Why fill an outdrive from the Bottom?

[cmyers_uk]

I have a Volvo Penta SX-M drive and when replacing the Gear oil it says fill from the bottom. Now I find it much easier to fill from the top dipstick hole. Clearly there is a reason to fill from the bottom but what is it?<br /><br />Curiosity killed the cat they say but in my case it may bust the outdrive!<br /><br />Regards<br /><br />Chris

 

[lawyertob]

Re: Why fill an outdrive from the Bottom?

Chris,<br /><br />I am just slumming over her in I/O country, but as I understand it you fill from the bottom and it pushes the air out the top. It is less likely to get bubbles in the oil that way.<br /><br />Just my $0.02 worth,<br />Joe

 

[waterone1@aol.com]

Re: Why fill an outdrive from the Bottom?

There is not any kind of oil pump in your outdrive. What that means is that all gears have to be surrounded or soaked in oil or gear lube.<br />When things are working properly, your drive is sealed from the outside world. It cannot be left to gravity to place the lube, it has to be in all nooks and cranny's. In other words, there is no place for air pockets, gear lube has to get everywhere. The only way to do that is to fill from the bottom, and displace all air, untill gear lube runs out the very top of the drive.

 

[WillyBWright]

Re: Why fill an outdrive from the Bottom?

You don't really want to remove ALL of the air. But the only air you want in there is a small pocket right at the top. The lube needs some room to expand and contract or you'll blow seals. If you fill from the top, you get lots of air pockets all the way down that won't go away until the motor is running. Then the oil settles to the bottom and air rises to the top. That's usually enough air to leave nothing in the upper part of the drive. That has cooked a lot of upper gearcases.

 

[cmyers_uk]

Re: Why fill an outdrive from the Bottom?

Thank you I now understand the importance of doing it the 'Correct' way. I guess this afternoon it will be draining the new oil out and pumping new in from the bottom. <br /><br />Thankyou to all.<br /><br />Chris

 

[ahein]

Re: Why fill an outdrive from the Bottom?

I have a VP AQ-275 outdrive and both of my manuals (Seloc & Clymers) say to fill it with engine oil from a plugged hole located near the top of the drive. It also cautions that filling the drive is a slow process because it takes time for the air to escape. It also says when draining the drive oil to remove the dipstick to allow the oil to flow faster.

 

[MrBill]

Re: Why fill an outdrive from the Bottom?

If you use a magnetic tipped lower drain plug you'll also be able to keep an eye on the amount of wear you're experiencing. It will collect all the metal grindings...don't get too alarmed...a small amount each year is normal. A large amount can serve as an early warning signal.

 

[mkast]

Re: Why fill an outdrive from the Bottom?

The reason you fill from the bottom is the clearances at the bearings are close enough that the heavy viscosity gear lube will create an occlusive seal at the bearings and preventing the lube from flowing to the bottom of the gear case. In short, half of a quart, your full.

 

[Don S]

Re: Why fill an outdrive from the Bottom?

Originally posted by ahein:<br /> I have a VP AQ-275 outdrive and both of my manuals (Seloc & Clymers) say to fill it with engine oil from a plugged hole located near the top of the drive. It also cautions that filling the drive is a slow process because it takes time for the air to escape. It also says when draining the drive oil to remove the dipstick to allow the oil to flow faster.

The older Volvo drives have a large tube that connects the upper, intermediate, and lower gear housing that will let air pass, that is why you can fill your 275, or even a 270, 280 or 290 from that upper hole. But it can't be done like that on the SX style, or Mercruisers, or OMC, or you would have a very large air bubble preventing oil to get to the lower unit.

 

[cobra 3.0]

Re: Why fill an outdrive from the Bottom?

After filling, the following day I will verify the oil level again because it sometimes still settles further.