Sounds like VRO to me also, be it filter, pump or whatever. I had twin 89 Johnson 150's that would alarm when oil was low or not getting to your engine. Overheat was a different alarm. I think over heat was a steady alarm (picked up a bag once so that is how I know for sure) where the oil was intermittent. Check your engine book for what your particular alarm is. Boats do not like to sit. Could certainly be impeller/thermostat issues as well. Was it ******* OK?
Easy enough to check the suggested above and if you don't find any issues at least you know you have a new impeller (which in that time is likely due to be replaced anyway).
If it is VRO related you can check the oil feed to make sure it is ok. Also pull your plugs and look for any metal shaving on them (not a good sign). If it is VRO related and it ran on low oil then stopped you may have done some damage to the cylinder walls which should show on your plug. After that best to let the mechanic look at it.
I will also second Bill Biggart in Plaistow. Very good and as honest as they come, at least in my experience with him.