Gear oil question Johnson 30HP

[Jim Hawkins]

I went to change the gear oil on my 1987 Johnson 30HP. I should have done this when I first got it, but I didn't. After running it several hours I decided not to push my luck. When I removed both plugs nothing came out. When I began pumping new gear oil in on the second pump a blob of brown oil came out the top hole and on the third pump the new oil was coming out. It could not even have taken 1 oz. of oil before it overflowed at the top hole.

Short of disassembling the lower unit, any suggestions?

*Note - running the motor all seemed well and shifting was Very smooth.

 

[HighTrim]

Re: Gear oil question Johnson 30HP

Flush it thoroughally with diesel then refill.

 

[Vic.S]

Re: Gear oil question Johnson 30HP

I agree flush it out. If you use diesel oil be sure to drain it thoroughly before refilling.

New seals on the drain and level plugs are usually recommended.

Check the new oil stays "clear and bright" Any cloudiness indicates water is entering.

 

[Jim Hawkins]

Re: Gear oil question Johnson 30HP

I anticipated that suggestion and tried pumping in kerosene. The kerosene just comes out the top hole almost immediately. I probably got 1/2 oz in there. I'll let it sit overnight, drain in the morn, refill with more kerosene and run the motor in gear for a minute or so and see what comes out.

Just got an idea, I'll hook the pump hose up to the lower hole and see what a shop vac can suck out. The tube is clear so I can stop before getting anything flammable into the vac motor.

 

[Vintin]

Re: Gear oil question Johnson 30HP

Sounds like it was pumped full of grease like is done to some of the older lower gear units.

 

[Jim Hawkins]

Re: Gear oil question Johnson 30HP

Sounds like it was pumped full of grease like is done to some of the older lower gear units.

Is that a bad thing? I guess better than air or water.

And was that done instead of fixing leaky seals?

 

[HighTrim]

Re: Gear oil question Johnson 30HP

Yes

 

[schematic]

Re: Gear oil question Johnson 30HP

I anticipated that suggestion and tried pumping in kerosene. The kerosene just comes out the top hole almost immediately. I probably got 1/2 oz in there. I'll let it sit overnight, drain in the morn, refill with more kerosene and run the motor in gear for a minute or so and see what comes out.

Just got an idea, I'll hook the pump hose up to the lower hole and see what a shop vac can suck out. The tube is clear so I can stop before getting anything flammable into the vac motor.

Heat the gearcase with a heat gun or heat lamp. apply compressed air (<10psi)to the "level" hole and grease will exit drain hole......much safer

 

[Jim Hawkins]

Re: Gear oil question Johnson 30HP

This morn I drained and refilled with kerosene. Ran it in gear for a minute and drained. Used compressed air to blow out more gunk, refilled w/ kerosene... After a few times the kerosene ran out with only a light brown tint. I pumped the gear oil in, It took about 8 oz. I'll change it again after I next use the boat. Checking it after it sat all day no oil had run out but I'll see what it does after it's been in use.

Thank you all for the help and advice.