Another stuck lower casing cap 1999 F50

[ChuckB1954]

I have my slide hammer hooked up to the prop shaft, but despite many tries, the lower casing will not come loose. I have tried applying heat to the outside of the lower casing in the two areas with no luck. I am thinking of trying tomorrow to apply heat to the inside of the cap. I plan on replacing the cap anyway. Bad idea? Any other suggestions?


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[99yam40]

I would think that the square tubing would give some when using that.
also how are you holding the lower unit from moving, that also needs to be held where it does not move/give when using the slide hammer.

and I hope you removed the shift shaft before trying to pop that out

[ChuckB1954]

I would think that the square tubing would give some when using that.
also how are you holding the lower unit from moving, that also needs to be held where it does not move/give when using the slide hammer.

and I hope you removed the shift shaft before trying to pop that out

The square tube reinforced with the washers is solid. The blows with the slide hammer are hitting home. The picture of the square tube is after a hundred blows.
If it was flexing, the tube would be bent out of shape. That is not the case.

The shift shaft does not have to be removed for the prop shaft/housing to slide out.
The only thing that is attached to the shift shaft is a cam that makes contact with a spring loaded plunger in the end of the prop shaft.

I tried extreme heat when I got home. Still no luck. That cap is stuck solid.

[ChuckB1954]

Time to break out the cutting wheel and drill. I plan on removing the outer ring portion of the cap, should be easy. Then, only being held by the inner ring, it should come out with the slide hammer. Like I said before, I planned on replacing the casing cap anyway.

[ChuckB1954]

With a little cutting and drilling, I was finally able to get the cap to slide out after removing the outer ring.

The lower casing looks pretty good and should clean up fine.

All the gears look fine. The bearings look to be in decent shape too, although I might replace some of them.


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[ChuckB1954]

Now the bad news..

Both the prop shaft and the drive shafts have grooves worn into them by the seals.

The prop shaft, along with the light grooves, has some scratches from when the seals were replace without removing the cap. The large pitted area shown is out of the way of the seal contact area. The drive shaft has some major grooves.

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I can still buy the prop shaft, although a little pricey, but the drive shaft is no longer available and even if it was, it is very expensive.

What do you think I should do? Just buy the prop shaft and put it back together, or put it together as is and cross my fingers and hope
water doesn't get into the lower unit??

[99yam40]

you could have a machine shop weld and resurface.
or just polish and cross your fingers

[robert graham]

Maybe you should explore finding a good used lower unit that you could bolt right on?....

[ChuckB1954]

you could have a machine shop weld and resurface.
or just polish and cross your fingers

I was thinking about that. I could even do that myself. The only thing I worry about is if I MIG it, the material would rust.
I suppose a machine shop would use something that would not rust.

Maybe you should explore finding a good used lower unit that you could bolt right on?....

Most the used lower units I have saw are very expensive and it would be risky not knowing the internal condition,
which could be as bad or worse than the one I have.



I am kicking myself.. a few months ago, I had a chance to buy this used 2000 F50TLRX, a year newer than mine, for $500.00. It had good compression, but was missing the ignition,and the cover.

50.JPG

I am going ahead and buying a new prop shaft. One from China is 100.00, OEM Yamaha Is about 200.00. I will go with the OEM one. New cap also OEM instead of Chinese.

I took the part numbers off the bearings and found some Japanese ones for better than half the price.

Still contemplating what to do about the heavily grooved drive shaft.

[99yam40]

spin it and remove any sharp edges and polish to real smooth.
new seal may hold up for years

not sure if you could get a speedy sleeve on there

[ChuckB1954]

spin it and remove any sharp edges and polish to real smooth.
new seal may hold up for years

Thanks, exactly what I will do.

The good news for the drive shaft is that the area where the two main seals, #32 ride, is smooth. Look at the second picture above. To the right in the picture, you will see the faint marks where these two large oil seals ride. This is all that separates gear oil from water. This area is in excellent shape. There are no other drive shaft seals, as verified in the parts diagram below.

The first worn groove is near #34, which is described as "oil seal cover" and is more like a rubber boot. Pre assembling my parts, the lip for this cover is just below the first groove. It is not what cause the groove.

Actually, the more I look at it, I realize that both grooves are on each side of the rubber impeller, equally spaced on each side of the woodruff key slot. Look at picture # 2 above.

Just wondering what could have caused these two grooves..

My theory, the grooves were caused by too much bearing play at one time, allowing the shaft to rub on #26 and # 22, which is thin, sharp, metal. These two parts line up with the grooves.

I don't think I should worry about it.

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[99yam40]

if that is true then I would make sure the bearings are all in good shape.
that much movement cannot be good.

maybe there was a lot of sand/ mud/ shell run thru the pump at times that caused those grooves
just thinking while typing

[ChuckB1954]

if that is true then I would make sure the bearings are all in good shape.
that much movement cannot be good.

maybe there was a lot of sand/ mud/ shell run thru the pump at times that caused those grooves
just thinking while typing

The current bearings seem as they should. I'm thinking it could have been caused by the shaft flexing due to an oversized prop. I had to lower the pitch 2 or 3 values to get the RPM's correct at WOT. The engine was really lugging when I first got it and would not go past 2500 RPM's @ WOT. Between that and heavily handing the throttle might have cause those grooves.

[99yam40]

I would not think a 50HP motor could flex that shaft

[ChuckB1954]

I would not think a 50HP motor could flex that shaft

Your opinion may vary, but I think it is very possible. I can push down on the shaft sitting between two blocks and it will flex, shown with a dial indicator. The bearings are tight. Those marks were definitely made by the outer plate cartridge (#26) and the insert cartridge (#22) making contact with the shaft and I know those two parts did not move. It is logical that when you are running you engine wide open and it is only reaching less than 50% of the recommended RPM's (2500 instead of 5500 RPM's) you are putting a lot of stress on your engine and drive train, especially if you shove the throttle wide open from a dead stop.


If you look closely can see the two marks in question on each side of the impeller.
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