By share I assume you suggest a selector valve. If so, that may not be doable if the live well pump is directly connected to the under hull seacock. As mentioned earlier a livewell pump with a secondary output port would be the way to go. The only downside I can think of is that the seacock would typically always be open and on some live well setups, when under speed, the live well will fill even without the pump active. That is easy to check, just open the seacock and go for a ride. Check if the livewell fills without the pump running.