How an outboard gearbox works 

Brought a boat in that had shift issues to be repaired. After looking at the damage in the lower unit, the mechanic asked me how we shifted the boat into gear. He stated the worst thing you can do when shifting a boat from neutral to either forward or reverse is to do it slow and gently. That motion needs to be somewhat quick and deliberate so that the two metal parts mesh quickly to reduce wear on those two parts. Another thing I found out later on was shifting involving a stainless steel prop. Because a stainless steel prop weighs so much more than an aluminum prop, I was advised when shifting from reverse to forward or vice versa, to go to neutral and allow a short delay before shifting to reverse the spin of the prop. This delay in neutral was to allow the heavy stainless prop to come to a stop before reversing its spin. Hope this helps someone so they don't have to learn the hard way. Your lower unit cut away is awesome by the way. Thanks for sharing.

You are a great teacher, and the level of commitment, cutting the gearbox in this video, is 1:st class. Cheers from Stockholm, Scandinavia.

That was probably the best video I’ve ever seen showing how the driveshaft actually works on an outboard motor it really was very clear and easy to understand exactly how that worked

Best video on RU-vid explaining how outboard gearbox works , saved me loads of time and money

Man, this is gold! You are giving average chumps a chance to succeed! It was all magic inside that casing until you cut it away and explained. Beautiful in its simplicity.

What an effective teacher you are! (That’s from one teacher to another). Your videos are unique and that is why your audience is so large. Some channels post videos almost for the sake of it and viewers quickly pick up on that. Your viewers know they are going to get the real thing EVERYTIME.

You keep your audience engaged and not overwhelmed by pointless content. Thanks mate i'll be watching more.

I just wanted to add to what everyone else is saying here - Thank you!Wonderful explanation / demonstration.

I have learned SO much by watching your series. Just wanted to say thank you for all the effort you make to share your knowledge with others!

Again, great video. I had a mental image of how these gearboxes worked but the cutaway really shows nice and clearly how it's done. Nice.

I just want to let you know that I have been glued to your outboard videos the last few weeks. I bought my first boat with a 60hp Johnson on the back and you have been more than informative about my new boat. Cheers.

Your videos are so useful - many thanks. Just stripped down my old 4hp tohatsu gearbox and replaced all the seals.

the outboard motor is truly a bit of marvelous ingenuity, now more so than before viewing this video, thank you!

This is just brilliant!! I had no knowledge of how all this works, it now makes a bit more sense. Many thanks for your explanation of a very important part of the boat. Well Done!

Imagine my surprise when in my Marine Transmissions class at Broward College in Florida, USA, my professor put on YOUR video to show us a clear example of outboard marine transmissions? Been watching your videos for a few months now. You produce fantastic content!

You do the BEST job of explaining things in terms I understand and I feel much more competent to make repairs on my boat! You have taught me about trim tilts, spedo holes plugged, now about the lower drive unit! Thank you so much

Just wanted to say thanks from Northern Ireland.The video's really help. As the poor sod in a local fishing club who does the maintenance, your video's are invaluable to me.The explanation of the gearbox lower unit is great.

ABSOLUTELY FANTASTIC....best on the internet....bar none! T H A N K S !!!

Just found your site in the last coupler of weeks. Refreshing to see a hands on delivery. You have saved me a lot of heart ache. Cheers

I never took that apart when I owned an I/O and always wondered how it worked. Awesome job on the prop man. Good video.

John from Minnesota. Been watching u for quite a while always entertained. And learning more and more bout engines. That I thought I new. U make things very clear. Thanks. We here are having -20 degrees Fahrenheit. With windchill to 30to 35 below. And have 30in snow in one week wish we could enjoy some of ur weather. Without the bug s. Good work mate.

this video takes the mystery out of how the lower unit gearing works, thanks.

This is the best, by far, video to explain an outboard gearbox. Thanks Stu for the invaluable instruction you have provided over the years!

Amazing video I had my dog clutch go on the middle of the lake yesterday fml but this video is a big help thanks so much

Just discovered your channel and this is one of the best videos I've seen in a long time. I've been boating for over 40 years and love to tinker with all things marine... but usually just above the waterline. Until now I've never really been clear on just what is happening in the gear case of an outboard motor. Your commentary along with this excellent visual prop (pun intended!) makes it perfectly understandable. Well done mate. Consider me subscribed!

I have learned a tremendous amount from you and the videos that you so thoughtfully and intelligently produce. Thank you for what you do for everyone around the globe. I'll keep watching!! 👍

I found your outboard series when i started having trouble Edith my enduro 15hp. You give very useful education on the i depths of how these engines work. Thank you danger marine and cheers.

Thank you for the video. I have a Mercury Force 120 in Vancouver Canada. Never knew exactly how the gearbox worked. Appreciate you passing on the knowledge to people.

Another excellent video thanks Dangar. Love the cut-away - that really helped see how it works and now I doubly appreciate your efforts to make this video.

outstanding! Great explaination, thank you for your time mate.

Just the bearing carrier came out leaving the roller bearing at the bottom around the prop shaft . Need not worry anymore . I pulled out the shift rod then blew air through the oil fill hole and wala. That piece of metal blew out and smacked my hand so , I had a beer and a shot of Jack Daniels , gunna get pissed instead of pissed off my friend . I'm so happy , and so appreciated with your help trouble shooting .

Good stuff to see for real! I should have checked this out and got the manual before changing the impeller on my zuki. I didn't disconnect the shift rod, now I get to pull the gears out!

You are the great teacher to us part time tinkers of small engines, thanks a million.

Your videos are absolutely inspired. I love the videos and your explanations. Fantastic!

Thanks, please keep making these videos. As a newer power boat owner without a nearby mechanic or marina, your videos have helped me get a few problems sorted.

ever grateful for this tour. Education and Understanding are the fundamentals of life and your generosity in helping is to be applauded. Thank you.

One word: EXCELLENT.

Super informative. Thank you for making these videos and keep up the good work!

Great video , very informative, I’m in the process of replacing the gears and seals on my 88 mercury 100 HP outboard , water got in it and destroyed the pinion and gears , had my boat for 13 years and kept in good shape , bought most of the seals and bearings but the gears set are very expensive here in the states and kind of hard to find given the year of the motor , thank you so much Sir for all your videos , I am a fan

So much complicatedness at such great speeds/forces in such tiny spaces, it truly amazes me. Never even used an outboard engine myself but I'm in awe of these things.

Bloody hell. And all this time I figured it was just magic that goes on in the lower drive.

Very educational. Even I understood it :) Thanks.

Thank you for posting this!! I know it was posted 7 years ago, but it’s extremely helpful after all these years!

Great illustration on explaining how a lower unit gear box works, I learned something. Thank you.

good work...

Awesome video!

Thank you for being here to help teach us about outboards!!!!!!!

Simple, yet very clear - a rare gift!

You are amazing men thanks for your free lessons lol

"Crenellations" I think is the word you were searching for when talking about the dog clutch. 😄. Like the tops of English castles. 🇬🇧

Thanks for the cutout im learning more about outboard motors great video keep em coming Thanks again Chris

I an learning so much from your videos . you are a great teacher. Continue the good work. stay strong.

Thanks for all the easy to understand video for a first time outboard owner , really helpful. B O A T. break out another thousand. LOL

Well I never knew how the gear box worked, thanks

Excellent video, changing impeller just now and this lets me know what’s going on internally within the engine!

I just recently replaced the o ring and prop shaft seal on a Mariner 15 hp. Your video really helps, as its nice to see what I was dealing with.

Happened onto your channel by accident. Thought the title was DANGER Marine and thought oh this might be a bit of a laugh and clicked on it. MUCH to my surprise I found what I consider to be the BEST maintenance channel on the net. I am a licensed Airframe and Powerplant mechanic, and have a lot of maintenance and repair experience, all on aircraft--none on boats. So I was very pleased to find an INSTRUCTOR of such high caliber. You take the mystery out of the equation. Now I feel better equipped to maintain my new to me sailboat kicker engine. Thank you for such great vids! Of course I subscribed after the first one I watched. Keep up the good work.

good vids muka

Your videos are AMAZING. I like how you not only show people how to repair motors but also explain how things work.

Excellent and informative video! I was wondering how this worked. I’m working my lower unit over now, waiting on parts. Your videos helped do this myself. I’m using your ratchet strap and leaving in gear ideas from another video. Many thanks! 👍🏻

A tip as to how to operate your outboard. Our dive club bought a RIB with a 150 Johnson outboard, I'm the guy responsible for maintenance. When reverse gear was engaged, it would "jump", by that I mean it felt like it was in gear then went to neutral for a fraction of a second, then went back in gear. Eventually it lost reverse. On gearbox disassembly, it was found that the dog clutch had worn away the dogs on reverse gear. I came to the conclusion that this was due to the previous owner "easing" it in to reverse, clunk, clunk, clunk, rather than pulling the shift lever back decisively to positively engage gear. This wore down and rounded the edges of the dog on the reverse gear and eventually made it so it wouldn't engage at all. As the price of a new replacement gear wheel was rather silly, I sourced a secondhand gearbox with problems, but it had a good reverse gear, and used that to make a good unit out of two, for much less money. The lesson from this is, when engaging either forward or reverse, shift gear decisively, secondly, don't ram your gearbox into reverse to slow down unless it's an emergency and absolutely necessary. Ease off well before you have to stop, hit neutral and let the boat spend its energy, so you are virtually stopped by the time you you reach the dock, buoy, or whatever you wish to get along side, or moor to. Always operate your boat with the utmost sympathy, and it will pay you back handsomely. That doesn't mean you can't work it hard, but think ahead and don't subject it to any unnecessary strain, which could be avoided by anticipation and intelligent boat handling.

thanks for tearing into an old lower unit to explain the drive gear and dog clutching operations, helps a lot to actually see the process as I'm trying to narrow down my engine problem. Thanks mate!

Nicely done on the dog clutch in and out explanations! Good job

Thank you so much! This is the way to teach, simple, quick, easy. THANK'S

I had a hunch that this informative and educational video would be made here... And I was right. Thanks for all your great videos, you've been very helpful so often, your a true legend!

Your video saved the day when we were putting our outboard back together, Very informative. . Thanks!

One of best videos I’ve seen. Great! Thank You!

Love that cut away view! Makes it very easy to understand how an outboard shifts gears. Cool stuff!

Great help, Sir! Me and my boat co-owner are not dummies in mechanical works, but dummies in boat engines, and your videos help us a lot to understand where and how local mechanics are cheating us with services and repairs. :)

That is great Stu, I have pulled a few apart and great to see the side cutaway version. Ross

Thanks for this. Really helps to be able to actually see the inner workings. Keep it up!

Great video man I couldn’t find anything on where the oil process goes in a lower unit. Love it

This is a great explanation, for someone like me who is starting from a knowledge base of zero , it really has helped me so much. I have enjoyed your wholes series. Thanks again.

Excellent, crystal clear, and much appreciated. I have a c. 1980 Merc that's grinding a bit when shifting, and found this very useful... and a bit reassuring. Good work, mate!

Nice man, work at an insurance company where they did similar cut out the sides pulled the carrier and hooked a little electric motor to the drive gear to show it. Simplicity of these motors is pretty ingenious, seem way more complicated than they really are. A little explanation can really help people take care of their boats. Especially the dog clutch, so many think they gotta ease into gear which is terrible for it when you see how it chips the crap out of it.

Dangar, thank you so very much for taking the time to do this. very , very good video and explanation. love the way you showed how things work inside, really, really good. I have an outdrive, bravo iii and this was great to understand how it works. god bless.

Congrats on your 1 Million video

Great explanation and great narration.

Thats the best demo of that ive ever seen , cut away works perfectly.

Excellent video. More please.😊 I would like to learn all that I can about repairing & maintenance of the outboard. Thank you for sharing your knowledge with others.

I'm a new boat owner with lots to learn and this was very helpful Thank you!

Great explanation, thanks for the video

Thanks for that video and your time to film it

Thanks. Just took one apart and now I understand what moving the shifter does.

Hands down one of the best videos on RU-vid

Useful video, thank you for sharing your knowledge. Having worked on inboard engines for a number of years, I always thought outboards were the work of the devil and avoided them at all costs. Things like this are good to know. A simple, yet effective system

Well done. Love the cutaway!!

Great demo!

Just about to do the LU seals on a 1976 Merc 150hp, I now feel I understand the lower unit much better , Thanks A1 vid !

I must say yu make me so clear of how outboards work ...This is short video but I must say it really useful adding to my knowledge about outboards

Thanks Bro. Awesome illustration

20 something years of boating and I never knew how this worked . lol. thank you for all your great videos

Superb. Thank you for the explanation! It was all pfm till now.😎

Great video! Thanks for sharing.

Outstanding explanation. Thank you!

Great job explaining, very well done! Love the cut out gearbox, made it very easy to follow. Always wondered how those things worked!

Aussie guy you are a lifesaver!! This is just what I needed. Good on you mate! I hope you have a great day

SUPERB...Highly educational. Thank you.

Very nice job on the Gearbox Cut out. Thanks for all the work you put into this Video.

Clean concise and informative. Thanks mate.