How To Change your Boat's Lower Unit Oil

[@mscarbo24]

you should always pump your gear oil in slowly till it comes out the top hole, then let it set ( with pump still attached ) for a few mins. to get the air bubbles out. then top off and add screws back in. just how i was taught.

[@jdutube1414]

Simple and straight to the point, good job!

[@KozarBen]

I always remove upper first, then put it back in loosely, then remove lower, not a good idea to drain the oil until you are sure you can get the top open to put fresh oil in, it's a bigger deal on car differentials but still good practice, ;). Nothing sucks like draining the oil then figuring out you can't refill it!

[@tmgltd2994]

But you fill from bottom so no air bubbles

[@Belzer21]

Bought a boat from someone who never did a lot of maintenance. It’s a pontoon with a 97 Mercury. I decided to do this and the oil that came out looked like chocolate syrup and stunk so bad, it smelled like rotting meat. Unbelievable. This is something easy to do and doesn’t take a lot of time.

[@iroc2019]

Hello what about the upper part of the engine - pistons. Does this oil cover that as well.

[@euanward8100]

No the lower unit is isolated from the rest of the motor.

[@martinschulz9381]

I'm about to do my first lower end change on my Suzuki. I guess it surprises me that the outboard companies haven't figured out a way to design the bottom end so that the oil can be filled from the top hole like every other gear box.

[@davidmartins6566]

Appreciate you making this video. I'm going to change mine now.

[@goosenation3210]

can you drain the oil before winter and then fill it back up after winter

[@boatsdotcom]

That's not the best move, Goose. You want the oil filled to the top to displace as much air as possible. Otherwise, condensation may form in there.

[@goosenation3210]

Thank you

[@tmgltd2994]

What about the little gasket/seals?

[@notblazedfordays9536]

What about them? They typically come out on/with the screws…

[@metisrick5946]

Great video but missed the "make sure your gaskets are good" component.

[@lynnmaureenshevshenko8254]

yeah that's very importante', do like on a car oil pan, change the o ring every time, unless you forgot to get a new one, lol

[@tylerandtony2]

You have any suggestions on gear oil leaking? Small amount, but it's leaking. I am not a boat mechanic, obviously, but this video, is this for gear oil?

[@boatsdotcom]

If your gear oil is leaking, take the boat to your friendly local dealer or marine mechanic - immediately. When oil leaks out water gets in, and the result is catastrophic lower unit failure.

[@tylerandtony2]

Thanks. Right now we have to do a once over and check everything out before putting her back in the water. She was abused the past 3yrs. =( We had sold her 3yrs ago and she went through 3 other owners until I found her again, two states away, and I bought her back. =)

[@boatsdotcom]

Heidi Martin what a journey! Glad she's back in your care.

[@ediipooh1991]

***** how do I know if the gear oil is leaking?

[@boatsdotcom]

ediipooh1991 If the boat's on land, the clearest indication is oil on the ground under the lower unit. If it's in the water, look for a consistent, unexplained oil sheen that appears whenever you lower the engine.

[@dimseeida]

Both upper and lower oil plugs are blocked and I can't unscrew them. Any advise?

[@TheIndianscout]

dimseeida try heating the screws up with a heat gun to help loosen them

[@Rudy32225]

Impact tool and hammer; when that didn't work 1/2 drive breaker bar with large flat screw fitting. Leverage usually works.

[@haydenh4278]

Suffer

[@psychodad4634]

I have a Johnson 150 2 stroke and so far, I have only found one plug for the lower unit. Is the procedure the same?

[@boatsdotcom]

+N2WIN N2WIN What's throwing you may be the location of the top screw plug. On the older 150's it's located way up high, above the forward section of the anti-ventilation plate, starboard side, right where the fin begins to protrude from the side of the lower unit. Check there, and see if you don't find it.

[@psychodad4634]

+boats.com Thank you for the tip. I found it this morning. Thank you.

[@touu]

My magnetic drain screw at the bottom of the motor is stuck. Any advice on how I can remove it? Also, where can I purchase a new drain plug? It is a 1996 two stroke dt40.

[@boatsdotcom]

+touu Ouch, that is a major problem. An impact driver may help but if you can't get the screw moving you really should take the engine in to a certified marine mechanic, before you strip the head. In the long run, it may need to be drilled out - a job for a pro, for sure. As far as finding a new plug goes, Google will be your best friend but usually you can find what you need at marineengine.com or wholesalemarine.com.

[@Rudy32225]

Had same problem, finally half inch drive breaker bar with large flat screw socket did it.

[@ortega2424]

Could you thread the lower nut in and fill from the top?

[@mt2020]

no you might leave air in the lower unit

[@mt2020]

did not talk about changing the o-ring on the plugs

[@notblazedfordays9536]

What do you need to know. If one is bad, you remove it and put a new one on… are you really that braindead 💀 😆

[@jimquantic]

Thanks for posting, but I am wondering, why not after draining, just screw back in the bottom screw, then fill it up until the oil starts to run back out of the top hole, slightly, then cap the top hole at that point?

[@boatsdotcom]

Jmichal - sorry it took so long, we missed this one for a bit! That doesn't work well because there's no air flow - the air needs to get out while the oil goes in.

[@jimquantic]

Yes, that makes sense, oil filler hole so small, oil so thick. And I would imagine? that if you tried to put it in, from the top, via a tube, it would be nye on impossible to find a piece of tubing small enough to leave an air gap, yet large enough to allow the heavy fluid to travel through it. I get it, thanks.

[@abaroun3648]

should i change the plug seals or keep the old ones ?

[@boatsdotcom]

Hi a Baroun. Check the engine's owner's manual to be sure, but in most cases yes, the seal on the screw should be replaced every time the screw is removed and reinserted.

[@MattsShop]

You should always change the seals every time you change the oil, especially if you have the fiber ones. They get really damaged when you tighten the screw. If you have the nylon/plastic ones they are normally good for a couple of times.

[@kevinblanchard611]

New gasket every few years too! Thanks

[@CindyDaisyPeanut]

Very Good Video ! Thank You Sir

[@johnechterhoff4791]

Is it possible to replace the plugs with (of course) with the same sized threaded type only a type that s removed and replaced using a socket wrench? I had a Evinrude 175 back in '88 and changed the gear lube with a big flat blade screw-driver and it tightened down fine. Six months of heavy fishing later, I went to loosen the screws and I could not. I want to say impossible. I suppose the vibration from the running motor tightened it into oblivia! LOL! A socket would have done it! Thanks for the good vid! JEE.

[@boatsdotcom]

Hi John Echterhoff. Afraid not - one of the reasons the plugs are recessed screws it to maintain the lower unit's hydrodynamics. A socket would require a protruding head and/or a larger recess, both of which would create turbulence. These screws do often become difficult to remove, but often the problem is due to someone using an under-sized screwdriver for the task. Usually, if you use the largest screwdriver with the largest head possible, you can break it free without a problem.

[@johnechterhoff4791]

Thank you very much!

[@boatsdotcom]

John Echterhoff Glad to help!

[@reallyhappenings5597]

In that case, is anti-seize recommended for these drain/fill screws?

[@psychodad4634]

Me again. I have my motor down from warming up the engine. I see oil coming out of the back of the lower unit. Should I drain it and take it apart to see what is causing the oil leak? Secondly, if it's a seal, where can I get it from locally or online?

[@boatsdotcom]

+N2WIN N2WIN EEK, that is officially BAD! Yes, you're probably going to need to replace the seal (pray that's the problem, or you have more significant damage to tangle with). If you Google the engine model, year, and "prop seal," you'll have no problem finding one.

[@Nate......]

Can you believe there's people out there with 7 &10 and even 20 minutes of a video showing how to change the lower unit oil. Their video is longer than how long it takes you to change the oil 🥴

[@officialWWM]

Why wouldn't you just fill it from the top?

[@devinstone7229]

@revenge69ful same way, it over flows (just don't use the pump) just like the diff in a truck. i really don't understand why you would get a pump and try to put a drain plug in after you filled it.

[@devinstone7229]

@revenge69ful lol u must be a computer desk employee.

[@devinstone7229]

@revenge69ful also can you read?

[@officialWWM]

Phillyfishguy jeez, the only know it all arsehole I see here is you!

[@officialWWM]

stimmo77 that's not the point, lol.

[@MeadowsJames]

Thanks for sharing!

[@kelvinyoung3303]

Mine don't have a plug on bottom

[@NewYorkMudBoggers]

Why can't you just put the oil in from the top plug?

[@devinstone7229]

i don get it either, and i see no reason not to. maybe air pockets but then id just say trim the motor hard and back then recheck, maybe even check one last time after you run her. either way gauge how much came out and how much went it in if ur really ocd

[@bigblocksbigturbos853]

Phillyfishguy I could see that being an issue in a unit that has not been run in a long time and the water and oil has separated, then pushing the oil in from the bottom makes sense to force the water out but if you have ran the motor and had the lower unit in gear more recently than a year or more then the oil you just drained out would be milky and right there you would know that you have a seal failure somewhere that needs to be repaired right?

[@manjirasaraekanayakaalphys9256]

Can we call this as a motor boat?

[@samalfakir5463]

you forgot to purge the bubbles out ...

[@jdeb0016]

Thanks!

[@alpha1towing570]

u cant cause the trapped air wont allow the oil in

[@marzukhinmuhammadaking9925]

now i know ! :)

[@daneluta]

Gloves...

[@lynnmaureenshevshenko8254]

yeah, right? protect the environment? of course but also protect your hands!

[@klassy75]

If you want to truely keep the oil out of the environment, you would change it on impervious surface like concrete. Why are you on grass?

[@lynnmaureenshevshenko8254]

cardboard under everything 4 foot square should do it

[@johnechterhoff4791]

Is it possible to replace the plugs with (of course) with the same sized threaded type only a type that s removed and replaced using a socket wrench? I had a Evinrude 175 back in '88 and changed the gear lube with a big flat blade screw-driver and it tightened down fine. Six months of heavy fishing later, I went to loosen the screws and I could not. I want to say impossible. I suppose the vibration from the running motor tightened it into oblivia! LOL! A socket would have done it! Thanks for the good vid! JEE.

[@piercemajette]

Sounds like your motor had an electrical issue and the bolt got zinc’d. A little grease goes a long way!