stuck lower unit

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salvageman

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Apr 18, 2011
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Hi, I have a 2006 Mercury 90 EFI 4 stroke OB. I was going to check the impeller because I had no water flow but the outdrive seems to be stuck on even though I have removed all 5 nuts (two on each side, one underneath). In the videos I watched there was no mention of any reason why it wouldn't pop off with some persuasion. Online, I read that the shift rod and shift shaft may be stuck or (less likely) the drive shaft could be stuck in the powerhead. I can get a small space to open towards the rear of the engine but the front is still tight. Should I be thinking to remove the shift rod spring clip (if I can find it) as mentioned in another forum?
 
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Maxz695

Guest
Re: stuck lower unit

if you have a zinc fin you need to remove it there is a plastic cap covering the bolt to hold it on after removing this there will be a nut holding th back potrion of the unit it should then come off relatively easy. also just in case info added here some water does leave the engine through the exahust and the prop but you should be getting a steady flow through the tall tale. disconnect the hose from where the tall tail is going and see if you have flow there when running if not move on to thermostat etc working your way back until you find the clog. if you have the unit off you can hook a garden hose to the copper water pipe and see if water flows with the Tstat removed this would be good. then you know you clog is between there and the tall tale which is smaller in diamiter than anywhere eles in the system remve the tall tale and run a hanger carefully through this to clear it out. if the impeller hasn,t been changed recently it would be a good idea to replace it scuffing and scoring form sand dirt etc can harm the surface of the impeller cup causing loss of pressure. the impeller may look god but may have lost it,s ridgitity also reducing pressure needed for a good flow hope this helps
 
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salvageman

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Re: stuck lower unit

Thanks for the reply. I don't think this engine has a bolt under the fin but I will double check. I am thinking that the shift rod and shift shaft are stuck together. I read somewhere that they can be removed together by removing a spring clip up high under the front of the cowling. I have since been told that I will void my warranty if I remove the lower unit at all...difficult news for a hands-on guy like me. I may have no choice at this point but to take it to a dealer and spend a lot of money for a simple impeller check/replacement. I have also been told that I may have a clogged tube and that compressed air might solve my problem but now I feel I have to get the stuck parts apart.
 
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salvageman

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Apr 18, 2011
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Re: stuck lower unit

The question remains: how do I free the lower unit...in your reply assume it has something to do with the shift shaft, the front of the lower unit is the part that is still tight together, I can get space toward the rear.
 
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Maxz695

Guest
Re: stuck lower unit

I am firmiliar with I/O having a screw clamp to remove the lower unit but i havn,t seen one on an outboard yet, although it is possible, but if there was I would think the lower unit would have an access point for it, or it will have to come down somewhat to get to it. Sorry I can,t be of more help but if the back has seperated try puting it back up, and then get the front to come down it may be binding thats all I can think of this would just be guessing I hope someone here would know and help soon. I do beleive your right if you remove the shifter link in the front of the power head lower cowling area it shoul come out in one piece at that point not sure how to undo it though
 
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Maxz695

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Re: stuck lower unit

this is the other part I has to remove to get to the last NUT under it
 
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salvageman

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Apr 18, 2011
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Re: stuck lower unit

I just spoke to a dealer who told me that unless I disconnect the shift shaft it won't come off. Now I just have to find the shift shaft and where it disconnects...that is obviously the problem.
 
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salvageman

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Apr 18, 2011
Messages
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Re: stuck lower unit

no, I think there is some way that they separate because the mechanic I spoke with said there is no way to take off the lower unit w/o disconnecting them....I have looked at the same diagrams you show here....on one video I watched there is a nut between the two rods and you have to back the nut down the lower one to disconnect them....I need to know whether or not I need to pull off the long cowling in the mid section or not to look for any such coupling....anybody out there have this motor?
 
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carholme

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Sep 4, 2010
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4,845
Re: stuck lower unit

Well that is why I asked for the s/n to make sure we have identified the engine correctly as the connections you describe are completely different.

Anyway, good luck!

Gerry
 
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BoatNoobie

Petty Officer 1st Class
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Jun 17, 2009
Messages
314
Re: stuck lower unit

Now I dont know how similiar it is to my 2005 60 4-stroke, but I will give you my input.

On my motor, there's 4 bolts, and 1 nut. The nut is under the anode plate.

Anyways, after I removed all those, I couldnt get my lower unit to come loose. On the left side of my engine, there's this little nook. Looks like you're suppose to use that spot as leverage to pry. Anyways, that's what I did. I had a big prybar type tool and used it to getting the lower unit loose. I had to work it slowly. I did chip the paint a little bit on the lower unit where I used leverage, but it worked.

On my motor, there's these 2 lugs I call them on the lower unit. I think they were just super tight.

Didn't have to mess with my shift linkage. They seperate with a coupler piece inbetween.
 
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Ragtime1962

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Apr 22, 2011
Messages
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Re: stuck lower unit

Sorry for jumping in without a solution- I too have the same issue. I have a 2005 150 ob. I think I may have missed a nut or bolt. I took the bolt off the front of the housing, 2 lock nuts to either side of it; the anode and bolt inside it. The housing has a gap at the rear, above the propeller, about an 1/8", but the the front won't budge. Please help, rockfish are in the bay! I appreciate any feedback. Thanks. Rick
 
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salvageman

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Apr 18, 2011
Messages
13
Re: stuck lower unit

As I said, the mechanic told me, "if you don't disconnect the shift shaft on a fourstroke, you won't get the lower unit off.....at all." (He said it's totally different on a two stroke.) Nobody wants to tell me where to access the disconnect point or how to do it because they make their livings doing stuff like this for most people. For me, with my warranty situation, I will take it to a dealer anyway just to be safe .....but don't think for a minute that I won't figure out how to do this.....after all, the warranty, for whatever it's really worth, is only good 'til 2013. I have ordered the oem service manual which will explain it all. When it arrives, I'll post the "how to."
 
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carholme

Rear Admiral
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Sep 4, 2010
Messages
4,845
Re: stuck lower unit

salvageman;

I can see this upsets you and you are listening to the mechanic wanting to believe what he says about having to undo something to release the shift shaft. It really depends on whether you have the type of shift shaft which changes gears by moving the shift shaft vertically in the lower unit or the type where the gears are changed by rotation of the upper and lower shift shafts which are splined together.

The previous drawings I sent you are for the type which rotates the shift shafts to change gears and there is nothing extra to disconnect when you have the mounting hardaware removed.

Here is a drawing of the vertical movement shift shaft from my 2000
40/4stroke:

http://www.crowleymarine.com/mercury-outboard/parts/4482_280.cfm

If you look at item 34 and 37, you will see how different they are from your engine. This is the type of shift shaft which requires that you disconnect the retainer clip inside the lower cowl before the LU can be dropped.

There is also the a vertical shift shaft movement type where the upper and lower shift shafts are connected through a threaded coupler (accesible externally) and are separated by undoing the jam nuts.

However as stated before, the s/n which you have provided is the type of shift arrangement per post #9 and if you have all the hardware disconnected, the LU is ready to come off, barring any corrosion at the driveshaft to powerhead splines, preventing it from dropping.

Hope you get it worked out.


Gerry
 
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Maxz695

Guest
Re: stuck lower unit

Thanks for the lesson on You Tube it was very informative and educational
 
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