how is water mxing into my foot oil? 15hp johnson 1988

[stracuzza]

my prop started spinning kinda like it had spun so i bought a new prop but still had the same outcome it sounded like the motor was cavatating, i took the boat outta the water and took off the bottom screw where you change the oil at and about half a cup of water came out, i let it drain out until oil started draining put the screw back in i did not put more foot oil but decided to take the motor back out but haven't checked to see if there was any water in the oil but it did sound the same way while i was riding for about a mile (cavitating) .... anyone have any idea how this water may be coming into the foot and mixing with the oil???

 

[wilde1j]

Re: how is water mxing into my foot oil? 15hp johnson 1988

Test leaking lower unit: Pressure and vacuum test required

1. Drain gear oil
2. Pressurize to no more than 15 psig with air
3. Submerge in water, look for bubbles
4. Possibilities
a. Drive shaft seal
b. Prop shaft seals
c. Shift rod seal
d. Cracked casting
e. Drain/fill screws/seals
5. Repair as needed

 

[g-man22]

Re: how is water mxing into my foot oil? 15hp johnson 1988

never run your outboard with low oil or bad lower unit oil. something so small can make a huge impact on your motor. You need to identify your seal problem for the water comming in then go to your locat marine and pick up some evienrude High Viz lower unit oil. with a pump you can screw into the top of the bottle... the use the lower unit refill instructions from there... Always check your top screw first for level by sticking a small screw driver in the hole and check for high level.. then undo the bottom screw almost all the way and se what comes out..if its bad oil let it drain if its good oil screw it back in and you are good to go.

 

[jtexas]

Re: how is water mxing into my foot oil? 15hp johnson 1988

half a cup is at least 12% of the oil in there, maybe 15 or 20% (I don't know the capacity of that gearcase). Bad idea to run it that low.

Drain the rest of the oil, if there's metal in it you'll have to disassemble & inspect the gears. Otherwise, refill as described above, replace the o-rings on the drain & vent screws. Take it back out for awhile then check for water again. If you find it, follow the procedure described by wild1j.

Possible causes of cavitation: damage, or foreign object (vegetation for example) caught on the lower unit blocking the flow of water over the blades; foreign object stuck in the diffuser ring; damaged prop; damaged antiventilation plate; motor mounted too high on the transom.