All drip less shaft seals can be adjusted in water and in some case they can even be replaced in water as well depending on the type.
What brand are they?
PSS sometimes can be fixed by cleaning the face seal and adjusting the rubber boot.
Tides Marine seals can also be replaced in water.
on an older boat make sure the surface of the shafts isn’t scored. If it is, the new seal will not change anything and the shaft will have to come out to repair the surface. Just went thru this on the 110 Lazzara I run