Mercruiser 165 oil cap?

[glennj3]

This is my 2nd engine the other was a 170, essentially the same. This one had an open oil cap vs the other had a plug.
this one blows oil out through it.
any good suggestions?

 

[Scott Danforth]

you have a breather vent, not an oil cap.

if you are blowing oil thru the vent, you have a blow-by issue

do a leak-down test. most likely your rings are going

 

[glennj3]

So if I plug the oil hole up it may cause oil to blow out someplace else?
a leak down test is like a compression test? Like doing compressions on an airplane engine.
they use air compression at TDC and see where it holds.

 

[Bondo]

So if I plug the oil hole up it may cause oil to blow out someplace else?
a leak down test is like a compression test? Like doing compressions on an airplane engine.
they use air compression at TDC and see where it holds.

Ayuh,..... Correct,......

 

[glennj3]

My reason for asking is that this engine came with this breather type. My previous one was a solid plug.
This one has blown oil from day one.
maybe I need to find a plug?

 

[glennj3]

I just realized I neglected to say that it has a breather tube going to the flame arrester. So I’m thinking this is an automotive cap.
anyone have a spare cap?

 

[Scott Danforth]

nothing special about the oil cap. you can find it at any automotive store. your valve cover is a ford FE valve cover, however oil caps on I/Os have been standard on american made motors for nearly 60 years.

I would still do a leak down test.