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DIY lower unit rebuild?


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#1 Animal

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Posted July 03 2011 - 10:56 AM

Last spring I paid a mechanic about $5 bills to rebuild one of our lower units.Eight trips later,we noticed an oil slick while fishing,checked the bilge,all good.Yesterday,though I noticed a leaking lower unit,in the driveway.Same one.My mechanic says theres gotta be a vibration,or "out of balance"problem,as this isn't a "maintenance"issue,and these gaskets should last basically forever.
SEI,outta Florida sells an aftermarket lower unit for $845,but right now isn't the time for me to spend like that.
I think I'm going to rebuild it myself,and I'm waaaaay open for any advice or suggestions.Thanks.
It's a 1998 Mercury 200 Offshore EFI.:shock:


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#2 fishfood

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Posted July 03 2011 - 11:48 AM

Gearcases require special tools to turn retaining nuts, pull bearing carriers, properly shim, etc. It would be very, very difficult to do without those tools.

Whoever rebuilt your lower unit should be on the hook for this. He either didn't put it together right, didn't install the seals properly, or didn't bother to make sure the parts were in spec. You don't rebuild a gearcase without taking 15 minutes to make sure the prop shaft is straight, for example.

Where exactly is it leaking?


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#3 Bill A

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Posted July 03 2011 - 11:50 AM

I bet the parts to assure you eliminate the bent shaft or other source of vibration costs as much as a used replacement foot. Some years back I made a similar decision and got a used unit from a well known NJ outboard graveyard. No problems at all. All I did was change the fluid, water pump and put it in.


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#4 Animal

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Posted July 03 2011 - 11:52 AM

It's leaking from where the prop meets the unit,not from the exhaust.


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#5 Animal

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Posted July 03 2011 - 1:16 PM

From here you can see the oil running down the skeg,and the milky oil in the unit.:(

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This is going to suck,I think.


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#6 keeler

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Posted July 03 2011 - 5:20 PM

Changing the seals is a medium skill job and requires some special tools and knowledge.
Rebuilding a LU on the other hand is a very skilled job and requires not only the tools, knowledge and expertise but also an assortment of spacers and shims. I , who will try a lot of things, wouldn't even consider rebuilding a LU.


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#7 Animal

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Posted July 04 2011 - 11:57 AM

I bet the parts to assure you eliminate the bent shaft or other source of vibration costs as much as a used replacement foot. Some years back I made a similar decision and got a used unit from a well known NJ outboard graveyard. No problems at all. All I did was change the fluid, water pump and put it in.


Hey Bill,this NJ boneyard got a name?Thanks.:D


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#8 foulhook

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Posted July 04 2011 - 9:14 PM

Last spring I paid a mechanic about $5 bills to rebuild one of our lower units.Eight trips later,we noticed an oil slick while fishing,checked the bilge,all good.Yesterday,though I noticed a leaking lower unit,in the driveway.Same one.My mechanic says theres gotta be a vibration,or "out of balance"problem,as this isn't a "maintenance"issue,and these gaskets should last basically forever.
SEI,outta Florida sells an aftermarket lower unit for $845,but right now isn't the time for me to spend like that.
I think I'm going to rebuild it myself,and I'm waaaaay open for any advice or suggestions.Thanks.
It's a 1998 Mercury 200 Offshore EFI.:shock:


I know that nobody likes to dump money but we are talking boats here:)

SEI makes some nice LU's. For $845 I would go that route and be done with it and go fish. Season is short up here.


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#9 bospa357

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Posted July 04 2011 - 11:38 PM

I was in a similar "boat" last year. After pricing all the parts and labor, it was going to cost me almost as much as the complete LU through SEI. I went with the new unit from SEI and you also get a
warranty with it.


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#10 Michael P

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Posted July 05 2011 - 4:38 AM

I had to bite the bullet myself this spring. I spent closer to 2K with labor and a new water pump. I also opted for a Merc backed rebuild. It's the only motor on the boat. I want it to get me home.


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#11 Billybob

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Posted July 05 2011 - 6:14 AM

What did the local mechanic actually do in this rebuild?
Seem to me that he screwed up and should stand behind his work.
That being said, it could drag on and you lose the rest of the season.
Might be worth it to you to get a new unit.


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#12 keeler

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Posted July 05 2011 - 10:54 AM

One other thing to consider is the warranty and what are the exclusions etc. SEI gives a 3 year warranty ant that covers just about any event including running into a rock and busting the unit open. I haven't seem factory or certified rebuilds with a similar period and not many if any of those that cover collision damage.


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#13 bospa357

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Posted July 05 2011 - 11:20 AM

When I checked into it, SEI's warranty was far better than factory parts.


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#14 makorider

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Posted July 05 2011 - 11:42 AM

I'd guess he's talking about Trixies. Its in Lanoka Harbor, Waretown, or Forked River....cant remember.


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#15 Stix an Strings

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Posted July 06 2011 - 3:21 AM


I had similar leak at the prop shaft on my boat.I pulled the lower unit myself but then took it to my marine tech, He found ten feet of mono that got wrapped in the shaft and destroyed the seal.



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