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Thread: Gearcase Failure 101......
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12-01-2010, 08:46 PM #16
That is an interesting pinion i'd like to see pictures of the fwd gear,who shimmed it prior.another option is to have a larger key and slot machined into case and carrier works great
21 SuperBoat VF200 Yamaha SHO
Bender Clan memberEroshibend Yamamoto
2015 King of the Cut
2016 King of the Cut
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12-01-2010, 09:40 PM #17
The keyway was a bit abused prior to assembly and pinning the last time so instead of using a stock key, one was machined with a slight interference fit so it was snug when put together. I don't have all the parts in front of me right now but I'll get some shots of the FWD gear for you Bender. After stewing about this all day and reading some of these comments the best I can come up with is this.....
I spun the carrier 3 times this summer.....two of which didn't make itself known until I tried to use reverse and had none (no gear mesh whatsoever) soooo....I spose some damage to the pinion could have been done then and was somehow overlooked when it was reassembled last. That is the easiest explanation I can come up with.
Apparently I missed the part in the manual where it stated that the final torque on the carrier nut needs to be done AFTER it is bolted up to the midsection.1976 Hydrostream Viper - 2.5 EFI
Resto Thread Here
2010 Go-Pro Stuff
"The true soldier fights not because he hates what is in front of him, but because he loves what is behind him." -G. K. Chesterton
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12-01-2010, 09:59 PM #18
Jeff don't feel bad b/c I was just about to post what Lynn had to say. Once that carrier backs off the preload between the ring & pinion is gone, end play grows, bearings move, etc etc etc.... Gears are tough sombitches and that makes them tough sumbitches to inspect when you reuse them. I'd bet that if they were inspected very close (with a loupe) you would have found cracks in the root or the tip and probably in between both.
Sucks man....you worked sooo hard to get er done and kept having issues. Glad when it did puke you guys didn't get hurt or anything!
Wanna go to Ohio Sunday?Last edited by njj502; 12-01-2010 at 10:07 PM.
Sunsation 32 Dominator - 496 MAG HOs
Nothing runs like a Deere when a CAT's on it's ASS!
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12-01-2010, 10:42 PM #19
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12-01-2010, 10:50 PM #20
No mike his is much better
21 SuperBoat VF200 Yamaha SHO
Bender Clan memberEroshibend Yamamoto
2015 King of the Cut
2016 King of the Cut
2017 King of the Cut💪
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12-01-2010, 10:51 PM #21
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12-02-2010, 12:18 AM #22
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12-02-2010, 01:00 PM #23
Jeff, I want to see all the parts if you still have them. I'll bring my AFA (Applied Failure Analysis) books with me.
Sunsation 32 Dominator - 496 MAG HOs
Nothing runs like a Deere when a CAT's on it's ASS!
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12-02-2010, 04:46 PM #24
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12-02-2010, 06:35 PM #25
Yeah I'm glad we made it back that day of the (I think) second time it spun. I was not, however, glad that it puked again. You will get it bro, I'm sure of it!
Sunsation 32 Dominator - 496 MAG HOs
Nothing runs like a Deere when a CAT's on it's ASS!
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12-02-2010, 07:06 PM #26Screaming And Flying!
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Blower units
My buddy has blown more lowers than power heads....I built the powers and lowers are cheep and replacable. Put a nose on one and go... Fissin lowers are around all over... weld the nut,,,,
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04-11-2011, 01:11 AM #27Junior Member
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<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> I have the same problem spinning the carrier on my Mirage. It spends more time broke than it does fixed. Sorry to be so long winded, but that’s the way I am. I keep thinking of something else I think others should hear (but I’m not conceited…just ask me).
I have come to the conclusion that the 200 lower units I have been using are not made for surface piercing applications like mine. Who knew? I mean, just because Mercury “says” that they are not made for surface piercing applications, doesn’t mean I can’t do it, right?
But seriously, I think that the problem is that the 200 rear propshaft bearing is not big (or strong) enough to be “side loaded”, and when only half of the prop is in the water (like mine), it is most definitely being side loaded. At least some of the thrust is being applied up towards the powerhead (instead of straight forward to the forward bearing.) by the propeller only having bite on the bottom half, and also by the prop slapping the water.
This thrust may actually be to the side, but it doesn’t matter which direction it is, just as long as you realize that this thrust is perpendicular to the forward direction (or side loaded). And that this side load is fairly constant in one direction for a constant height of the propshaft to water surface. As this height changes, so does the direction of side load, but as long as some of the prop is out of the water, there IS side load on the rear bearing. Once the entire prop is submerged, the side load goes away and the propshaft just wobbles around within the clearances it has and all the thrust is again directed forward.
I don’t think the 200 rear bearing is strong enough to put up with this side load for long, or maybe it just isn’t getting enough oil. Either way I believe that this bearing wears prematurely, and once it wears sufficiently to give the shaft enough play to press the seals out of round, TROUBLE ensues. The oil leaks out, the water leaks in, and then the conditions are right for a little doomsday party inside the lower unit.
Higher pitch props (I run a 28p and 30p) will have higher upward thrust (and there fore fail sooner) because the blades are more horizontal or flatter if looked at from the side of the boat. Also larger diameter props will exert more side load because they have a longer “lever” (more distance from center to tip of blade). Bigger bladed props exert more force because they have more surface area slapping the water. So I’m thinking that a small diameter, skinny blade, smaller pitch prop would give the least problems (can anyone say cleaver?).
Some people believe that seals fail, let the grease or oil out, then the un-lubricated bearings fail. Me, personally, I don’t believe in premature seal failure, I believe that the bearing wears first, then the seal fails, then it snowballs because the lube does leak out and hastens the bearing failure (and I’m not just talking lower units, I mean ALL bearings with seals, like the wheel bearings on the trailer).
I think that all propshaft seal failure, all spun carriers, and 99% of catastrophic lower unit failures, are the result from this strength flaw in the propshaft rear bearing, they are just discovered at different times in the cycle of failure.
I believe that the spun carriers are a result of the rear propshaft bearing either seizing up, or wearing enough that the propshaft contacts the carrier and spins it (as you have seen, pins or screws will not stop this).
One thing to try for less stress on this small rear bearing, is to put the biggest gear (lowest ratio) you can get in the lower unit and then run a smaller pitch prop. I have been running a 28p to 8400 rpms, but on the old 2.0:1 gear sets (they’re cheaper, what can I say). If I changed gear sets to a 1.62:1, the math works out to a 22.68 pitch to get back to the same rpms, so I would probably try a 23p to start. Just know that this smaller pitch prop will be turning much faster at the same speed, and if the rear bearing fails, it will probably go catastrophic faster.
The best solutions that I can think of are to install the heavy duty rear bearing carrier (that has 2 bearings instead of 1 to better handle the sideload) or install a sportmaster lower unit (which is designed for surface piercing applications).
I , myself, am in the market for a sportmaster lower unit, or a motor with a sportmaster, but being a cheapskate, I probably will not buy one unless its cheap and in good shape (hard to find, I know). If you have one for sale DO NOT REPLY TO THIS THREAD, that’s just rude. Put it in the marketplace section and I will see it.
All this is just my opinion, I give it for free, and remember you get what you pay for.
Bear'91 Mirage Jaguar
'04 Yamaha 240SX
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04-24-2011, 11:32 AM #28
I had the same thing happen to my stock 200 case and I was not surfacing it. I had the top four holes plugged and Merc inlet plates over the holes for better water flow. I was just a hair under 2" below pad.
The prior owner had bent the propshaft so I replaced it and the mechanic said all "looked" healthy inside so I ran it for the season. I had it on a 200 EFI on a heavy bassboat and could run it in the mid 70's.
I , too, felt something running one day as you described before it let loose but I got off the lake immediately. I thought it was the engine that made that sound and what I felt. But, I have a habit of spinning the prop when tying down and it did not sound right.
I took the lower to the mechanic the next day and he said it was all tore up inside. Gear parts everywhere and it all ruined. Thankfully the case survived. He was confident that one of the gears was cracked from the blow the bent porpshaft suffered and was not visible to the naked eye!!!!2013 Allison XB 21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
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