My 89 Saltare hydro-locked, and it came through the exhaust. From what I've learned, without the flaps, if you rev the motor and then shut it off quickly it will siphon water through the exhaust and into the cylinders. If you do a power reverse and shut it off quickly, it will siphon water through the exhaust. There is a diverter in the riser that will prevent that, but with older boats that diverter can rust and become ineffective. A hydro-locked motor, however will not turn over, because the cylinders are full of water. So, if it turns over, hydro-locking is not the problem. If you have milky oil, it can be a head gasket, a crack in the exhaust manifold or a cracked block. A crack in the exhaust manifold will only bring water in after the motor is turned off. If you change your oil run the motor and it is not milky, turn it off and wait a day. Start it and run for a while, if it’s milky it’s a exhaust manifold/water jacket. To check for a blown head gasket do a compression check. If it’s blown, you’ll have two, or more cylinders right next to each other with no compression. A cracked block will show blue smoke at the exhaust, low compression and poor performance.
