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I'm going to try to replacing the lower unit seals on my 1998 Yamaha 90 / 2 stroke myself for the first time and looking for any advice people are willing to share. I did the upper seal last year when I did the water pump and that was easy but they say the lower / prop shaft seal is difficult to remove. From the research I've done so far, it sounds like the "proper way" to do the job is to completely remove the gear case and shafts which they say is fairly complex if you're not a mechanic like me....

So, I found this series of Youtube video's where the guy is able to get the seal out by drilling and tapping the seal with a screw and then pulling them out with a slide hammer. I don't see much about this method on the web so my main question is - is this a viable approach or should I just take my time and do it the "proper way"?

The parts to do the job are only about $50 and I'm ordering the shop manual which I'm sure will describe the "proper way" but this look a lot easier. It seems I need to do this job every few years and if I can save the $300 and 3 hours driving my boat to and fro the shop I figure I'll be way ahead of the game as long as I don't screw it up too bad.

Youtube part 1 - http://youtu.be/VZzwLU07v8U
Youtube part 2 - https://www.youtube.com/watch?v=JdlcX...dlcXBxy_VY (fixed part 2 link)
Youtube part 3 - http://youtu.be/xcxDyObTqfU

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Not too bad of a job. Here is an example of a rebuild on a Tohatsu lower unit: http://www.whalercentral.com/userphot...lbum_id=67

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Thanks wlagarde. Reading the shop manual last night they outlined a long list of special tools needed if performing the full tear down as you did. I'm planning to buy a slide hammer and gear puller with various adapters but aside from those, were there any other "must have" tools needed for the job that an average back yard mechanic like me wouldn't already have laying around?

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Bob,
I have pulled any number of gears and seals. If any of them become impossible sacrifice the part easiest to replace (usually the replacement part in hand) and protect the casings and shafts. Don't force, sometimes the turn or twist is opposite of what you think or a hidden snap ring.

A good snap ring tool is nice to have. If you can do a lower unit you would have the skills for a hydraulic cylinder.

wlagarde, meticulous work. Thanks for the photos and sharing.

Garris

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Thanks Garris, so it sounds like your also a proponent of the full year down also? Up until now the biggest job I tackled was the carbs but this looks like an order of magnitude more of a challenge. I used to pay for service on everything including numerous fishing reels etc but I'm gaining knowledge and more confidence with each project.

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Bob,
I tip my hat to you. I would not tackle a carburetor. Twisting screws and dialing in fuel is something I messed up in the past. Some talented fellows would say "...running lean..." or "... you have a miss..." and with my hearing it would sound fine to me.

I am not a proponent of a full year down. I worked the boat running for some time to know how I wanted to dial it in. I just started projects that mushroomed. Ended up a year down for "...an ounce of prevention...". I am extremely cautious with the boat because others are depending on me for safety.

Take your time with the lower end. It is mechanical and will come apart. If something is locked, back off and think. Sometimes a good whack, sometimes post and ask questions. You will do just fine.

Garris

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Bob - No special tools required other than what others have already mentioned. The special tools (backlash tool, shim kit, etc) are needed only if you begin to replace parts that would affect the alignment of the gears. You would be just fine replacing the seals but full disassembly will allow you to inspect everything so you know without any question whether there are lower unit issues that need to be dealt with.

Garris - Thanks for the compliment

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The carb rebuild was tedious but nothing to difficult. I bought the rebuild kit that includes all the gaskets, rings, bowl, jets, etc. but there wasn't anything to adjust (that I know of)... I just put everything back the way it was, took my time, and kept careful track of everything by taking pictures. What a joy when it started on the first try.
I figured if I botched the carb job the worst I'd do is the engine wouldn't start, obviously tearing down the lower unit improperly could really fowl things up.