Aft Cabin with an Onan 6.5kw Marine Genset. The generator ran great for a couple of trips but just yesterday I went to start it and it did not appear to be circulating any water (this is a freshwater cooled system). I assume there must be a safety shutoff as the generator powered itself down after about 60 seconds.

I am thinking that I will need to replace the impeller but have read that it may have just lost siphon? Is that possible, and if so any hints on how to remedy?
Is it a big job to replace the raw water impeller?
Does anyone have a manual for that year Onan generator?

I have owned many inboard/v drive boats as well as a few older RV's and have done all the work on them myself.

I searched the forums but could not find anything specific to my year/model.

Thank you in advance for any expertise you can provide!