For future reference -
Not wanting to trust old o-rings of unknown vintage and having no spares, I tried buying speed xdcr rings from a hydraulic hose supplier. Four of them cost $14.67 and they were ever so slightly too big for the groove, so the sensor would not go back in the thru-hull.
I was able to match one at ACE Hardware in the plumbing area and four cost $1.91. There was a number on the bin starting with SBD but enough o-rings were in the wrong compartment that it's better not to risk relating a wrong number here.
Not wanting to trust old o-rings of unknown vintage and having no spares, I tried buying speed xdcr rings from a hydraulic hose supplier. Four of them cost $14.67 and they were ever so slightly too big for the groove, so the sensor would not go back in the thru-hull.
I was able to match one at ACE Hardware in the plumbing area and four cost $1.91. There was a number on the bin starting with SBD but enough o-rings were in the wrong compartment that it's better not to risk relating a wrong number here.