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After a year in the making the three center main bearings have been completed. The first picture is a pair of 60-66 inch inline cranks. The first crank for the 6 cylinder in the Mark 75's had a single row of needles in the main. The later cranks had a double row of needles and used the same shell and rollers in all the inline 6's till the end of their production. The single land between the double row of needles and its clearance with the shell made the seal between the cylinders. A labyrinth type seal from the oil, like a reed block but without groves to hold more oil. That said, the old style crank had a double seal, two lands. To make the bearing work, I had to incorporate the lands in the bearing shell to make the seal and to retain the end play of the roller.
The process was to machine the bearing in one piece and heat treat. After they were heat treated the ends were ground to size. Then cleaned the OD by grinding to a common oversize OD. They were then chucked and the inside roller thrust faces were ground to the correct size. That would be the roller end play dimension. After those operations were completed, the bearings were cut in halve with wire feed EDM. Now we were able to chuck the halves, which had numbers etched in the ends so they were not switched or reversed, in a 6 jaw chuck on an ID grinder. By indicating on the ends to insure no step in the roller thrust face and indicating the OD to have the same readings, due to the appox .010 removed by cutting, at the cut line and 90 degrees for centering. The ID of the seal face and the ID of the bearing runway were ground to size. Long winded process. Now we were ready to grind the OD. For that process I made a mandrel to run in a center-less grinder. The end of the mandrel had a land turned to the shell roller surface size and rare earth magnets inserted 180 degrees apart. These locked the shell halves to the mandrel along with a cap on the end of the mandrel to clamp the shells against one of the roller thrust faces. This also reduced the possibility of the shell rotating on the mandrel. Turned the OD to size and cut groves in the OD for spiral lock rings.
I had concerns about the getting the spiral lock on the crank, but they threaded around like putting a key on a key ring. They will be placed on the crank first and then the loaded halves will be placed between them and then snapped around the bearing.
Was a long and trying process, but came out as I had hoped.
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Time for a progress update. I have completed the patterns for the tower housing and power head to housing adapter which has the upper pivot boss added. I also patterned the lower pivot boss which will weld to the gear housing.
I have attached photos of the finished patterns and they have been taken to the foundry.
I will now, with all parts completed and checked out, start a trial assembly of the complete power head.
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I have attached photos of the lower unit as it has been cut for attachment of the lower pivot shaft boss. Sad to cut a virtually new unit, but had to do to complete my goal. The wood pattern is placed in the weld position. The front cut out is still nearly 1/2 of an inch in front of the water passage that comes up under the water pump base forward of the drive shaft. The weld will only be in and forward of the water passage and the extensions of the casting to the rear are pressure pads that align with the solid part of the gear case between the drive shaft cavities. I will remove the forward drive shaft to shorten and re-cut the spines. Welding and machining will be done then.
The need came for a new clamp bracket. The boat has a 90 degree transom and the standard clamp swivel bracket assembly on a 90 degree transom will not allow the engine to adjust parallel to the water let alone the required 6 degree tuck under. You can see in the drawing that I let the swivel bracket pivot on the tilt adjust pin 8 degrees back to a new tilt pin location. That adjustment is made in the new clamp bracket.
Have assembled the crankshaft with the main bearings and the rods. Just got the spiral lock rings for the wrist pin keepers, so I can hang the pistons. The spiral locks for the main bearings were placed on a surface grinder and ground to a tight fit in the bearing race grooves. I then made a socket mandural on the lathe and ground the ID of the locks to match the shell groove diameter. This was done to provide a perfect, if there is such a thing, alignment vertically of the two halves. These were cut with EDM and not broken like OEM bearing races. The rings were then loaded on the crank and then the loaded shells between the rings. Then the rings were loaded up into the grooves and lightly tapped into the grooves for positive seating.
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Dick, if any situation or project justified messing with a speedmaster like this, THIS would be it. Awesome. Out of curiosity what generation/year is this speedmaster?
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The unit was purchased new from Mercury in 1970 or 71. I bought 2 left hand units that I was going to use on the rotary valve motors that I was working on. This one ran maybe 8-10 laps. The other is still hanging on the wall untouched as it came from Mercury. Paid 620.00 a piece back then. They are twin pinions. That is why I am using it on the 100 inch motor.
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I guess we are at the point where a picture is worth a thousand words. I am now in the test assembly and will do final fitting of the perifferials that will complete the powerhead. the electrical, fuel system and linkages. Next few posts will be just pictures.
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Just Outstanding
The workmanship is second to non not withstanding the outstanding engineering. It will be a true thing of beauty when it is running on the water. Can't wait to see the finished product. Also love the lower unit/tower housing work.
Alan
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Looking very good, we all can not wait to see you on the water with this project.
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I assume you're satisfied with the fitting? Truly awesome work. This was the moment I have been waiting for (other than it firing in the future). Also see a very cool original looper 6 on a 75H tower ;)
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Once your project is finished it could be made into a college course with three semester hours plus a lab. Engineering students would enjoy this class I believe.