Saildrives have the problem of debris inside the leg even though the water inlet holes in the bottom of the leg are small. Check this – close the engine water inlet after stopping the engine. Take the hose off open the valve and if water does not gush out poke a stick down the hole until it does gush out. Reconnect the hose with 2 hose clips and turn the valve back on. It worked on mine. There was weed and stuff inside the leg blocking the hole through the hull. I now have a stick hanging in the engine compartment for this purpose.