Dropping lower unit

[plum plug]

Let me start by saying I do have some mechanical ability. That being said I could use some direction having never dropped a lower unit on an outboard motor before. I have a 1976 Mercury 650 that I would like to replace the impeller on. Can someone give me step by step PLEASE?

 

[Chris1956]

Re: Dropping lower unit

I have never worked on a 650 before, however, they should be similar to an 850. First put the motor into neutral. Now, you should see 5 nuts above and on the underside of the Antiventilation Plate. There is also a hidden bolt under the zinc anode. Stick a thin walled 1/2 socket into the hole above the zinc anode and remove the bolt. If the bolt has been replaced over the years, it might be a large allen head bolt.

Now remove the 5 nuts. These are removed with a 9/16" wrench, however, the two in the front top will not remove until the gearcase drops a bit. Wiggle the gearcase unti it drops, remove the final two nuts, and that's it! Try not to disturb the shift shaft position, and she will bolt back up. Replace the waterpump impeller, wearplate and all gaskets. Grease the driveshaft and shift shaft splines.

You will need to turn the flywheel by hand when installing the grarcase, to line up the splines. Wiggle it back on. Do not force it with any tools or by using the nuts, or you will likely damage the crankshaft.

I recommend a service manual

 

[Jacket4life]

Re: Dropping lower unit

Not being a smart ace at all:

Step 1: Buy a manual. I have the Clymer, it's about $30. The Seloc is about the same. The factory is about $60, but MUCH more detailed, it is my next boat purchase. IF you aren't willing to pay $30 for a manual, selll the boat or take it to the shop when you need something done, as you will do more harm than good just poking around on an outboard engine with no knowledge. Seriously, it is MUCH better than asking for instruction on here, and it has pictures. This forum is best suited for answering common questions and trying to help with odd/infrequent occurences through pooling of knowledge.

That being said, I will try to help you:

1. Remove the trim tab (right above the prop) Before you remove it, make some kind of mark so you know where to put it back. (It's not straight, if you will notice...)

2. Remove the nut that is hidden by the trim tab. Yes, many have not know this and done irreperable damage while trying to remove a unit while it was still there.

3. Remove the nut forward of this nut.

4. LOOSEN the two nuts at to front of the lower unit to the top of the threads on the studs. Wiggle the lower unit until it "drops down" onto these nuts. The reason you do it this way is because they sometimes stick, and if you have to put more force on it, you don't want to hurt yourself of the lower unit when it flies off.

5. After it drops down, remove the nuts and then slide the lower unit off.

6. If your engine has reverse lock, remove the plastic seelve at the top of the driveshaft. Look at it first so you know how to put it back.

7. Remove the washer at the top of the impeller housing.

8. Remove the nuts holding the water pump housing.

9. Remove the housing. Check the wear plate. If it looks like #@%&, replace it.

10. Slide the impeller up the shaft. You may or may not have to remove the impeller key to do so. I did not. If you are going to go deeper (into the actual water pump, you will have to remove it. YOu may want to remove it anyway, it's pretty small.

11. Check the wear plate below the impeller, see #9.

12. If you are stopping there, re-install the new impeller. Make sure turning the impeller turns the drive shaft.

13. Reverse your steps up to installing the lower unit. Grease the top of the driveshaft (the splines) and the shift shaft. DO NOT turn the shift shaft while you have the lower unit off. (If you want to know why, look up my thread titled forward/reverse backward. Title should tell you plenty about why to leave it alone!) Before installing it, I would also reccommend you blow through or run a small piece of 14 gauge wire through the outlet tube from the tell tale back through the water tube. A lot of time there are bugs/dirt dobber residue/crap in this hose.

14. When you are installing the lower unit, MAKE SURE you don't force anything! If you do it right, it slides right in. If you force it, you WILL break something. You may have to lower it back down and turn the drive shaft SLIGHTLY to align the splines. BE PATIENT. My first time, it went directly back on, second time took 20 minutes.

15. After installation, replace lower unit lube. The proper way to do this is to remove the vent screw (the top screw on the side of your lower unit labeled 'vent'), remove the bottom screw (labelled 'drain'). Pump lube into unit until it overflows out the top hole. Re-install the top screw. Then install the bottom screw as quickly as possible. Yes, you will lose a LITTLE. If it ALL runs out, try again. Do not try to fill it without the top screw removed, you will overfill it leading to larger problems. This is one of the few things I buy into the factory part issue, I use the quicksilver lower unit lube. It's $9 a quart in TX, but I have heard too many ppl. complain about lower unit problems when they used something cheaper. My 50 holds about a pint, so I'm guessing your 70 isn't much higher than that.

I probably left something off, but I know that's basically it. Best of luck to you!

 

[Jacket4life]

Re: Dropping lower unit

I have never worked on a 650 before, however, they should be similar to an 850. First put the motor into neutral. Now, you should see 5 nuts above and on the underside of the Antiventilation Plate. There is also a hidden bolt under the zinc anode. Stick a thin walled 1/2 socket into the hole above the zinc anode and remove the bolt. If the bolt has been replaced over the years, it might be a large allen head bolt.

Now remove the 5 nuts. These are removed with a 9/16" wrench, however, the two in the front top will not remove until the gearcase drops a bit. Wiggle the gearcase unti it drops, remove the final two nuts, and that's it! Try not to disturb the shift shaft position, and she will bolt back up. Replace the waterpump impeller, wearplate and all gaskets. Grease the driveshaft and shift shaft splines.

You will need to turn the flywheel by hand when installing the grarcase, to line up the splines. Wiggle it back on. Do not force it with any tools or by using the nuts, or you will likely damage the crankshaft.

I recommend a service manual

OMG, I am a dumbace....I kept dropping the unit out and turning the drive shaft by hand until it lined up. That is SO much easier. Funny how some things don't occur to you when you are new to something!!!

 

[plum plug]

Re: Dropping lower unit

Thanks for your help. I got the lower unit off without a hitch and found the impeller was shot. Also found a crack in the tell hose. Other then that things look great. I cleaned out the impeller pieces from the pump and tomorrow a new impeller goes in. Thanks again.

Step 1: Buy a manual. I have the Clymer, it's about $30. The Seloc is about the same. The factory is about $60, but MUCH more detailed, it is my next boat purchase. IF you aren't willing to pay $30 for a manual, selll the boat or take it to the shop when you need something done, as you will do more harm than good just poking around on an outboard engine with no knowledge. Seriously, it is MUCH better than asking for instruction on here, and it has pictures. This forum is best suited for answering common questions and trying to help with odd/infrequent occurences through pooling of knowledge.

That being said, I will try to help you:

1. Remove the trim tab (right above the prop) Before you remove it, make some kind of mark so you know where to put it back. (It's not straight, if you will notice...)

2. Remove the nut that is hidden by the trim tab. Yes, many have not know this and done irreperable damage while trying to remove a unit while it was still there.

3. Remove the nut forward of this nut.

4. LOOSEN the two nuts at to front of the lower unit to the top of the threads on the studs. Wiggle the lower unit until it "drops down" onto these nuts. The reason you do it this way is because they sometimes stick, and if you have to put more force on it, you don't want to hurt yourself of the lower unit when it flies off.

5. After it drops down, remove the nuts and then slide the lower unit off.

6. If your engine has reverse lock, remove the plastic seelve at the top of the driveshaft. Look at it first so you know how to put it back.

7. Remove the washer at the top of the impeller housing.

8. Remove the nuts holding the water pump housing.

9. Remove the housing. Check the wear plate. If it looks like #@%&, replace it.

10. Slide the impeller up the shaft. You may or may not have to remove the impeller key to do so. I did not. If you are going to go deeper (into the actual water pump, you will have to remove it. YOu may want to remove it anyway, it's pretty small.

11. Check the wear plate below the impeller, see #9.

12. If you are stopping there, re-install the new impeller. Make sure turning the impeller turns the drive shaft.

13. Reverse your steps up to installing the lower unit. Grease the top of the driveshaft (the splines) and the shift shaft. DO NOT turn the shift shaft while you have the lower unit off. (If you want to know why, look up my thread titled forward/reverse backward. Title should tell you plenty about why to leave it alone!) Before installing it, I would also reccommend you blow through or run a small piece of 14 gauge wire through the outlet tube from the tell tale back through the water tube. A lot of time there are bugs/dirt dobber residue/crap in this hose.

14. When you are installing the lower unit, MAKE SURE you don't force anything! If you do it right, it slides right in. If you force it, you WILL break something. You may have to lower it back down and turn the drive shaft SLIGHTLY to align the splines. BE PATIENT. My first time, it went directly back on, second time took 20 minutes.

15. After installation, replace lower unit lube. The proper way to do this is to remove the vent screw (the top screw on the side of your lower unit labeled 'vent'), remove the bottom screw (labelled 'drain'). Pump lube into unit until it overflows out the top hole. Re-install the top screw. Then install the bottom screw as quickly as possible. Yes, you will lose a LITTLE. If it ALL runs out, try again. Do not try to fill it without the top screw removed, you will overfill it leading to larger problems. This is one of the few things I buy into the factory part issue, I use the quicksilver lower unit lube. It's $9 a quart in TX, but I have heard too many ppl. complain about lower unit problems when they used something cheaper. My 50 holds about a pint, so I'm guessing your 70 isn't much higher than that.

I probably left something off, but I know that's basically it. Best of luck to you![/QUOTE]

 

[Jacket4life]

Re: Dropping lower unit

Congrats! It's always good when it works out! Glad you got it done with no problems! Really can't say enough that if you're gonna work on it alot yourself a manual is invaluable!

Best of luck in the future!