DT 9.9 gear oil has water

[karlkork]

I drained the oil in the lower gear unit of my 86 dt 9.9 and found it to be milky indicating
that water was entering some how. There is no evidence of leaking oil from either of the
two ports. Any ideas on where to look for the leak and to remedy it?

 

[99yam40]

Re: DT 9.9 gear oil has water

pressure/vacuum test lower unit to find where it is leaking

 

[karlkork]

Re: DT 9.9 gear oil has water

Not sure how to perform this test and not sure what to do with the results. Is there an obvious seal
that is the culprit in this leak? Karl

 

[99yam40]

Re: DT 9.9 gear oil has water

service manual has steps and procedures
and is worth the money to own if you plan on working on this motor yourself

there are seals on drive shaft, shift shaft, and the prop shaft

 

[robert graham]

Re: DT 9.9 gear oil has water

There's only a few seals that can leak, the drive shaft seal on top of lower unit, the shift shaft seal also on top of lower unit, the prop shaft seal which are located behind the prop, and the 2 drain/vent plug washer/seals under each plug/screw. Remove prop to inspect for fishing line under prop shaft seal, then carefully inspect/replace those 2 flat fiber washer/seals under the plug/screws....The book says these 2 washers should be replaced with new ones each time unit is drained.

 

[karlkork]

Re: DT 9.9 gear oil has water

Thanks for the help. I have the manual and will attempt to replace the seals. Karl