Lower unit pressure

[fireman57]

What causes a lower unit to build up pressure and basically explode when you take a fill/drain screw or the philips out (to rebuild). Have had this happen twice in the last three years. Once on a '88 48special and a '77 75hp.

 

[jakedaawg]

Maybe if it got filled on an arctic like day?

 

[fireman57]

Not funny when I get covered in sprayed lower unit lube. Tastes nasty.

 

[jakedaawg]

Oh, come on, its just food for thought

 

[F_R]

All my work shirts had little black dots all over them when I was in the repair business. Fortunately, my beautiful wife was pretty good at getting them clean. Believe it or not, white shirts with lots of starch works best. In one way, presence of pressure in the gearcase is a good sign. It isn't leaking. But it could also be from using the wrong oil (like car oil).

Hey, you ought to drop a Johnson TN lower unit without draining it first. Guaranteed to dump about a pint of oil on your shoes!!

 

[fireman57]

Have dropped plenty of lower units without draining them but never a TN. One engine kept weeping LU oil out the top hole after use but when you would loosen it there was no pressure but also no water in the LU. Never understood that. If there was pressure in it to help keep water out then why would it leak from the top fill hole but not take in water when the engine is off and pressure subsides? Btw, nice to have a helpful suggestion.