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I am trying to get lower unit off to replace water pump on a 2005, 90hp 4 stroke, carberator engine. Removed the 5 bolts as recommended, but will not come off, used wood block and hammer and see no sign of loosening. Any suggestions on how to break free? The engine looks almost new. I am trying to learn by doing this myself.

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If you are planning on doing continuous maintenance and repair with the motor go to the expense of buying a service and parts manual. The service manual will show how to do it and determine if banging a 2x4 to free something up or loosening a hidden set screw is the method. I have found that the parts manual is invaluable. First for saving the distributors time when ordering parts but, more importantly, when the time comes that banging the 2x4 to free up a housing, and a dozen springs and ball bearings go flying all over the place, you have a schematic for putting it back together. My rule of thumb is to get the manuals and if I do not feel comfortable studying how its shown, I send it out.

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I do have the manual, but it does not tell how to remove a stuck unit. I looked for a hidden bolt and did not find one. The manual only shows the 5 bolts to be removed. Thanks for response . Only banged hard enough to loosen, but a sledge hammer was looking good. Did not want to buy a new lower unit.

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I have a 2007 Mercury 60 Big Foot 4 stroke and plan to replace the water pump impeller this Spring. There is an excellent video online at Youtube.com. I used the search term: " Mercury Outboard 60HP 4 Stroke Water Pump Replacement". I would also recommend buying the shop manual.
Don't forget to remove the recessed bolt above the trim tab.

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I removed the nut in front of trim tab. I also removed 4 nuts (2 each side) on lower unit. Is there another nut or bolt I missed as the above is all that shows in the manual. How far up does the lower unit housing go into upper unit housing (1/4", 1/2", etc)? I was wondering if this could have corroision impedding removal or perhaps the shaft splines are sticking (hope not). I saw video you refer to, but lower unit did not break free like his did. As I mentioned before, this motor looks in great shape and runs great. Since i did not know when the last time the water pump was replaced, I thought I would replace it and learn. If I can get this project done I might consider rebuiliding fuel pump as the engine sometimes skips, duiring low rpms. Runs great at 3000 and above.
Any thoughts as to removing lower unit?

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Isn't there a shifting linkage that should be disconnected?

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The Mercury Manual does not mention a shift linkage. Either I am miss seeing a bolt connection or the lower unit is sticking to upper housing. I might try to put some heat tape they use to wrap pipe on the upper unit and something cold on the lower to see if this will loosen it up.
Still looking for any suggestions that you might have.

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How long have you owned the motor?
Salt or fresh water use?
How far has the unit dropped after removing all 5 bolts.

Block/trim the engine so it is close to vertical and only 1/2" above the ground or a large block of wood.

If it has only dropped 1/4-3/8" try adding several large flat bladed screw drivers (cover ends in tape), one on each side, one on the front and rear edges.

With a helper, each take 2 handles and slowly twist all together to apply even force along the edge. Work together and don't go too hard. Once you break it free, it will POP!

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I purchased use in Dec 2012. Yes it had been used in salt water but I don't know all its history. The motor and boat were in excellent condition (why purchased) at least visually. The motor only had a rust around the steering control arm connection. The motor inside and out looks barely used except for a few scratchs. There seems to be no rust where unit comes apart and on any exterior painted part.
After removing bolts the lower unit did not drop any even after tapping using a wood block and hammer. I will try to heat upper tonight or tomorrow to see if that helps.

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Perhaps you could clarify a few things.

- Have you placed the the motor in FORARD GEAR as described in the service manual?

- What service manual are you using? Mercury Factory? Seloc? Clymers? Other?

- You said you removed five bolts but then later say you removed nuts. Which is it?

- What is the serial number of this 2005 motor?

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Before going thru all that heating and banging and prying I would suggest talking to a knowledgible mechanic firmilar with Merc's and ask him if you missed anything. Shops will usually answer questions. I would hate to see anyone do damage when a couple of good questios cpould be asked.

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Building on aeriksen's post. I find most shop mechanics are extremely helpful with information but, at some point, when does it serve us better as "do it yourselfers" to send out some projects. They may very well say bring it in. The initial freeing of an old motor is a tough one. A motor with an unknown history may very well have other issues involved once separated where a trained eye might see other maintenance or repairs to address while accessible. I would call around and research the local boat shops/mechanics and if the water pump replacement still seems too big of a mountain for you to do (I hate it when I hear stories of how easy it is to do something from others when each experience is unique) go with the one that you are most comfortable with. It would break my heart to read how a casting broke while you were playing with it. You could do the pump replacement next time with the knowledge that the interior of the motor was dialed in.
gchuba

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I am using the mercury manual for engine. I did try to remove in forward gear. S/n 1b102580. 90 elpt sw, 90 hp. I will call around to a mechanic for advice. thanks for the advice and you are right, I do not want to break casting or do any damage. It is never as easy as they show on video, ha. I will look at again tomorrow after spraying penetrating oil on bolts and seam. By the way, I removed 5 nut and washers. The studs are still on engine.

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Here's my .02. Don't hammer against even with a block of wood any part of an aluminum housing because it is usually thin and will crack or break. The strongest part of the two housings are where they bolt together. You are probably going to have to persuade them apart with a hammer and screwdriver at the seam between the two housings. There may even be a relief cast into the housing for just that purpose. You're gonna have to get mean with it and by the time the job is done both you and your outboard are going to have some new scars but hey, it's nothing a little touch up paint can't fix.

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What? They should be removed.

Since this unit has not been "dropped" in who knows how long, I say take it to a mechanic. Once it has been removed, it will drop easy next year with no fuss. You can take over the annual servicing.

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No, the studs stay on the exhaust housing and the lower unit drops down off of them.

Yes, there are just the five 10 mm nuts to be removed.

It can be EXTREMELY difficult to remove an aluminum casting from over a stainless steel stud if it has not been done in a while. This summer I struggled to remove a lower unit from a small motor that had only one stud. I couldn't do it and ended up cutting the stud and drilling it out after the lower unit from finally dropped.

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I confused stud with bolt. Thanks for the correction.

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Thanks for the comments. I think I will call around next week and see about talking to a mechanic and perhaps take it in for service. It does not want to budge and I do not want to break anything by pounding on it. I hope they can get it off, plus I might get a few other items taken care of.
Again thanks for all your comments.

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I echo Tom Clark's observation. This time go to a professional and at this time of year let him earn your $$. Then do this (if only to drop the lower unit to grease) every year.

The lower unit of my 199140hp Yamaha had not been serviced till 2003. Add insult to injury the bolt under the trim tab broke off....no biggie until you realize that it has perhaps a 3 inch shaft that is also set solid on the lower unit side in addition to the studs which were shiny new.

Figuring that the professional would use essentially the same tools as me....perhaps with a little less squeamishness with regard to the paint, I worked on it for 2 to 3 months going thru an assortment of pry bars and several packs of toilet bowl shims untill I had enough clearance to cut the bolt. That then led to another adventure of locating an awesome tool called a Titan Stud Puller to extract the bolt on one side and a drill to drill out the 3 inch shaft on the other.

All in all it would have been well worthwhile to go to the pro and then do this annually to prevent bolts/studs from seizing up.

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To docsoma. Thanks for the tip about Titan Stud Puller. I always battled a broken stud that had a little bit of bite left with vice grips. Also, to Tom Clark referring to "drilling out the stud..." . I am I complete agreement. The biggest mistake I made years ago was listening to a salesman at a parts counter who stated "...all you have to do is drill the center of the bolt and use an 'easy out' extraction tool...". Right! Now I had a flush broken bolt with a flush broken easy out (case hardened steel) in the center of bolt that was now undrillable. If I recall I rate that job as 4 bloody knuckles. Now I drill, collapse the bolt, clean with a dental instrument, re-tap.
gchuba

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Talked with Mercury Outboard and they suggested having someone jiggle the drive shaft by jiggling the top manual crank flywheel (don't know correct name for this). Sometimes shaft gets stuck and this might help. If not, recommended taking to a dealer. I will try later this week (shop not heated and its really cold outside/inside) and will let you know outcome.

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Drop the skeg(remove) I think there is one more nut (bolt)under there, ( I think) maybe mike

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Well I tried jiggling the cranking head of motor, but the lower unit would not drop. I removed the 4 fasteners (2) ea side, and the locknut and washer as indicated in mercury manual. I looked all over for a hidden bolt and did not find one. I will try to find a certified mechanic to see if they can get it off. My only thought there might be some corrosion around the studs and the housing.

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Did you take off the trim tab that sits behind the prop? There may be a hidden bolt under it or in front of it just above the prop.

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Well I got lower unit off. The rear stud and 1 of the front studs had corrosion between stud and housing channel. After removing the corrosion, it looked like wet salt.
To remove the lower unit I used (2) 3/4"x6"x 2 1/2 wood with (2) 6"x2"x 1/4" steel plates inserted between the two wing flanges where the units would separate. I drove a wedge in between the steel plates putting pressure on the two wing flanges. This formed a gap in which I was able to insert large screw drivers. I had to keep working it to get it down and with some help they came apart.
I did break a thin piece above the anode, which I did not realize was thin. I am having it welded tomorrow (tig) for around $50.
The pump was fine, but I replaced. There was some corrosion buildup in between water pump base at bolt heads which I cleaned up and then replaced all gaskets that were in kit. I will eventually replace water pump base flange as it showed signs of pitting. Btw, the lower and upper unit did not have any overlap, but we're flush seated together.
I am glad I got to see condition of unit . overall it was in great shape for being a used motor/boat. Hoping this will last a long time.
I probably should have taken it the first time to let a professional mechanic do the work, but I had to try.

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I wanting to assume the boat mechanic would have had to do the same thing you did to get the lower unit off. Don't feel bad about a few scars on your rig, it's nothing a little JB weld and OEM color matched paint won't fix.

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We have all done a project like this a first time. Congrats for your accomplishment. Clean the heck out of everything before re-assembly. Just think, a small busted tab and no busted bones.
gchuba

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We have all done a project like this a first time. Congrats for your accomplishment. Clean the heck out of everything before re-assembly. Just think, a small busted tab and no busted bones.
gchuba