I have a set of SSM IIIA's and I have been getting different information on how to change the oil. The oil looks great, but its the end of the season and I want the routine maitenance. obviously you fill from the bottom drain like all merc stuff. Supposedly there are 2 upper plugs. What about the transom assembly sight glass and filling??? Just seems like I get opionions versus answers. Need somone to give me the correct way. Please help! Thanks in advance.

I am assuming High Performance Merc Lube only! is it 5 quarts or more per drive??

I searched the forums. No answers to be found. A few opinions. Need help from those who know

I usually get help??

There is a vent plug on the side of the upper case and a small vent plug in the top cap. I fill until they reach the side vent then after putting the side vent back in I pull the top and fill until it comes out there. A couple pump after you replace the top plug and your good to go. The transom assembly site glass is a reference that I would only use to check level when hot. That is an expansion reservoir.

I beg to differ on the location of a "small vent plug in the top cap". There is no "top cap" on a #3A drive. There is a back cap with "ears" on it that the steering rams attach to and it has a large cap, in the center of it, that can be removed, that is lower than the small vent plug in the side of the case. I fill my #3A's, from the bottom, until it comes out the rear "large" cap on the back of the drive, then replace that cap, and continue filling until it comes out the side hole. Replace that plug and continue filling until I see fluid rising in my bottle. I replaced the stock inner transom plate quite a while ago, as it was very hard to see the level of the fluid in that small round window, and use a 1/2" alum. inner transom plate, that I made, and a 1 qt. bottle that feeds from the bottom and you can see the level of the fluid.

rmp, where did you get the resv. bottles ?

Sorry fpr the confusion. The small pipe (vent) plug I was referring to is on a #4 not the #3. I still stand by filling the drive only a few pump after lube exits the side vent. This brings the level to well above the top gear. If you fill until you see lube in your site glass it will be in the bottom of your bilge once it gets hot as the reservoir in the transom plate is not that big. The 2 quert bottles are the way to go as they are substantially larger.

Around how many quarts would fill the system if empty?

If I remember correctly, they take approx. 2.5 gallons of lube to fill.
The "natural" 1 qt. drive bottles that I used, I have in stock for $96 ea. They have 2 inserts that are 1/4"x20, that I mounted to an alum. plate and connected the bottom fitting to the stock drive hose. They work great and you can see the level of the fluid thru the bottle. The cap is vented and large enough to fill the bottle. I have never "overflowed" the bottles, in the 6 years that I have used them. Contact me if you need some great reserve bottles.
Gary