Lower Unit 1993 Yamaha 15hp WON'T come off

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Ay AY AY!



This was a very nice Saturday afternoon until a couple of hours ago,
and then I very stupidly decided to have a look at that outboard
which my dear 15 yr. old son managed to f*** up last year.

He was on a classmate's little boat last fall, enjoying himself out in the bay, and steering.

Completely out of the blue they hit rock... well when I say completely I mean if you don't pay any attention whatsoever to the big iron bar which marks this rock, which he didn't.




So I felt it was our responsibility to fix this, and I called the other boy's dad and asked to do so. The damn thing has since been lying on our garage floor all winter, and now boat season is again approaching and I need to fix it.

The rubber sleeve inside the propeller was too old and hard, and it did not give when they ran aground. Something else broke, something further up.

The lower unit on this motor has never been taken off since it was new in 1993, which was apparent from appearance of the joint between the lower and upper.

I took off the four lower unit bolts, disconnected the gear shaft, took off the anode and filter cover and checked that no other screws/bolt lay above them.


Then I began the long process of whacking the lower unit downwards with a rubber mallet. I did so for the better part of two hours resulting in a 4mm gap opening up, but no more.

No matter how hard I whack it! I did it with determination!



What is going on here? Is there something further up that is broken or corroded and won't then release?

I would greatly appreciate any advice.

 

Loosen the nuts holding the lower unit on, leave about a 1/4" clearance, then put the motor into a bucket of water and start it up. The torque and vibration should get it to move. If not shift it back and forth from F to R. It's better to take the prop off unless it's a hot summer day......

 

Isn't there another bolt under the steering tab ? maybe not, but a lot of motors do have one back there.

 

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I truly wish there was another overlooked bolt Mr. E. But unfortunately no amount of looking and re-looking has revealed such a gift.

This morning I googled "shaft seized on powerhead" and read through various discussions of this awful topic, quite amazed to read the trouble occasioned by even small engines with this problem.

Westfield's advice is the best I've found. But it's early Sunday morning so I have a good excuse to wait a few hours before starting the engine.

 

They certainly can seize where the driveshaft mates with the crankshaft splines. I know of no easy fix. I recall dismantling an old engine for parts, that would not drop the leg, basically had to destroy the trunk and cut right through the driveshaft, even then the shaft was very difficult to separate from the crank. Not a solution for you though. There may be a lateral thinker with an ingenious solution, but I have never heard of one.

 

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Late afternoon now, I had about a 6-hour long contretemps with this drive shaft seized in the powerhead.



I couldn't make use of Westfield's method, because the engine wouldn't turn, no matter how I adjusted the forward-neutral-reverse, above and below.

When I took the cowling off I was amazed, because this 20-year-old engine looks as if it is brand new. It is practically spotless.

So after a little more useless hammering, I resorted to brute force. I made a tight bridle out of rope around the upper casing, and another one around the lower unit. Hooked a cargo strap to each side of the upper bridle, after having looped said strap around a stout tree outside my garage. The lower bridle I connected via another cargo strap with a big ratchet, to the trailer hitch of my car. Placed padding on the ground so the engine wouldn't get scratched.

I spent an hour then tensioning the ratchet/straps and hammering, and though I tensioned the cargo strap ratchet all I was able, it didn't seem to make much difference with the outboard, but my car inched backwards instead.

Finally of course I got in the car, backed up a few feet, and accelerated it forwards in anger (had done this earlier, but then rather too meekly).

Halleluja! It is Sunday after all; I'd finally gotten this lower unit to come off.

 

Well done ! Hopefully the thing will go back in when the time comes, if there is rust in the splines, may be another drama. It may be advisable to lift the powerhead off and clean the splines if you have an issue there. All you have to do now is work out what broke, better luck there !

 

What broke?



It was the the bottom end of the drive shaft, at least. I pulled the shaft from the housing, and then the tip of it which had snapped off also fell out. The bottom-end splines were also bent and cracked as that photo shows.

After that I held the lower unit upside down and tried turning the propeller while shifting the gear shaft up and down; nothing else fell out, but the propeller only makes 3/4 of a turn before stopping. I guess that probably indicates additional damage.

The top of the driveshaft looked better than I'd expected (bottom half of photo) but I don't suppose it was ever greased in 20 years, or the impeller changed.

This morning I found out that Yamaha no longer has these assembled lower units anywhere, not even in Japan. So I'll have to either get lucky and find something used, or buy the individual lower gearing related parts and have a qualified person assemble them?

The 15hp and 9.9hp Yamahas from 1990 through 1993 have identical parts numbers for the lower units, so that's what I'll be looking for, in the long version.

 

Big job. Best plan would be to get one ( gearbox) from a wrecker, I'd say. You may have damaged gears, which would be very expensive. You will have to take the guts out to see what the damage is. Parts are typically quite expensive, and re-assembly is a bit tricky as you need to make sure everything is shimmed correctly, or it won't be lasting long.

 

It sounds like you are on the hook for a replacement 15 HP motor..... Does it have to be a Yamaha? If not you could try CL, but I am sure you already know that.

 

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It's been fairly good day, on the obsolete outboard gearcase front. lol

Some friends have an eye out and some dealers have been contacted, and should it not lead to anything soon then a good effort has been made.

As to a replacement motor, a friend of mine who is technical consultant for a marine insurance company has perhaps given me a reasonable option.

It will work out. But my goodness what a disjointed mess this used outboard parts sector is, relative to the internet.

Come to think of it, I have a deed-related right to a slip in the neighborhood harbor, which I've never bothered to use. And I could offer that to the classmate's father for a couple of years since it costs more than a motor. It would be nicer than the trailering chore he's got now.

The damn thing is that I'm one of those imbeciles who has trouble throwing old things away.

My father-in-law's 1986 30 HP Evinrude for example; he maintained it faultlessly for years. Then we took it over and the bolts holding the starter motor broke off in the engine, so I lashed the starter motor to the engine with nylon cord six years ago, and it's still OK. I replace a few other things now and then.

But I don't really know whether he is delighted to see his old motor still working, or whether he secretly thinks I should have taken it to the dump long ago and bought something bigger and better!

What counts more perhaps, is that his father and grandfather were fishermen and he is quite expert when it comes to fishing, but I couldn't feed a scrawny cat, if I had to.

lol

 

As Red Green would say: "it's not a temporary repair if it works!".