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Thread: Mercury Rod Cap Alignment
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11-06-2017, 02:29 PM #315000 RPM
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Thanks.. I gathered as much and why I'm not using the new bolts I bought because I torqued them once and will toss them..
This seems a bit odd, the service manual calls for a 30LB torque on the bolts, which does seem normal, however, the manual goes on to state that after 30lbs of torque tightened the bolts another 180 degree turn. I didn't do that, I only tightened them another quarter turn after 30lbs to check alignment. I did try one 30lbs then another 180 degrees tight, seems like I felt the bolts beginning to stretch, just didn't feel right.
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11-06-2017, 04:01 PM #32
That's exactly what they are deigned to do, or maybe better put it's what they do..... Stretch.
Most bolts you torque will stretch. Actually it's a more accurate way of being sure the clamping force is correct, is to measure the stretch of the bolt vs the actual amount of torque applied to the bolt.
Trick is you have to be able to access both sides of the bolt to measure the amount of stretch. Bolts that are buried in what it's clamping with no access to the back side, your left with torque spec's or torque spec's and degree of added turning past the initial torque spec...
Some are use once and toss, some are not.
OE fish motor bolts are a one time use.Last edited by W2F a V-King; 11-06-2017 at 04:04 PM. Reason: spel chc...old fingers kant tipe
James H. W2F a V-King... Want 2 Fly a V-King
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11-06-2017, 06:21 PM #33
A train wreck of mis-information on this thread ...
Random thought's ...>
When they bolt the cap in place to final size the housing bore at the factory , it's torqued to spec.
Torque to angle was brought about because 'breakaway friction" is much less @ 30 ft/lbs than @ full torque .
I like molly paste .
Most specs call for 30 wt or equivalent .
Never seen a spec that called for 180* after initial load .
Initial load plus 90* is standard .
There is a first for everything.
Mushy feel ... is usually just that .
Overtightened fasteners affect , the bolt , the female thread , the housing bore concentricy .
Motor's are like newborn's , gotta watch em real close ...
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11-06-2017, 06:49 PM #34Screaming And Flying!
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Merc 90 hp 2 style rods. Early type had threads in the rod end only. The cap had no threads. Latter style had threads on both parts. Tell me Batman.... when ya 30+ 90% do you think the rod bolt streachs in the parting surface? Or are we just too lazy at Merc to use Red.
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11-06-2017, 07:43 PM #35
Most torque plus angle is used on torque to yield bolts. The initial torque is to bring the bolt to its maximum yield point then the extra 90 degrees is to bring it into the center of its plastic phase (stretch point) once it's reached this point it will never return to its original state, thus the reason you shouldn't reuse them. The theory behind using them is that conventional bolts/ torque methods are inaccurate due to friction at max load as Chaz stated. By using torque to yield bolts the torque is way less than max tensile strength so cuts down on friction. Then during the degree rotational the bolt enters into its plastic state (stretching point) resulting in an even and accurate torque.
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11-06-2017, 08:41 PM #365000 RPM
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Thanks again..
Service Manual "Powerhead" page 4-55:
“When connecting rods are attached, and bolts
drawn down finger tight, torque rod-cap bolts to
15 lb. in. (1.7 N·m). Recheck alignment. Retorque
5/16 in. bolts to 30 lb. ft. (40.7 N_m). Recheck
alignment. Turn each rod-cap bolt 90 degreesfurther
after 30 lb.ft. reading is acquired.”
So, based on what you all have said, this is the procedure I should follow? Can I say in my day I have snapped a few bolts, not from carelessness but from what I thought was the correct "torque" I know what it "feels" like just before the dreaded snap and that is what the bolt felt like at 30lbs and 90 degrees more. So, am I good to go here? Would the majority here do the same, follow the service manual?
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11-06-2017, 08:55 PM #37
Only if you are using new oem bolts. They will feel like they are stretching, because they are by design. If you reuse any I wouldn't do the 90 because they have already been stretched ( really need new bolts). The SPS or ARP bolts will not be torque to yield bolts and will be just torqued with no additional turns. Lots of guys just torque to straight 30 with the torque to yield bolts with no additional rotation with no problems, but technically the 90 is needed with new torque to yield bolts for the designed clamping force of the bolt to be reached.
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11-06-2017, 09:52 PM #38Screaming And Flying!
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Re use at 45% with red...pre stretched..Just in case look at your tk wrench as ya turn the bolt. Put rod in vise and turn till threshold. The bolt the streaches. I call em rubber bolts. At %90 ya reading 50 lbs. after that it goes rubber.
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11-06-2017, 10:07 PM #39
Last edited by W2F a V-King; 11-06-2017 at 10:21 PM.
James H. W2F a V-King... Want 2 Fly a V-King
Dedicated Site for Hydrostreams >> http://hydrostreamforums.com/
My Project 1979 V-King restore >> http://hydrostreamforums.com/viewtopic.php?f=9&t=2761
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11-06-2017, 10:31 PM #40
Still a little different than a torque to yield bolt. That's torquing a conventional bolt by using stretch to achieve its maximum clamping force. A torque to yield bolt will only tighten to a preset value by design then goes into what they call a plastic phase, which is simply begins stretching. They will stretch up to a predetermined length before they break which is much greater a distance than a conventional bolt can stretch. Their most clamping force is achieved in the plastic phase. A conventional bolt's most clamping force is achieved near its yield level just as it begins to stretch any more and it breaks.
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11-07-2017, 12:18 AM #41Screaming And Flying!
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I always wondered why merc dont trust the rod bolts so loctite them and omc says just use tcw
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11-07-2017, 06:31 AM #42Screaming And Flying!
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Omc Merc....2 diff beasts. omc has diff bolt thread cmbo. Also mating surfaces on rod. Gotta think .....what and how much ... rod bolt. Most motors blow..... stuck piston...crazy rod.... not bolts.
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11-07-2017, 06:46 AM #43
New OEM bolts are cheep and use the OEM toque procedure.
Lots of talk about how not to do it. It is a stock eng no need to get crazy.
.
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11-07-2017, 08:11 AM #44
I am surprised no one eagle eyed this . You mentioned it twice , and I mentioned it once in random thought's ....
If you really did pull one " A HUNNERT EIGHTTY " degree's past 30 ft/lbs , you might want to look at the overall condition of that rod ..!
Anyone else who thinks that's normal ... I gotz a 3/4" air impact they can borrow fer modder buildin ..
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11-07-2017, 08:15 AM #45Screaming And Flying!
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