2002 75 HP merc bearing problems

Davcar

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Aug 22, 2003
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14
My cousin has a 2002 75 hp merc 2 stroke with auto oil injection. The motor developed some strange noises one day recently. To me it sounded like a bearing had gone. He took it to a marina and the guy listened to it and said, yes its a bad bearing. In further conversations with a couple other marine mechanics they are saying its not uncommon. That regardless of manufacturer the auto oil injection systems are or can be a problem. My guess is that the motor wasn't getting the proper oil delivery it should and the bearing went. So now what. To take it to an official Mercury mechanic/marina they are talking $4000+ for a new powerhead and labor. First, I think we have to find out what caused the problem so as not to repeat. Then, there are numerous places online where you can buy a rebuilt powerhead for $2000 or less with a warranty. Doing the work ourselves doesn't scare me at all and my plan would be to do some disassembly of the powerhead to see what damage occured, partially because I'm nosy and in part to make sure it really is a bearing issue. I think after re-assembly of new parts I'd then eliminate the oil injection and run pre-mix...like in the good old days. Seems to me like there are a lot of older outboards still running today that were pre-mix fed. Does this problem ring a bell with anyone? Anyone have any experience with any of the rebuild vendors out there?
 

jbjennings

Captain
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Jul 18, 2007
Messages
3,903
Re: 2002 75 HP merc bearing problems

There's no reason you can't rebuild it yourself. If the oil lines have no cracks and the gear hasn't stripped on the pump, the oil injection systems are otherwise reliable. I would look to a lean carb situation, oil line cracks, stripped pump gear, vacuum leaks for the source of the problem. There's no reason you can't rebuild it yourself. If the crank has pressed on rods and bearings, you can send it out and have it done. If you need, I'll find who it was that did my yamaha crank with pressed rods/bearings and pm you. The blocks can be bored if necessary by any marine rebuilder. I'm not a professional, so can't comment on the frequency of such a problem, but like any machine, sometimes they break. My dad's 2007 yamaha 25hp had a main bearing cage disintegrate and tore up the pistons and cylinders. It had a vacuum leak due to a damaged idle adjustment screw.
You can google the procedures for blocking off the oil pump; many times there are several unexpected steps to doing this, so make sure you know the right procedure or you'll hatch a rebuilt block.
good luck,'
JBJ
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 2002 75 HP merc bearing problems

Doing the work ourselves doesn't scare me at all and my plan would be to do some disassembly of the powerhead to see what damage occured, partially because I'm nosy and in part to make sure it really is a bearing issue.
This is the best course and this series of motors are known for piston skirt breakage and center main failures. Most of the time this is caused by over propping or lugging motor. Also it does not have pressed together crank and rods are removable. If you need/have questions on machine work you can pm me .....Hey JB call me sometime:D
 

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: 2002 75 HP merc bearing problems

This is the best course and this series of motors are known for piston skirt breakage and center main failures. Most of the time this is caused by over propping or lugging motor. Also it does not have pressed together crank and rods are removable. If you need/have questions on machine work you can pm me .....Hey JB call me sometime:D

I may have to........ I think I got another clutch dog and gears for a 25 merc...... Be careful what you ask for!!!! :)
 

Archer59

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Joined
Sep 25, 2009
Messages
28
Re: 2002 75 HP merc bearing problems

I have a 94 merc 75 hp that the oil pump failed. Lost a cylinder. After repairs did not re-install oil pump. Been mixing gas for a long time now. No lubrication issues. :)

Nick
 
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Davcar

Cadet
Joined
Aug 22, 2003
Messages
14
Re: 2002 75 HP merc bearing problems

Thanks for the input guys. I may be back here to update or ask questions as we get into it.
 
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