Mercury 7.5 HP Motor Refresh (1969 model year)

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,030
Those ball bearings are a 204 bearing.--------I get a stack of them at $6.00 each.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
OK, thank you.

I am still not sure about water getting sucked into the crankcase, but it could have been.

I think my plan should be to do the following:

(1) New ball bearings

(2) New crankshaft seals

(3) New piston rings

(4) Hone cylinders

(5) New gasket set

(6) Clean/Decarb the top of the cylinder and the pistons - While the powerhead was still together, I was able to reach into the cylinders and scrape off a layer of loose carbon on each piston. They still have some carbon on them as per the picture below, but not the heavy flaky layer that was originally there.

IMG_9058.jpg

(7) Put it all back together (pray that it starts) and and give it some break-in time for the new parts.

Thoughts on this plan? Am I missing anything?
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Those ball bearings are a 204 bearing.--------I get a stack of them at $6.00 each.

I'm seeing these bearing at about $15 each. Can you share your supplier(s) ? I usually like to get more brand name bearings, like Timken,

Also, any good sources for the upper and lower seals? I would imagine that they are fairly generic. The Merc part for the lower seal is about $20 :eek:

Looks like I got to pull or press the upper bearing out of the carrier/retainer . . . any tricks to doing that? I do have a 10 ton press, but not sure how to best go at it, given that the needle bearing is right above it.

IMG_9046.jpg

IMG_9047.jpg
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,030
The ultra simple way is to use heat.----Heat the bearing housing with a small propane torch.-----Bearings will fall out.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Thanks, racerone I'll try that.

Any good sources for the parts I mentioned? (Thanks for your help on this project)
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,030
I walk next door to a starter / alternator shop.----Those bearing are $ 6.00 each.---Not sure what is in your area.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
I walk next door to a starter / alternator shop.----Those bearing are $ 6.00 each.---Not sure what is in your area.

Looks like the BL and NTN brands are about $6-7 online and the Timken brand is about $13 . . . not a big deal, either way, only need 2 of them. I think I will take the existing bearings and seal out and get the numbers and any brand markings off of them, if I can, and go from there.

Looks like the gaskets are sold individually . . . there used to be a 'kit', but that no longer seems to be available. Piston rings look like they can be had on eBay, mostly new original stock. Comes in a set of 12 rings . . . not sure why they have 12 rather than 6 :noidea:

I am wondering if there is a way or a spec for checking the original rings to see how much wear they have on them. I think that I am not getting as much compression as I should. I did a warm compression test a couple of years ago, and my recollection was that it was in the 90-100 psi range. I did one recently, just as a quick check, but the engine was stone cold at the time. Thoughts?
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Quick Update:

I have been compiling a parts list and suppliers for the parts needed to rebuild the powerhead. I inspected the lower bearing . . . it has markings of "6204" on it, which equates to the 204 bearing family. A fairly common bearing as it seems to be widely used.

The parts diagram shows a check valve and welch plug in the lower portion of the crankcase. So I assume that this is it (pic below)

IMG_9063.jpg



On the inside there is a channel that by passes the bearing and lower seal location leading to the check valve and plug. I assume this is a crankcase drain :noidea:
IMG_9062.jpg


The reason I ask is that I am noticing some signs of calcium/salt in the lower portion of the crankcase, which you can see in the picture above. Just want to cover the bases as to how water would be getting into the crankcase and on into the combustion process.

If the gasket at the powerhead base were leaking, there is a water channel right in the area where the crankshaft mate to the drive shaft, as shown in the pictures below. I assume if the lower seal is worn (which it appears to be, but intact) then it is more likely that the seal would be letting water in, rather than the check valve hanging up ? :noidea:

I did clean the check valve with brake cleaner as an added measure.
IMG_8998B.jpg


I don't see tremendous evidence of water in this area directly around the driveshaft, but would be looking for any comments. the gasket in the picture above does not look like it failed, but it could have been weeping.
IMG_8990B.jpg
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Quick Update:

I got the bearings out of the upper retainer . . . racerone the heat idea did the trick nicely :thumb: Then, I pressed the needle bearing out. The Needle is a Torrington J1210, of course Torrington Bearing is no more - became part of Timken Bearing.

I am having 1 challenge with the disassembly . . . There are 2 'keys' on the upper end of the crankshaft (they are P/N 28-20094). I got one of them out, but the other does not want to come out. I have soaked, heated, hammered, etc., but still nothing. I have worked the key down to a point where there is not much left, but it still has to come out, so I can put a new one in.

I have not wanted to get too rough with the crankshaft in terms of heating or hammering, as I assume it may not like that . . . here is a picture of the 2 key/key slots . . green is good red is not.

IMG_9074.jpg


Thoughts, ideas on getting the remains of the second key to come out ?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,030
The bearing industry standardized a gazillion years ago .---The name on the bearing does not matter.---As far as size is concerned a 1210 is a 1210 is a 1210 needle bearing.---Name does not matter.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
The bearing industry standardized a gazillion years ago .---The name on the bearing does not matter.---As far as size is concerned a 1210 is a 1210 is a 1210 needle bearing.---Name does not matter.

Yes, I am always curious what OEM suppliers the engine manufacturers used at the time. I did the same sort of thing when I did some work on my Bravo 3 outdrives.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,295
Yes, I am always curious what OEM suppliers the engine manufacturers used at the time. I did the same sort of thing when I did some work on my Bravo 3 outdrives.

They used the lowest cost suppliers, many times using multiple suppliers.

Regarding the key that won't come out, I have had luck in the past plug welding a bit of scrap metal on them, and once cooled, prying it out
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,030
I drill a number of holes in what is left using say a 1/8" bit.-----Then with a small punch on one end it basically falls out.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Quick Update:

I have drilled several holes in the 'woodruff' (?) key . . . still not budging.
IMG_9075.jpg


I did not want to drill too deep, but have been trying to get to the bottom of the key slot. I did figure that since it is the same key for both slots (according to the parts list) and the shaft is thicker in the area of the lower key, that the key slot itself is a bit deeper than the upper slot.

Anyway, I may try the torch again, now that there is less metal. Also on THT and elsewhere, I have come across a method to cut a slot in the key with a small cutting wheel and work it out by compressing it with nipper pliers. Since there is nothing protruding at this point, I may just make several cuts in the key with the a cutting wheel . . . sort of like just remaking the slot. :rolleyes:

The funny thing is that the top key came out fairly easily.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
I got the remains of the old key out . . . finally. :rolleyes:

I got some Dremel cutting wheels and made a grinding stone about the width of the key slot and ground down the remains of the key until it finally gave up and I could chip it out.
IMG_9076.jpg


The Dremel wheel was a bit bigger than needed, but I think the slot will be OK.

Next steps are to order the new parts.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
There is one other dis-assembly thing that I was hoping to take care of . . . The saddle/swivel assembly. It would be nice to get that thing to come apart.

My understanding is that the swivel pin/shaft which creates the axis point between the saddle and the swivel/clamp assembly needs to come out. The shaft is shown via the red dotted lines. During the season the salt (salt water) gets up into the lower portion of the shaft and binds it up (big time). The grease fitting (green arrow) is at the top of the shaft housing and as such not much, if any, grease gets down to the lower portion of the housing. I noticed on my 4.5 HP Johnson that there is a grease fitting on both the top and bottom of the shaft housing. I'd like to do the same here, (yellow arrow) but would probably put the fitting on the underside of the housing so as not to interfere with the steering.
IMG_9078.jpg


Here is the lower end of the pivot shaft that is pressed into the saddle housing. It certainly has 40+ years of rust and corrosion holding it in. I'm not certain if it is a press fit or is fairly loose when first assembled. Right now it seems to be the immovable object. I have been looking for the unstoppable force to get it to budge, but am concerned about breaking the saddle casting.
IMG_9081.jpg


Here is the shaft from a view of the top portion of the assembly. It looks like it wants to be either pulled out or pressed out. I have been trying to get it to turn or move in any way, but no luck so far. I see that these shafts from similar vintage motors are available as individual parts on eBay, so someone must be able to get these things apart.
IMG_9079.jpg


I have done the heat thing, the liquid wrench thing, and the lightly impacting thing but no movement so far. I don't have my big press with me, otherwise I would try that.

Any ideas? :noidea:

If I can get this apart, then I can ream the shaft housing a wee bit and install a second grease fitting. If I can't, then I'm not sure I can remedy the salt situation, which gets progressively worse as the season goes on until a point where I cannot steer with the tiller.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Well I gave up on trying to pull the swivel pin out of the saddle casting, figuring if I continued trying that I would do more harm than good.

So, I just drilled into the bottom of the swivel bracket until I hit the swivel pin and then threaded for the grease fitting. The area where I drilled into was a bit thicker than the rest of the bracket, so I was able to get a few threads cut and install the grease fitting.

IMG_9088.jpg

This grease fitting is on the underside of the swivel bracket so as not to interfere with the steering.

With the grease fittings on both top and bottom, I should be able to get enough grease in there to keep the salt water out.

Here is a picture of the now 2 grease fittings . . . the one on the left is the original and the one on the right is what I added.

IMG_9087.jpg

I have come to find out that there is a grove and channel in the swivel pin that is designed to let the grease flow down to the other end of the swivel bracket, but I could never get grease to show up at the bottom. Probably not all that effective a design.

On to the parts ordering . . .
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
I have most of the parts on order, so in a couple of weeks time I'll be putting things back together. I just need to get some of the fasteners that either broke or were drilled out during the disassembly . . . mostly fasteners of the water jacket covers on the cylinder wall and top. I was able to save the ones for the crankcase halves.

Questions that I have at this point:
1) For the cylinder top cover, I believe they are a fine thread. . . should I get SS fine thread hardware/w nylocks for those replacement fasteners ? or just go with regular steel fine threads ?

2) For the cylinder side covers, I need to match the existing size/thread, but wondering if I should also go with stainless steel ???

3) On the crankcase halves - my reading tells me that I need something like 'Loctite 5188' flange sealant for the mating surfaces . . . would that be correct, or any advice there?

for the wear parts, I am replacing

Upper and lower shaft seals
Both upper and lower ball bearing (204's)
The needle bearing (1210)
Piston rings

I plan on leaving well-enough alone for the connecting rod bearings

4) As I put this all back together, I am assuming that I should use fairly liberal amounts for 2-cycle oil as I insert the pistons and new bearings, etc. much like one would do when re-assembling a 4-stroke engine? or is there a better approach ???

Thanks in advance to any and all who can help me with these questions or add comment to my approach on parts and assembly. :hail:
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
I have received most of the parts for rebuilding the powerhead. . .
IMG_9127.jpg

I just need some flange gasket maker and maybe a few other pieces of hardware.

Some of these parts look like NOS, based on their packaging, etc. . . . other parts look fairly recent.

I ordered some 18-8 stainless (304) hardware to replace the hardware that I had drilled out or otherwise destroyed. I could not find a good match for the powerhead machine screws ( 1/4" - 28 UNF), which appear to be Fillister heads. So, I went with socket heads instead. I may still need some thin washers, because the socket heads are a bit more narrow than the Fillisters.
IMG_9129.jpg

IMG_9131.jpg

I also got some 1/4" - 20 hex bolts for the side water jacket cover, which are fine.
 
Top