How do I add oil to lower unit

[Outboard]

On a 25hp bigfoot 4 stroke, I find only one plug screw very low on the barrel of the lower unit. I am used to other brand engines where there is an upper plug screw and the lower. I usually screw in my pump to the lower, fill with oil until it pours from the top screw hole, replace the upper screw when full and insert the lower screw to be all done. How is it accomplished with only one lower screw?

I ordered manuals but they won't arrive until Monday, Does anyone know the trick?

 

[emckelvy]

Re: How do I add oil to lower unit

There should be a vent plug on the forward Starboard side of the gearcase, above the anti-ventilation plate (aka incorrectly as the anti-cavitation plate).

If it's not in that location, go to http://www.mercurypartsexpress.com or http://www.dougrussell.com/partscatalog/collections/index.cfm?fuseaction=collectdetails&colid=01

and plug in your serial number. Then you can look at their online parts diagrams and perhaps find the plug by its description.

Not knowing your ser #, but looking at the 25HP 4-stroke gearcase/driveshaft diagrams at the Doug Russell site, I'd think that parts 4 & 5 (plug and gasket, respectively) are what you're looking for. 6 & 7 being drain plug and gskt.

HTH........ed

 

[Outboard]

Re: How do I add oil to lower unit

I think you may well be right, then the question is if you should fill to the top as with other motors? Now that the unit is open, I am going to test by pouring a little oil in the top and see if it come out where it should. The doug russell site is new to me, Thanks.

 

[Outboard]

Re: How do I add oil to lower unit

INDEED you were right, thanks. I am going to fill until it spills, this is what has been recommended on other engines I have owned, can't imagine why this would be different. The marking around the top plug hole was marked VENT, go figure.

Thanks again Chief Petty Officer