Home › Forum › Ask A Member › Shaking at High RPM Running 1955 Evinrude Fleetwin Aquasonic 7.5HP
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fleetwin.
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October 11, 2019 at 2:38 pm #185050
As Fleetwin said, these are both damaged from the shock absorber being expanded. Neither of them appears unusable if cleaned up. The shock absorber from either of these would need to be compressed back to at least close to original size. If you do not weld the seam, it may work for a while, it may for forever if you don’t hit anything with the prop, or it might fail on you 5 minutes into the first run.
I know you said your broke the shock absorber from your original gearcase. While I’m not quite sure how that happened, you have another one now. My suggestion for getting this one back to a usable length is as follows. It may sound like hack work to some, but it will work and I can’t imagine breaking on using this method.
Take a length measurement of the shock absorber first. Open the jaws of a bench vise to allow the stub shaft that drives the pinion gear to slip through but still firmly support that half of the shock absorber. Sit the shock absorber on top of the vise jaws with the stub shaft hanging between the jaws. Using a brass hammer (maybe 2lbs) give the top half a couple good whacks straight down to drive the top half into the bottom half. Take another measurement to see what progress was made by the first try. A few strikes with the hammer is usually enough to get the halves back together. If the piece now measures the correct length stop. If it is still too long try again. If it doesn’t go all the way back to the correct length as it is not wearing against the bottom of the bearing carrier for the drive shaft, that is enough. It just may not work in another motor if it was swapped out later. If you are able to weld it, it can be welded now. That will prevent it from expanding / breaking later. If you are not able to weld it, you can try using it as-is and it may or may not work without issue from that point on. When you got the last one back to 6.75″ I’m sure that was good enough. If it was over 7″ you squeezed over 1/4″ out of it which nearly 100% of that should have been clearance if it came out of your gearcase at the 7″+ dimension.
If you do not have functional vise anymore, a hole large enough for the stub shaft to pass thru in a steel plate will also work. You just need to support the lower half of the shock absorber while you force the top half back into it. You do not want to apply force to the stub shaft that drives the pinion. That part is only designed to take rotational force. Not axial or side loading. It is pinned in place and that kind of force will damage it. I hope this helps.
-Ben
OldJohnnyRude on YouTube
October 11, 2019 at 4:41 pm #185065OK, so the one on the left is currently being used on the 54 gearcase that is on the engine now, correct? Unfortunately, that one looks like it has been rubbing on the driveshaft also, hope it works out OK…
October 11, 2019 at 6:47 pm #185084The newer prop incorporates a “fishline cutter” which must be trimmed when used on the earlier motors. That violent bucking sounds more like a worn clutch dog. Check for a bent 303340 shift lever in the lower unit.
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This reply was modified 5 years, 4 months ago by
garry-in-michigan.
October 11, 2019 at 6:50 pm #185086The newer prop incorporates a “fishline cutter” which must be trimmed when used on the earlier motors. That violent bucking sounds more like a worn clutch dog. Check for a bent 303340 shift lever in the lower unit.
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This reply was modified 5 years, 4 months ago by
garry-in-michigan.
October 13, 2019 at 2:18 pm #185193So it damaged the driveshaft placing it in the vice and squeezing it back together? I saw this on another thread.
October 13, 2019 at 2:21 pm #185194I broke the other drive shaft using a hydraulic car jack against a steel I beam.
October 13, 2019 at 7:57 pm #185244Inside the 55 lower unit.Shift Rod was bent.The Lower driveshaft from the 54′ was extended to 7″ got it back to a bit less than 6 3/4. Reassembled everything in 55′ lower unit. Motor is Complete.
October 14, 2019 at 2:47 pm #185318Great to hear it is back together and complete. Hopefully that shock absorber stays together after getting it back to less than 6.75″ and doesn’t fail on you. Sometimes they give trouble free service for a long time after doing that.
-BenOldJohnnyRude on YouTube
August 14, 2020 at 1:48 pm #211632I would like to update this old thread here. I finally found the source of the noise problem inside the powerhead. One of the screws that are connected to the piston came loose and hit the crank.Probably also the source of the shaking!.So I Got a new powerhead. Now its on to only pumping water at 1/2 throttle.Other than that its running great.
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This reply was modified 4 years, 6 months ago by
Mumbles.
August 15, 2020 at 8:05 am #211680Boy o boy, thought only I had this kind of luck….I’m surprised it didn’t throw a rod…I’ll bet it vibrated quite violently…
OK, so now you have a replacement powerhead but it doesn’t pump water correctly?
Seems like the powerhead has to come off again….Did it pump correctly with the old powerhead? Did you have the gearcase off again when you installed the replacement powerhead?
If the engine pumped water fine with the old powerhead, and you didn’t pull the gearcase off when you replaced the powerhead, perhaps there is an obstruction in the new powerhead…Did you do a compression test on the replacement powerhead, maybe the head gasket is blown.
If you pulled the gearcase when you replaced the powerhead, perhaps you misaligned the water tube/grommet. -
This reply was modified 5 years, 4 months ago by
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