Pressurized lower unit ?

[c903]

When I popped the stop (fill) screw from my lower unit, the unit was pressurized and blew a spurt of oil with some force.<br /><br />I filled the lower unit 2 weeks before test run and let the unit sit with the check hole open for at least an hour or more to allow any trapped air to escape.<br /><br />When I checked the oil level today, it was 2 days after my test run....and blown lower unit. How did the unit become pressurized? I am now thinking that if lower unit was pressurized when I was test running on lake, the oil flow might have been restricted by the pressure?????

 

[Goodoleboy]

Re: Pressurized lower unit ?

Its near to imposible to fill a lower unit from the top hole. The 80/90 weight oil is so thick that traped air can not escape, theirfore giveing false indication that it is full.<br /><br />It must be forced in by pump from bottom drain hole . When oil runs out the top hole then replace top screw. Vacum will hold oil in gear case when pump is removed from bottom screw hole. Then replace bottom screw.<br /><br />If you have electric shift then it uses ATF fluid. Not 80/90 gear oil.<br /><br />Good luck!

 

[Cricket Too]

Re: Pressurized lower unit ?

I have heard this a lot and seen it on this post a lot too, and even though it is the correct way to do it, I have never had the vacuum hold the oil in, as soon as I pull the pump from the bottom I get a gusher from the hole. How do you hold it in?

 

[BoatBuoy]

Re: Pressurized lower unit ?

Put in the top screw before removing the pump (or fill bottle). Then remove the pump. Depending on how fast you are, a little will escape as you put in the bottom screw, but not enough to make any difference.

 

[lark2004]

Re: Pressurized lower unit ?

If you have electric shift then it uses ATF fluid. Not 80/90 gear oil.<br />

If you want an electric shift gearcase to keep working, then use BRP Premium Blend oil.<br /><br />but this all off track a bit. <br /><br />What does the oil look like that comes out of the gearcase? is it milky?

 

[ddbyrd3]

Re: Pressurized lower unit ?

The 2 main reasons, I have seen gear cases pressurize, is either due to old cracked fill and drain plug O rings, or the prop housing O ring and shaft seals.<br /><br />You should use your fill / drain O rings ONCE them toss em and replace em with new. (or the nylon replacements)

 

[umblecumbuz]

Re: Pressurized lower unit ?

And no, the oil flow won't have been restricted by the pressure. It will still circulate normally by the rotation of the gears.

 

[c903]

Re: Pressurized lower unit ?

Lark:<br /><br />The oil was clean. No water.