lower unit problem

[mrspears1]

i have a 1975 model 85 hp mercury out board motor with a lower unit

problem. the gear oil is mixing with the water requiring it to be drained and

refilled after use. does anyone have a diagnosis and would it require

replacing the lower unit or could it be a less costly solution?

 

[jake505]

Re: lower unit problem

probably a bad seal, could be the prop shaft seal or the seal for the water pump only way really to find out is take it apart and look at the seals. you shouldn't need to replace the lower unit as long as you caught it before the water started corroding the internals and even then you should be able to rebuild it

 

[Jeff_G]

Re: lower unit problem

There are two ways to fix the problem. Take the entire lower unit apart and replace all the seals. May be a good idea due to the age of it. Or you can pressure and vacuum test the gearcase to see which seal is leaking and only fix that one.

 

[Knightgang]

Re: lower unit problem

Most likely just a seal as has been said. Replace and you shoul dbe good to go...

 

[Moody Blue]

Re: lower unit problem

Start with the simple cheap approach.

Replace the gaskets under both the fill and vent screws. Cost about $2.00 and takes 10 minutes to change. Many times these are reused instead of being replaced and they leak. The screws should be quite snug but not super tight.

Refill the LU then water test. If water is still present then another seal is the problem.