Changing gear drive oil

[Chipster27]

I'm almost embarrassed to ask what I feel is an incredibly stupid question....
I'm going to change the gear oil on my 300s. I read the manual and understand I have to open the top vent screw and the bottom drain plug (behind the prop) to drain the oil.
On the re-fill, the manual makes it sound like the oil is refilled from the drain plug and pumped/pushed in through the drain hole...is that true??? I bought a pump to pump the oil in, but I would have thought it would be pumped in to the top vent plug to gravity could pull it down to through the case, not pumped in from the bottom drain plug. :confused:
See why this question sounds dumb....:eek:

[Havasu Carrera]

Dude! thats gotta be the dumbest question ever!!:D I can not believe you asked it!.:D Only thing I can figure is that the oil is pumped in from the bottom till it spills out the top plug like a man.transmission?Ok I'm cought. I DONT KNOW EITHER. I will be waiting for the reply to and btw is it the same deal on the 225 v-6?? Thanks guys!

[Mr. C]

Don't have my manual with me but on my merc. you fill from the drain hole until oil comes out the vent hole. then let about an ounce drain out for expansion. tighten plugs and good to go.

[DCBDaytona]

Don't have my manual with me but on my merc. you fill from the drain hole until oil comes out the vent hole. then let about an ounce drain out for expansion. tighten plugs and good to go.
Correct. Make sure to replace the gaskets (little blue ones) on both the plug and vent hole screws.

[Chipster27]

Thanks guys! Seemed like a dumb question and the manual doesn't say anything about expansion :jawdrop: I course I would have lost an ounce just fumbleing with the installation of the drain plug!
I pulled the vent plug yesterday and the oil that flowed out didn't appear to be contaminated, but I've put about 10 hours on the motors and used them on 3-4 trips so I figure I should change the oil now.
Next project will be to inspect the impellers..I have an exploded (?) view of the LU and have read on HB how to check/replace them, but am reluctant to do it in the middle of the season in case I screw something up!
ANyone have any idea how heavy the LU is? Is this a one man job or should I enlist the help of a friend?

[Tom Brown]

ANyone have any idea how heavy the LU is? Is this a one man job or should I enlist the help of a friend?
I've done it myself plenty of times with the lighter 2.5 lower unit but it's not easy and it's a lot easier if you have someone to hold it in place while you align the shift-shaft. Get someone to give you a hand.

[Havasu Daytona]

You are definately going to need a friend to help you reinsert the lower unit. The second person may even need to assist with a very quick crank of the engine (don't let it start) to reset the shaft spline alighment. Be very careful.
If I were you. I would take the lower unit off and take it to Lou Colvert at Bob's Outboard shop in Havasu on Commander Drive. Have Lou replace the water impeller and shift seal since this will make it a complete lower unit service. He also has a retro-fit kit for grease seal issue on the 300's. Lou's kit works without the usual puke tank arrangement that Lakeland Marine does.
Lou is an expert on Merc outboards.
Remember if you mess up... a Sportmaster Lower Unit is over $2.500.00 to replace. Having a trained Mercury Platinum Master mechanic look it over is cheap insurance.
Warmer summer Havasu water temps are on their way. You don't want your lower unit to go BOOM in the middle of summer.

[Chipster27]

Thanks everyone!

[Xlration Marine]

Yea thats it. I bought a pump from westmarine, like 8 bucks. When she comes out the top put in the plug. Then you take out the bottom fill hose and replace the other plug. You will lose a couple of drops, it's no big deal. Make sure you use some new O rings or gaskets what ever you want to call them. Make sure they seet properly and don't tear or bind. This could let water in the lower if your not careful.
http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/91936/0/0/ooil%20pump/All_2/mode+matchallpartial/0/0

[LuckyStrike]

You are definately going to need a friend to help you reinsert the lower unit. The second person may even need to assist with a very quick crank of the engine (don't let it start) to reset the shaft spline alighment. Be very careful.
If I were you. I would take the lower unit off and take it to Lou Colvert at Bob's Outboard shop in Havasu on Commander Drive. Have Lou replace the water impeller and shift seal since this will make it a complete lower unit service. He also has a retro-fit kit for grease seal issue on the 300's. Lou's kit works without the usual puke tank arrangement that Lakeland Marine does.
Lou is an expert on Merc outboards.
Remember if you mess up... a Sportmaster Lower Unit is over $2.500.00 to replace. Having a trained Mercury Platinum Master mechanic look it over is cheap insurance.
Warmer summer Havasu water temps are on their way. You don't want your lower unit to go BOOM in the middle of summer.
Whats Up..Are You Guys Coming Over This WeekEnd???
AJ

[Forkin' Crazy]

You fill from the bottom so the air will get out. With that thick of an oil, it would take it forever to drain down and the air to get out.
I've done all my gear cases myself. Just put it in forward and leave it there until you put it back on. If it won't go, don't bump the starter, just turn the flywheel, or if you can't reach it, turn the propshaft (still in forward) until the driveshaft splines line up.
I like factory impellers. Make sure you replace all the "O" rings in the pump housing as already mentioned.
I also put a bit of grease on the impeller or housing, Seems to help it go on to the pump easier.

[Tom Brown]

I've done all my gear cases myself.
You should have Bob's Machine change your gear oil. For what he charges in parts and labor, it's not worth bothering with.

[Forkin' Crazy]

You should have Bob's Machine change your gear oil. For what he charges in parts and labor, it's not worth bothering with.
No doubt, shipping would be just chump change!!! :D