1988 70HP Mercury Lower Unit

[bwhalerman]

Wow, this is an incredible offer. It is much more than i would have ever expected. I have learned quite a bit in this process so while I wish it was all over and ready to go I can't deny the importance of getting hands on experience. You can only read so many books and then it's time to let good old experience do the teaching. I have made some notes of cautions to take and have a print out of the schematic so i have visual aids nearby. My objective is to get the shift shaft back in place and to free my magnetic wand from the shift tube

What is the general rule for reinstalling the lower unit. Should the helm control always be in neutral before removing the lower unit? And when reinstalling the lower unit as long as the shift shaft hasn't been fiddled with the reinstall should be good to go? I learned one valuable lesson and that is never let the shift shaft come out of the cam!!!

Thank you very much for all of your good advice.

 

[Texasmark]

First thing I would do would be to clean out the interface of he LU and mind section shaft/collar. Then lube them up with a thin layer of grease, none on the top of the shaft....same with your DRIVE shaft when installing it. Grease on the top can inhibit fully seating....per the book.

I like N because in finding it....moving your cam back and fort using a pair of vise grips on the shaft protruding out of the LU when all is ready to install back in the midsection, you are able to feel F and R and know that you are in the center....no guessing. Other thing is I like N because you can rock your remote control shifter back in forth in N and ensure that your shift alignment is what it should be.

Some like F because in F you can twist the prop to get the DRIVE (all caps to ensure you pay attention that I'm not talking about the prop shaft this time) shaft to twist enough to get the splines to line up with the power head splines so "the last half inch" required in mating the LU to the MS gets closed. For that alignment, since I prefer N, I just move the flywheel with a slight force on the LU till you feel it budge then tighten the nuts evenly to bring it up..do not force it, it should go up with slight pressure.....oh and ensure that your water tube is reasonably straight and it gets in the cooling hole in the bottom of the block. To me that's the hardest part of al because it's hard to see up there from the LU. But on my '02 engine Merc finally put a bracket and tube extension down at the interface, adjacent to the shifter connection where the water tube is captivated and essentially mates itself.

Agree on being careful when separating so that you don't have to go through what you are.

However, every cloud has a silver lining doesn't it.

Well sir, yours is two fold....seeing what moves when you activate your shifter and how power is transmitted from your engine to your propeller, and the BIG one is that your engine is a 1988 and it's a good excuse to change out seals that are long due for a change......saves your having to do it later when the time might not be right. The only other seals to the lower unit are under the water pump and on a lot of engines the seals are part of the water pump lower housing; when the water pump comes out so do the seals.

Thanks for the compliments. I enjoy the exchange when I get to work through problems with folks....keeps my mind active.

 

[bwhalerman]

When i purchased the 17' Montauk in Dec 2014 the sea trial was good, compression test was good...but I knew some PM was ahead of me. But that's okay because I bought a classic boat that was exactly like the one I purchased new in 1983. I got this in excellent condition for $8k.

Last year I replaced rectifier, starter, solenoid. Over the past 3 months I experienced some issues with the motor bogging down, sometimes stalling and hard to start and the last is the horn went off. Figured it was an overheat issue as the oil injections system is no longer on the motor. I decided to pull the water pump. Replaced the cover plate and seals, gaskets, new impeller. Clearly this had not been done for some time. All kind of mud and gunk. Also replaced all the fuel lines, primer bulb, the fuel connection clip at the motor connection and that connection as well. Rebuilt the fuel pump.

Now that I'm this deep into PM stuff I decided to replace the thermostat and the popplet. I know the thermostat may not be bad but with the horn sounding I figured that too could be a future problem so buckle down and take this step as well. All of my parts for both jobs should arrive by tomorrow.

I'm not really all that upset about what I'm about to undertake. As you mentioned it is better to fix it when convenient. It's like running out of gas in front of the gas station It all works out.

 

[Texasmark]

When i purchased the 17' Montauk in Dec 2014 the sea trial was good, compression test was good...but I knew some PM was ahead of me. But that's okay because I bought a classic boat that was exactly like the one I purchased new in 1983. I got this in excellent condition for $8k.

Last year I replaced rectifier, starter, solenoid. Over the past 3 months I experienced some issues with the motor bogging down, sometimes stalling and hard to start and the last is the horn went off. Figured it was an overheat issue as the oil injections system is no longer on the motor. I decided to pull the water pump. Replaced the cover plate and seals, gaskets, new impeller. Clearly this had not been done for some time. All kind of mud and gunk. Also replaced all the fuel lines, primer bulb, the fuel connection clip at the motor connection and that connection as well. Rebuilt the fuel pump.

Now that I'm this deep into PM stuff I decided to replace the thermostat and the popplet. I know the thermostat may not be bad but with the horn sounding I figured that too could be a future problem so buckle down and take this step as well. All of my parts for both jobs should arrive by tomorrow.

I'm not really all that upset about what I'm about to undertake. As you mentioned it is better to fix it when convenient. It's like running out of gas in front of the gas station It all works out.

"You did good" as the sayin goes. This ought to fix you up with having to do PM for quite awhile.

 

[bwhalerman]

Oh boy!!! Lots and lots of parts arrived today. Felt like Christmas and then reality struck. I gotta do this tomorrow. And the I panicked and realized I need to put some beer in the refrigerator lol.

 

[Texasmark]

Oh boy!!! Lots and lots of parts arrived today. Felt like Christmas and then reality struck. I gotta do this tomorrow. And the I panicked and realized I need to put some beer in the refrigerator lol.

Sounds like you have your priorities in order. Grin Will be standing by tomorrow off and on.

 

[bwhalerman]

Step 1 was finally successful. It took awhile but I was able to remove the carrier from the lower unit. One goofy thing I need to do is to remove my flexible magnet shaft that got stuck down the shift shaft tube.

 

[bwhalerman]

The prop shaft is out. I inspected the reverse gear and thrust bearing. All are in good shape. I have the all the parts out up to the ratchet. Now I see the drive shaft inside the gear case engaged with forward gear. When I look down the shift shaft tube I'm seeing the top of a cam (i guess) with a dimple in the top of it.

My question now is how to I restore neutral and reinsert the shift shaft?

 

[Texasmark]

If the F gear is in your way, get a right angle pic and catch the side of it and work it out (about 1") and it will fall to the bottom of the housing where you can fish it out. Then you have access to the cam. With the SHIFTER shaft pulled out, the cam should come straight out.


My question now is how to I restore neutral and reinsert the shift shaft?



The shaft should be symmetrical on both ends, no need for it to not be (opinion). Pull the shifter cam out and look at it. With the shaft out it should just pull straight out.....the shaft is what holds it in position.

Once you have looked at it and observed how the detents are a different distance from the shaft hole (pivot point), pick up the prop shaft and look at the front of it. The "cam follower" is the somewhat pointed, conical, cylinder at the front of the prop shaft. Push in on it and observe the "clutch dog" (the gear which is riding on the prop shaft with a pin through it, sitting on a large spring. As you push in the dog should move toward the prop end of the shaft. This is what your cam does and in doing so it moves the dog from the rear of F gear to N and on to the R gear as the cam is rotated.

Put the cam back in and position it such that the detent that is closest to the pivot.....position that would exert the least pressure on the cam follower on front of the prop shaft.

After you get everything back and buttoned up, with a pair of vise grips (I like to use) twist the shifter shaft cw as I recall to move into the N notch and while rotating prop shaft, on to the R position. The prop should click as you rotate it CW viewed from the rear and turn the DRIVE shaft when turned CCW. In N it spins both directions freely, and if you had square slots and cogs on the R gear, as you are turning the prop shaft, when a set of these line up it will slide into R and lock up turning the DRIVE shaft in both directions. If you had the sawtooth arrangement then it acts like F gear, lock CW and spin CCW.....just the opposite of F gear.

 

[bwhalerman]

No Title

It may be that I'm not properly explaining what's happening (bear with me I'm visual plus learning a new language ) I am a bit confused. And some of it comes from what I see coming out of the gear case versus what is on a schematic.

The first photo shows all the parts that came out when I pulled the carrier. the 3 balls probably came out and were laying on the housing. When i compare what came out of the gear box to the schematics I am looking at http://www.crowleymarine.com/mercury-outboard/parts/365_180.cfm?mdl=7EB3DW they are showing parts that I didn't see when disassembling. I didn't see a spring. I didn't see the pin with the hole in it (referred to as follower kit cam. I just saw the parts in the first photo.

The second photo shows the drive shaft coming into the top of the carrier. I assume that is in contact with forward gear? Next as I look down the shift shaft I see the top of a cam I guess with the dimpled surface.

 

[Texasmark]

It may be that I'm not properly explaining what's happening (bear with me I'm visual plus learning a new language ) I am a bit confused. And some of it comes from what I see coming out of the gear case versus what is on a schematic.

The first photo shows all the parts that came out when I pulled the carrier. the 3 balls probably came out and were laying on the housing. When i compare what came out of the gear box to the schematics I am looking at http://www.crowleymarine.com/mercury-outboard/parts/365_180.cfm?mdl=7EB3DW they are showing parts that I didn't see when disassembling. I didn't see a spring. I didn't see the pin with the hole in it (referred to as follower kit cam. I just saw the parts in the first photo.

The second photo shows the drive shaft coming into the top of the carrier. I assume that is in contact with forward gear? Next as I look down the shift shaft I see the top of a cam I guess with the dimpled surface.

Picture on the left: Immediately in front of R gear is the Clutch Dog. It 's forced along the prop shaft to do the actual shifting. Pull it off the shaft (pay attention as to which end it forward and all...teeth have to match the gear teeth when you put it back) and look at it, rolling it around and look for a thru-hole. Also observe the diameter reduction around the center (where the hole is located). This is a groove for the retaining spring (Item 49) which keeps the pin from falling/flying out of the dog.

You are supposed to have a pin (Item 48) go through that hole to lock the dog to the adapter which is part of Item 45, the adapter is to the right of the spring (Item 46) which also has a hole in it. If you don't lock the dog to this adapter, you can't shift....the dog will just float along the PROP shaft and who knows where it will be at any given time.

The spring, (Item 49) should still be up inside the hole where the follower and balls fell out, or it too is missing.
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Backing the truck up, how did this engine shift before you started working on the lower unit, this time?
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Pic #2 is the drive pinion, attached to the DRIVE shaft, and behind that is F gear. Visible through the hole in F gear is the shifter cam. As I said earlier, fish F gear out of it's bearing retainers and slide it under the pinion. It may take a bit of wiggling and all but I have removed it without removing the pinion on a different lower unit.

When you get the cam out, get me a picture of it, top and front view, please.

Will be in touch, about every 30 minutes.

If I didn't adequately answer your questions point me to where I missed what you need to know.

 

[bwhalerman]

I think I'm getting a bit closer to understanding. I put the shift shaft in the tube. When I looked into the gear housing Photo number 2 I then saw the spline on the end of the shift shaft. Before I pulled the carrier out and looked in from this view I didn't realize that when I looked down the shift shaft tube I was actually seeing the bottom of the opening in which the shift cam sits. I used my handy dandy magnet and found the cam. I slid it into place and then inserted the shift shaft. Now that I see how this works it makes so much more sense to me.

Now the secondary issue. When I look at what came out when I pulled the carrier it doesn't correlate with the diagram I got out of my manual. In my manual it shows items in the following order from jaws at the end of the shaft toward forward gear. What am I to believe?

1. Jaws
2. Spring
3. Guide Block
4. 3 metal balls
5. Cam follower

When I pulled the carrier I saw the following:

1. Jaws
2. 3 metal balls
3. Cam follower

 

[Texasmark]

Jaws you refer to is Item 47 I assume? If not what?

Item 47, the "Guide Block" which I refer to as the "Clutch Dog" has to be locked to the Cam follower movement.....period. This is how you shift. The spring, Item 49 just maintains pressure against the cam so that the dog remains engaged or centered (for N).

First off if you didn't find any loose/possibly chewed up parts, other that the cam, One has to assume it came that way.......assuming that the PO or a service department hadn't been in the LU and didn't return these parts. If the manual omits these parts then they must be omitted. If you have been shifting this engine satisfactorily, then they are omitted in your particular model. If that's the case, forget about it and let's move on.......however:

Mechanism, mechanism.........how does the cam movement, which pushes on the cam follower (pointed object on the right in Item 45A) , against Item 49's spring pressure) as you move from F gear to N and onto R with the cam physically moving everything inside the PROP shaft to the rear including compressing the spring.........cause the clutch dog to move from engagement with the rear of F gear to the neutral position on back to engage the slots of R gear if the contents of the prop shaft aren't physically connected to the Clutch dog?

Open for your reply to this as you have the pieces in your hand.

Edit: I missed the fact that you said you have the cam in place, pinned properly and it functions....you can see the 3 detents move past the hole in the center of F gear where the end of the PROP shaft rides when you rotate the shaft. That's great. Solves that problem.

 

[bwhalerman]

No Title

I didn't remove 47-49 the are still on the prop shaft. So the spring is embedded at the end of the shaft and inside 47-49? Is that Right? I decided to leave most things intact before I completely understood what I'm doing. The reverse gear looks very good. All teeth are in good shape. I left the spring and pin intact also.

At this point the only replacement I have done is the O ring that fits on the reverse gear. I inspected the bearings and this also move freely and are well oiled. If understand, at this point I could reinstall the prop shaft if i put the 3 metal balls inside the ratchet then install the follower kit? But, I didn't see the guide block. I assume that is also inside the 47-49 configuration with the pin through it?

The first picture shows the shift shaft installed in the cam. The second photo is the cam I retrieved. I inserted the shift shaft after installing. and the last picture is what came out when I pulled the carrier out.

It shifted fine before I pulled it out. So, I'm assuming the notes I made above means everything is intact.

When I started today I didn't think I was going to be successful getting the carrier separated from the LU. I sprayed WD40 in bolt holes and around the casing. Let it sit for an hour. I held a 1/2 ratchet extension on the side of the bolt area. A couple smart whacks on the extension with a rubber hammer and it loosened. The used a long screw driver to gently pry it out.

 

[Texasmark]

Ok. If everything worked, then who are we to argue.

Are you going to change your prop shaft seals? You ought to be able to grasp R gear and pull everything out of the carrier so that you can get to the seals. Just slide it out the way it is and when finished slide it back. The seals are back to back with the flat side of the outer out and the flat side of the inner in....the open areas, where you can look in and see the springs are facing each other.

Finishing up.

1. Looking as pic 1 is viewed, twist the shifter shaft till you are looking at the center hole. You will want your cam follower to slide right into that slot upon reassy. Don't move the shaft when reinstalling the LU to the midsection and ensure that your remote is "jiggled" to get the slack out and ensure you are centered on N. Then, upon reinstalling the LU, you can eyeball line up the SHIFT shaft coupling and the water tube and when you get to the last ? to 1" and things stop, just keep slight upwards pressure on the LU and slowly rotate the flywheel till the LU slides into place. On some LUs you have to keep tweaking the nuts on the side of the interface since there isn't much room for vertical movement.

2. Slide the prop shaft out of the carrier and change the seals, lubing the lips and the manual may stipulate thread sealing compound. Red was in my manual but I use Blue for everything as you can get it out without any problems....then lube the lips and when you slide the PROP shaft back in, wrap some paper around the prop nut threads so that they don't cut into the seals as you slide things back together.

3. Tilt the LU with the front up, balls and Cam follower back in the shaft, Oring on the bearing carrier lubed, mating surfaces cleaned up, insert the carrier assy with your mounting screws handy. You will have to push against the cam follower spring (Item 49) so you might just get the 2 mounting screws in place and let them draw it up....should go smoothly and wouldn't hurt to rotate the PROP shaft while installing. Should not be any binding. When you get where you are starting to compress the spring, you might give the flywheel a bit of a turn to ensure that the pinion lines up with R gears.

4. Run a check ensuring that FNR work correctly and leave in N when finished.

5. Thrust washer on, ensuring that you match the slope in the PROP shaft to the slope in the ID of the thrust washer, and prop on.

6. LU upright, fill with gear oil,

7. Mount her up.
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I know this is overly simplistic but it gives you a checklist .....may come in handy with the exuberance of finishing the job. Would for me.

 

[bwhalerman]

Okay this is where I'm at.
1. the carrier is bolted to the gear case the prop is still in forward gear. if i rotate clockwise it clicks. Next I stop it before it clicks again. As i understand it do I now turn the shift shaft CCW until it denents 1x then 1 more CCW turn until it dentents again and then one more time until the same happens? Then I can go clockwise to get the gear back in neutral then reinstall and to boating

 

[bwhalerman]

By golly Ed I think I finally got it. I reinstalled the carrier and the it was in FWRD gear. I turned the prop slightly CW just before the click. I then rotated the shift shaft CCW until detent the the prop spun freely. Turned CCW one more time and it was in reverse. Turned CW to get it back into N, the prop spun freely. Looks like I'm ready to grease 'er up and rebolt to the mid section.

This has certainly been a learning experience. I am greatly appreciative of all your help and now fully understand the gear case mechanisms. I'll post back after I get it all assembled. Next step is to get it to the boat ramp and adjust the total carb rebuild I did. It did start right up the last time so I think with a few adjustments it should be good to go.

 

[Texasmark]

Outstanding. Keep us posted.

 

[bwhalerman]

Pleasure boating is such great fun!!! Put the motor under power with water connection. New water pump job is okay, prop job is okay-FWRD, NETU, REV all work perfectly. Now the new problem is the horn went off. I suspected it to be either the thermostat, popplet or the sensor. But due to heat build up I'm suspecting thermostat and/or popplet. I'll replace them this week.

Fortunately, I had the cowling off the motor as I am also doing the preliminary carb adjustments (rebuilt them a couple weeks ago) and as I approached the motor I could see that the bendix in the starter was spinning full speed. Apparently, it didn't disengage. Could that have caused the heat horn to go off? I replaced the starter last year with an OEM Mercury.

Do you have any thoughts? I'll do the thermo and pop replacement anyway.

 

[Texasmark]

Pleasure boating is such great fun!!! Put the motor under power with water connection. New water pump job is okay, prop job is okay-FWRD, NETU, REV all work perfectly. Now the new problem is the horn went off. I suspected it to be either the thermostat, popplet or the sensor. But due to heat build up I'm suspecting thermostat and/or popplet. I'll replace them this week.

Fortunately, I had the cowling off the motor as I am also doing the preliminary carb adjustments (rebuilt them a couple weeks ago) and as I approached the motor I could see that the bendix in the starter was spinning full speed. Apparently, it didn't disengage. Could that have caused the heat horn to go off? I replaced the starter last year with an OEM Mercury.

Do you have any thoughts? I'll do the thermo and pop replacement anyway.

If you were in the driveway on muffs, you may have had inadequate pressure to make the engine overheat. A solid alarm is OT if you have a modulation module which goes 10101010 for oil and 11111111 for temp. Temp of OT alarm in normal operation is 195F for powerhead water temp. Stat should open at 143F. Poppet is for over 2500 rpm. If you haven't changed them on a new to you engine then yes that would be a good idea.

ON the starter spinning, sounds like the solenoid is welded internally. As they age, the contacts pit and in pitting the area to carry the 100+ amps to start gets smaller and smaller and finally it gets small enough to generate enough heat and welds together. Easy to test. Turn the engine off and put an ohm meter across the ⅜" studs on the solenoid. If shorted with no power then yes. If it's not shorted, your key switch may be bad keeping power to the solenoid (2 small terminals) when in the ON position when it should only be applied in the START position.

On the carb adjustment, final tweak is when you hammer down on the throttle from idle, in F gear, on the water. If it takes it you are good to go. If it bogs or hesitates, open your low speed jets like 1/16 of a turn at a time till it takes the throttle.