Mercruiser Alpha one coupler runout still a problem after new replacement.

tlrourke2

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Mercruiser Alpha One Triangle Engine Coupler Runout

Having problems with coupler. Found out that the BOAT standing for "Bust Out Another Thousand" was true. Having problems with alignment. Removed engine re-check flywheel run out being found to be (.003"). Had to align the coupler once re-installed and got it to (.003) parallel and when found the angular to be (.002"). When checking the internal counter bore at the beginning of the splines I found it to be @ (.027"). I don't see any visual signs of damages what so ever. Question is "Shouldn't the outside housing that contains the rubber and spline section run true with the splines themselves?" I went ahead and installed engine and turning the crank turns any thing close to an alignment into *&%% ! Another issue was that I didn't know how to even out the load on the front mounts??? This is my first time around in the stern drive world...... PLEASE HELP ME !!!!
 

tlrourke2

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Mercruiser Alpha One Triangle Engine Coupler Runout

Always ran inboard the packing , strut , Etc. Put a ton of money into all else and down to plugging in the stern drive. Curious about engine to driver / driven alignment researched and purchased all the needed tools and parts except for new coupler. Old coupler seems to be in good condition , that is , no visual abnormalities and very little internal wear in the splines. Unaware of the alignment of coupler to flywheel procedure on installation of engine had to pull back out to align and check runout. I did try to align with tool but found via indicator that the triangle couple housing that contains the spline section suspended in rubber had (.020") runout so alignment was good until the crank was turned then way out of tolerance. Here we go.... Removed engine , set solid , removed bell housing and triangle coupler , found only (.003") runout for the flywheel , re-installed coupler with snug bolts , used indicator on the housing of coupler and tapped around until only runout observe
 

alldodge

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Always ran inboard the packing , strut , Etc. Put a ton of money into all else and down to plugging in the stern drive. Curious about engine to driver / driven alignment researched and purchased all the needed tools and parts except for new coupler. Old coupler seems to be in good condition , that is , no visual abnormalities and very little internal wear in the splines. Unaware of the alignment of coupler to flywheel procedure on installation of engine had to pull back out to align and check runout. I did try to align with tool but found via indicator that the triangle couple housing that contains the spline section suspended in rubber had (.020") runout so alignment was good until the crank was turned then way out of tolerance. Here we go.... Removed engine , set solid , removed bell housing and triangle coupler , found only (.003") runout for the flywheel , re-installed coupler with snug bolts , used indicator on the housing of coupler and tapped around until only runout observe

:welcome: to iboats

According to latest service manual bulletin flywheel run out shall not exceed .008 inch. Y should use taper screws to center the coupler per bulletin. If all together and coupler is still to far out the coupler is suspect.

http://www.marinemechanic.com/merc/...d/New Folder/coupler-install-change_EN_11.pdf
 

tlrourke2

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Thanks for the reply. I pulled engine to check. Removed coupler and checked flywheel at outer face edge TIR was (.003"). Re-installed coupler and had to use indicator to true up. I squared the coupler up to flywheel by indicating off of the part of the coupler used to house the rubber and spline insert. I assumed that the unit was built for the housing and the spline to run true together. Indicating on the external housing of the coupler I got it within a couple of thousanths but when I checked runout of the smooth internal section of the counterbore right before the splines started I found a total of (.027") runout. Rechecked the outside (Part of the coupler that houses the rubber and spline insert) and it was running true (within a couple of thousanths) as it was right before I checked the internal bore. I don't see any signs of damages on the coupler , it just seems as though each component of the coupler should run true together..... I could be wrong.....its happened before. If I were to adjust coupler to flywheel taking out the runout then the housing part would have runout and may cause vibration.... I just don't have enough experience at the Mercruiser stuff. Im thinking of replacing the coupler but I wish I knew for sure......
 

alldodge

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If the engine was out of alignment and sat for a long period without running the rubber coupler would be in a bind. The coupler will the be off center and may stay that way. Some have installed the drive and used for a short time, then recheck alignment. I can come out of it but there is a possibility of causing more problems depending on the amount of bind. After doing all this work to the engine I would lean toward getting another coupler. If the engine is easy to pull you could try and see how it changes over a short period of time. Just my opinion others may suggest something else.
 

tlrourke2

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Makes sense. Seems like I bought the boat from a fella that only knew or only cared about gas fill up and run it in the ground. I was led to believe just an engine... I stopped engine build midstream to get the compartment ready and that was when I found the rotten stringer and a coupler of other major areas of concern. Seems as though instead of replacing (1 1/4") transom drain sealing w/ 5200 and flaring to secure he chose to use a piece of (1") PVC with clear silicone around the ends then an unsealed Garboard. I walked right into this but after all this work its almost finished now....
 

alldodge

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It sounded like your someone which wants to do it right, :thumb: and she almost ready for the water.

In the process my self of rebuilding a transom :facepalm: but it will be ready come spring. :D

Have a good one
 

NHGuy

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I'd think you could get a good read on coupler spline runout by putting your alignment bar in and measuring off of it.
The coupler could have been tweaked by having the shaft in it while the engine sagged on the bad stringer.
 
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tlrourke2

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I am at my ends. I have put forth non stop effort and tons of cash into this boat. I had a problem with coupler runout with a used coupler. I bought the boat and found bad stringer and the guy didn't seem to have any sort of mechanical knowhow at all. I bought a brand new coupler because the old one had so much runout. I checked my new flywheel and Im @ .003" on the face or "Angular and only .0015" on the rim or "Parallel" on the runouts. Adjusted thrust prior to every reading then I return to a marked reference point marked with paint marker to make sure the indicator in coming back to zero. I put the brand new coupler on andwent from "0" to -.040" then before the round was over I went to a +.010" ten back to "0". After thinking about it for a while I figured maybe the boltholes on the flywheel may be offset so I drilled them over by 1/32" now I see that I was trying to take out for parallel when I have a good bit of runout at the end where it holds the grease indicating a problem with an angular issue. I don't think it should be like this ????? I work offshore and I work on engines including setting up new equipment in which involves aligmments..... Should it be this complicated to install a freakin Mercruiser part???????
 

tlrourke2

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I am at my ends. I have put forth non stop effort and tons of cash into this boat. I had a problem with coupler runout with a used coupler. I bought the boat and found bad stringer and the guy didn't seem to have any sort of mechanical knowhow at all. I bought a brand new coupler because the old one had so much runout. I checked my new flywheel and Im @ .003" on the face or "Angular and only .0015" on the rim or "Parallel" on the runouts. Adjusted thrust prior to every reading then I return to a marked reference point marked with paint marker to make sure the indicator in coming back to zero. I put the brand new coupler on andwent from "0" to -.040" then before the round was over I went to a +.010" ten back to "0". After thinking about it for a while I figured maybe the boltholes on the flywheel may be offset so I drilled them over by 1/32" now I see that I was trying to take out for parallel when I have a good bit of runout at the end where it holds the grease indicating a problem with an angular issue. I don't think it should be like this ????? I work offshore and I work on engines including setting up new equipment in which involves aligmments..... Should it be this complicated to install a freakin Mercruiser part??????? I purchased a new Sierra coupler from Ebay. I wish I had a lathe where I could chuck it and true it up. I could complete checks on this thing to see if its defective and then may face off the surface that mates with the flywheel..... God I just wanted a boat.... something after all those years of child support now Im stuck on this issue. Am I wrong? Should you have to shim these things to correct for offsets???
 

NHGuy

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Does the coupler mating surface have paint on it? Try it all 3 ways, it bolts up 3 ways right?
Don't be as concerned with the exterior of the raised center. It's the splines that you want to spin true. Stick an alignment bar in there and see how it turns.
I will look through my manual and see if they give a runout specification.
Do you have the 3 rubber feet that sit between the coupler and the flywheel?

To check runout Mercruiser says to torque the flywheel to 75 ft/lb and push it in, then put a dial indicator on the back just inside the ring gear. You want under .008" of runout. So that .004" is OK.
The coupler gets 35 ft pounds. But has no runout spec that I see. Maybe since it's rubber it's less precise. If you want the best quality maybe you should go OE.
Sierra is the aftermarket for boats.
 
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tlrourke2

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I just checked it agin and trued up the tube side connected to the spline insert.
 

tlrourke2

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Sorry didn't get to complete..... I had a TIR on the tube end @ (.004") but when I measured the housing I was @ (.051" TIR). I don't know for sure but I would assume that much would cause an imbalance and a problem. I would really like to assume that the housing or body that mounts the unit to the flywheel has to run true with the splines.... Wouldn't you say that would be accurate to assume that. I had the same problem with the one that came with the boat so I bought a new one !!!! God , I just want to get this thing finished....
 

tlrourke2

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I was going to make sure all was well after I replaced the coupler then get in boat and hang front , get the final alignment complete then finish all the other loose ends but I cant seem to get past this....
 

alldodge

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The outer housing is expected to be true but not always, there are several times folks have found the outer housing to be out. There are even some Utube videos showing the outer housing to wobble. The face spline runout should be measured and not the housing. Correct me if I'm wrong but, in a previous post didn't this initially start with being unable to align the engine using the alignment bar? This then started the checking of runout.
 

tlrourke2

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Sorry for the delay I was trying to see if I could find a medium for the issue at hand.... Yes that's correct I had a coupling that came on the boat. All has been rebuilt not just the engine. The guy didn't seem to be able to maintain a boat hence the engine , sterndrive , stringers , any wood substrate in engine compartment along with the glass , Etc , Etc.... For some reason I have a new replacement and I have the same problem. I bought one in a package deal with some hydraulic parts. The unit was new in box with paperwork. I just noticed this site has the OEM... that's what I should have purchased. I checked all that could be checked on the engine and in good order. Brand new crank & flywheel in engine. When I first started the housing runout was around (.060" TIR) and the tube that holds the grease zert was out approx. (.042" TIR)..... IN THE OPPOSITE DIRECTION.... It just seems if I true up and leave the mass of the housing rolling around like that it will cause vibrations / noise / other failures.....
 

tlrourke2

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If this don't work out I wonder how long it would take for this outfit to get the OEM.... I split up the TIR with priority being the spline socket where I have (.011" TIR). I cant find the OEM tolerances. Does any other vendor or anyone know the Mercruiser engine coupler tolerances for alignment??? I sure do appreciate the final word on the mystery between housing and spline geometry not matching up sometimes , thank you very much !.
 

achris

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Hey man, just slow down a bit. I know you're frustrated, but shouting never fixed anything. Let's start with what you're working on. Engine model and year would help, serial numbers would be better. The more information you provide, the more people who'll be willing to help. (We don't need to know anything about the boat either, this is an engine problem, nothing to do with the boat)...

Just so you know, I work offshore too... ROV pilot. And I may be in GoM in a few months (keep an eye out for me :))

You also seem to have 2 threads running on this subject, so I'll merge them.
 
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alldodge

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If this don't work out I wonder how long it would take for this outfit to get the OEM.... I split up the TIR with priority being the spline socket where I have (.011" TIR). I cant find the OEM tolerances. Does any other vendor or anyone know the Mercruiser engine coupler tolerances for alignment??? I sure do appreciate the final word on the mystery between housing and spline geometry not matching up sometimes , thank you very much !.

Have never seen coupler tolerances on a new or used coupler. As before many have found the outer housing of the coupler to be out of round while the spline is not. Don't know for sure but you might just be over thinking it. Sure we all want everything to be true but we have to work with what we have. Not saying that your new coupler is defective but is there a possibility your over thinking it. It may be a pain but what about installing the engine and check alignment
 
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