Changing Lower Unit or Sterndrive Oil On A Boat | BoatUS

Not only do you need to change the oil in your boat engine, you also need to change the oil lubricant in your boat's lower unit or sterndrive. BoatUS Magazine contributing editor Charles Fort walks you through this simple procedure of changing sterndrive oil on a Mercruiser Alpha outdrive, which will keep your boat's engine running smoothly and help avoid a tow. You'll not only learn the simple procedure that will save you lots of money, but you'll learn a couple handy tips for keeping it clean. Learn more about outdrives and sterndrive maintenance at www.boatus.com... and www.boatus.com...
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[@johnwinterburn2669]

First Class How-To video. Straight and to the point, no fluff, no useless commentary. Real teaching. I changed the gear lube in my stern drive after watching this and it was all accurate information that made the change so much easier than I imagined. Thanks again! Keep them coming!

[@boatus]

Wow, John!! We're blushing. Thanks so much for watching and letting us know that it helped you. Here's to a safe, fun, and incident-free boating season!

[@flowers3871]

Hi thanks for the good video I learn and I will doit my self now , I have a question what about the oil reservoir on top of engine is that for stern drive will that empty when u drain the oil? Or can u add oil from there , am not sure what can u do from there , all I know is for the stern drive .

[@jpete3027666]

Great video. New boat owner and just did this on it. Simple!

[@boatus]

Congrats on the new boat, John! Thanks for watching

[@1973deepee]

Another excellent video!! I'm so pleased you decided to do this. Much better than other videos I've seen on the same procedure. Well planned and executed.

[@boatus]

Thanks! Stay tuned for more new videos we'll be putting out in the next few months.

[@davenedo]

What type of oil needs to be used

[@wavealip8059]

Great video for newbies.

[@boatus]

Thanks, Waveali P! If you haven't already, make sure to subscribe to our channel for notification when our new videos are posted. We have a great series coming up on four-stroke outboard maintenance.

[@rebman5150]

Subscribed. Great videos. Thank you.

[@boatus]

Thanks for watching and subscribing, Richie! Glad to have you onboard.

[@prapra15777]

Great video. One question: Do I have to put grease on the screw before I put them back in? One guy told me to put light bulb grease on the screws o ring to prevent water from getting into the sterndrive

[@boatus]

Thanks for the question, Phil. We've never heard of using lightbulb grease, but yes, a dab of marine grease or anti-seize is in order for any screw or bolt being used near or below the waterline.

[@GenYShyGuy]

Only thing I would change, is always undo the vent plug before the drain. What if you drain the oil and the vent screw is seized in? You can’t get it out, you can’t fill the oil. Headache can be avoided by undoing the vent screw first.

[@boatus]

Good suggestion. Thanks, Chris!

[@AchikSarih]

Merci beaucoup ❤❤❤❤❤

[@boatus]

You are very welcome. Thank you for watching.

[@baileyfaust179]

Can i just fill through the vent hole with the bottom plug in until it comes out the top?

[@boatus]

Thanks for the question, Bailey. If only that were possible! The problem with that is the oil is displacing air, so if you try to pump it in from the top with the bottom hole plugged, the air has nowhere to escape. The oil would just keep "burping" out the top. When you pump it in from the bottom with the top vent open, the air has a way to escape as the oil takes its place in the lower unit. Hope this is helpful!

[@El.KompaLalo1850]

Can i add regular 75W90 gear oil on the stern drive instead of marine gear oil

[@boatus]

Thanks for your question. Albert. Most marine gear oil is single grade, typically 90 weight, not a multi-grade of the type that you mention. We always recommend using only the oil specified by the manufacturer. You may pay a little more, but it’s far cheaper than having to replace the stern drive. Also, if you use a different oil than specified by the manufacturer, you’ll more than likely void any factory warranty that you have on the motor and/or outdrive.

[@danielrabines9201]

Soooo.. I see a bunch of these videos being done from land. What's the best way to do it while my boat is on a boat lift over water ....

[@boatus]

Great question, Daniel. The best way to change the oil in a lift-kept boat is to pull the boat and do it over dry land. Otherwise, the possibility of spilling oil directly into the water is very significant (and comes at a high price). There are a few outfits that specialize in doing oil changes on boats in lifts over the water, but they have unique gear and know-how specific to the task. They also tend to be located only in high boating density areas where there are lots of lifts and can't be found in many parts of the nation. If you can't hire a professional to do the job we'd never, ever recommend attempting an oil change while the boat's in a lift.

[@Capucee]

Where do i find the fill screw ? And what is it called ?

[@boatus]

Thanks for your question. It all depends on your particular outboard or sterndrive, Canada. Best option (since we're not there in person) is to do an online search for your particular model and download the owner’s manual. It should give you all the info you need, including the manufacturer’s specific service recommendations.

[@Jonhawblitz]

Can I top off the through the dipstick hole if need be?

[@boatus]

Thanks for the question, Jonathan. In a word: No. Pouring oil down the dipstick tube will add oil to the engine crankcase, not the lower unit. You have to remove the upper and lower screw plugs and pump oil into the bottom hole until it comes out the top hole. Then replace both screw plugs.

[@elitebowman5386]

how much oil does the stern drive Mercruiser take? I have a friends motor lower unit he asked me to put oil in. He already drained the oil. I bought CRC Marine Hypoid 90 Lower unit oil and put 2 tubes in plus had little more, so like 20 plus ounces and wasn't enough. Any help would be appreciated so I can have an idea how much more oil I need. Thanks

[@boatus]

Thanks for the question, Elite. You do not say which drive (Alpha 1, Bravo3, etc.) you have, so I can only give general guidance. Some outdrives have an oil reservoir on the inside of the boat in the engine compartment - often adjacent to the transom. In this case it will need to be emptied and refilled. After opening the engine hood, remove the plastic reservoir tank - it normally slides into an aluminum bracket and is easily removed. Unscrew the cap and empty the oil into a suitable container for later recycling. If there is sludge in the bottom of the tank, this should be wiped out with clean rags so the tank is perfectly clean. Replace the empty tank leaving the cap off. Fill the drive leg with fresh oil as shown in the video, although it sounds as though you have done this. After replacing the vent and drain screws in the leg top up the reservoir tank until it is at the full mark. Hope this helps, and thanks for watching!

[@elitebowman5386]

@@boatus . Thank you for the reply. It is a friends boat, so not sure which drive it is. I put CRC Marine Hypoid 90 Lower unit oil in it not the Quick Silver brand. It says for stern drive motors too.Is that ok to use that type of oil? It says it is for them too. I will have to go see if it has a reservoir under the hood. Thank you for the reply.

[@boatus]

@@elitebowman5386 Unfortunately, without knowing which drive it is or being there in person, we can't really answer with any confidence. We always suggest using the type and amount of oil recommended by the manufacturer, the specifications for which can be found in the owner’s manual. If the manual does not exist - not an unusual occurrence - the relevant information can often be found on the manufacturer's website.

[@elitebowman5386]

@@boatus Ok, thank you for taking the time to reply.

[@DunbarIII]

Any way to check the oil level in the 1st gen ?

[@boatus]

Hey Dunbar. Thanks for the question. Simple: Pull the top screw, and the oil should be right up to that level. It's a small hole, so it can be helpful to have a flashlight handy to shine in there and see what level the oil's at. Hope this helps, and thanks for watching.

[@ryancorse8793]

I was curious about the gear lube container up under my engine hatch. My mercy has a container. Can i follow this video for my boat or do i need to do something different? Please and thank you

[@boatus]

Thanks for the question, Ryan. I am not sure I understand what you are asking. It sounds as though you have an I/O engine and drive unit. As far as I am aware, the only oil containers underneath the engine hood for those type of installations is the for the power steering or the trim and tilt. However, some Mercruiser units have a gear lube monitor tank. On Bravo outdrive units (which is most likely what you have) you still have to drain and refill the lower unit as shown in the video. If you can be a little more specific, then we can give you accurate advice as it relates to your particular boat.

[@RadioClik]

Do you know where can l find the hours on a see ray185 1997 ? Thanks

[@boatus]

Thanks for the question, Radio Clik. This boat was offered with various engines, with the 4.3liter Mercruiser the most popular option. Basically, this was a carbureted engine and has no ECM (electronic control module) from which the engine hours, with the right computer software, can be read accurately. Unless there is an engine-hour meter on the boat then I am afraid that there is no accurate way to measure the hours, and you will have to rely on service records if these exist, to give at least some idea as to how often the engine has been serviced.

[@RadioClik]

@@boatus thank you very much

[@jpraba3490]

I might have missed it...... the gear oil reservoir needs to be topped off as well.

[@boatus]

I’m not exactly sure what you mean when you say the "gear oil reservoir." Draining the oil entails removing the lower drain screw and then removing the top screw to let the air in so that the oil will drain correctly. Once all the oil is drained, new oil is pumped into the bottom hole until it starts to weep from the top hole. The top screw is then replaced followed by the bottom screw. That’s basically it. There is no other reservoir in the lower unit. Some Mercruiser sterndrive units have a reservoir in the engine compartment, but these are comparatively rare. Let me know if I'm misunderstanding.

[@jpraba3490]

@@boatus I was referencing the Mercruiser reservoir in the engine compartment. Just an FYI and reminder for those who do actually have it. Great informative videos!!! Thanks for taking the time to produce and respond to comments!

[@boatus]

@@jpraba3490 Thanks for the reminder, JP!

[@patrickflynn3036]

@@jpraba3490 To fill up the reservoir, do you just keep pumping the oil after you close up the top vent and then it will eventually end up in the reservoir?

[@paulplasma1]

@@boatus I am wondering the same thing as @Patrick Flynn, To fill up the reservoir, do you just keep pumping the oil after you close up the top vent and then it will eventually flow up into the reservoir????

[@richardlavoie6833]

The sterndrive should be at level.

[@boatus]

Thanks for the comment, Richard. Not sure what you mean by "level." It should always be in the down position as seen here - never in the raised position.

[@michaelandrews934]

Based on physics, down and not level would make the most sense, making the drain hole the lowest point.

[@E12_Sterling]

Incomplete procedure. Did not address the drive lub monitor, drainage and refilling which is part of the mercruiser maintenance procedure. Also did not address oil spec.