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TOPIC: HELP Mark78 L/U
HELP Mark78 L/U 15 years 1 week ago #30190
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I'm live in my garage and just pulled L/U. The way the impeller looked I don't see how it can go both directions?? Also gear oil looks like caramel color I would say. Any input will be greatly appreciated. Joe
Just found this little jem on shaft seal under impeller. I know this can't be good!!!! 
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Re:HELP Mark78 L/U 15 years 1 week ago #30195
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dont loose that, its the key for the water pump impeller
does the lower unit turn well |
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Re:HELP Mark78 L/U 15 years 1 week ago #30196
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Yes, in both directions.
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Re:HELP Mark78 L/U 15 years 1 week ago #30197
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OK I see where that key came from.
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Re:HELP Mark78 L/U 15 years 1 week ago #30200
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can we see a closeup of the water pump area
while the gearfoot is off, blow compressed air in the pee hole, water tube running up the tower, check for obstructions look for the plug on the top of the block Conrad mentioned blow air backwards thru the block from that plub hole, again your checking for obstructions, old rubber impeller blade pieces possibly |
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Re:HELP Mark78 L/U 15 years 1 week ago #30201
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OK does that impeller key supposed to have a tab that fits into that slot in shaft cover? If so it's broken off.
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Re:HELP Mark78 L/U 15 years 1 week ago #30202
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the key is fine the flat side lays on the flat of the shaft, you clock your water pump impeller so the groove in the impeller lines up with the key and press it on
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Re:HELP Mark78 L/U 15 years 1 week ago #30204
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Close ups
The key doesn't have to go in the slot in the 3rd pic? |
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Re:HELP Mark78 L/U 15 years 1 week ago #30207
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After enlarging this photo the area that I circled looks chewed up. Do you see a slot in that area where the key would locate the impeller? Looks like there is water in the LU judging by the color of the oil but maybe you knew that already.
Melanie 
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Re:HELP Mark78 L/U 15 years 1 week ago #30210
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The impeller doesn't look chewed up and yes the l/u oil looks like caramel. Joe
Oops wrong pics.. 
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Re:HELP Mark78 L/U 15 years 1 week ago #30211
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I wasn't referring to the rubber portion but the inner metal area that is in contact with the drive shaft. There should be a slot in that area that the nub on that key fits into.
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Re:HELP Mark78 L/U 15 years 1 week ago #30212
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That shows good in second pic. The inner sleeve isn't chewed up.
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Re:HELP Mark78 L/U 15 years 1 week ago #30214
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Yes, looks good.
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Re:HELP Mark78 L/U 15 years 1 week ago #30215
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The key is held on the flat spot on the shaft with some grease or something similar!
You then carefully twist the impeller in to line up the slot and press it into the housing. Verify engagement of the key. Install a NEW impeller. |
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Re:HELP Mark78 L/U 15 years 1 week ago #30216
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Thx, I've seen someone say you can get these at Napa, is that true? Is the impeller supposed to spin both ways? The oil looks like caramel, what's the best to use? Thanks, Joe
Is the key supposed to fit in this slot?? 
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Re:HELP Mark78 L/U 15 years 1 week ago #30220
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The impeller spins both ways !
The key does not fit where you think it does ! The key lays on the flat spot of the SHAFT and drives the impeller. Where you are pointing with the arrow is not where the key goes. |
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Re:HELP Mark78 L/U 15 years 1 week ago #30221
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Joe, if you found the key in the shaft seal, it came out like I said. You've got water in your oil. My bet is the upper bearing and seal are done. The driveshaft probably dropped down and the key came out. The key goes in the "flat" spot on the shaft and the key dimple goes in the groove on the brass inner bushing of the impeller. A complete tear down is in order here!!! Don't mess around, and do it right. You did say you had clunking, clanging in the lower unit.......that tells be somethin' is goin' on in there, and it's not good.......
Jim S. |
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Re:HELP Mark78 L/U 15 years 1 week ago #30223
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OK The key might have fell out when i took impeller out and I didn't know it was there. I can rotate drive shaft in both directions without any grinding or other noises. I understand how that key goes in but i still can't see how it spins both ways from how it looked in the pump housing. I'm not arguing or trying to be a pain in the ass, i just understand it better if i visualize it. Do i have to have special tools or can i improvise? where can i get a rebuild kit from? Thx, Joe
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Re:HELP Mark78 L/U 15 years 1 week ago #30224
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It might be me but the driveshaft looks like it is worn down in the area of the impeller and if so the key might slip in the impeller.could be wrong.
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Re:HELP Mark78 L/U 15 years 1 week ago #30225
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Your ok Joe! I can understand your frustration. Yes, the impeller does turn both ways. Reverse is low rpm, so the impeller vanes will stay ( from looking down ) pointing to the left...although I have seen a worn impeller flip one of the vanes in the opposite direction. EastCoast Marine may have what you need ( gaskets seals etc. ), but you may have to hunt down the impeller, it is NLA. Napa may have a Sierra brand impeller. Just search the internet, you may come up with something. The last one I bought was from Vintage Outboards and was not cheap. Sometimes they pop up on Ebay. Do a Google search for the number found on the bearings, I've found several on Ebay as well, actually bought some in bulk. Get yourself a manual too!! Good luck with your search and let me know if you have any questions.
Jim S. |
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Re:HELP Mark78 L/U 15 years 1 week ago #30226
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IT just flexes the blades in the other direction when it spins backwards, the Rubber is jsut stiff and stuck in the direction it last spun in when it was put away for winter most likey, A new one will have straight blades. and be more flexible.
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Re:HELP Mark78 L/U 15 years 1 week ago #30227
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Thx all, I'll do some research and see what I come up with..
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Re:HELP Mark78 L/U 15 years 1 week ago #30229
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Positive displacement pump, there's no room for the blades to "flip". A good housing and impeller will not allow it. If that were the case, you wouldn't get half a season out of one. I've run one in reverse out of curiosity then disassembled it, vanes were in the same direction. I have an intimate relationship with these motors and am well aware of their intricasies........
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Re:HELP Mark78 L/U 15 years 1 week ago #30230
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You really confused me now!!lol you said before impeller spins both ways and this one says it doesn't..
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Re:HELP Mark78 L/U 15 years 1 week ago #30231
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Never mind, read it wrong..
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Re:HELP Mark78 L/U 15 years 1 week ago #30233
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Time to invest in a manual.
Find out how these thing work. Best to go over the WHOLE motor. It runs , but I think it needs lots of work. Inspect pistons and rings ( thru bypass covers ) and tear the lower unit apart. Inspect / evaluate everything before spending any money on parts. |
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