Coupler Alignment - Vibration

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SolomonsDrake
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Posts: 13
Joined: Mon Jun 14, 2021 10:36 pm

Coupler Alignment - Vibration

Post by SolomonsDrake »

My mechanic installed two running takeouts (318s with 1:1 transmissions) to replace the same engines/transmissions. He is having a ton of trouble getting the Port engine alignment right and there is significant vibration over 1600 rpms. He has tried adjusting the engine angle ad nauseam. The isolation spacer between the transmission and shaft couplers appears to be straight. The couplers also appear to be straight and aligned, but then when he tightens down on the bolts connecting the couplers it creates an uneven space that we believe could be causing the significant wobble/vibration. The shafts were not changed out with the engine swap and didn't have problems before. The cutlass bearings were replaced in April.

Anyone have this issue before? Any thoughts on next steps/things to try? Any other things to check that could be causing this?

Thanks!

Tim
Voyager
1977 32' Sedan Flybridge
Twin Chrysler 318s
Chesapeake Bay
TinLizzy
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Location: Lake Superior-Michigan's U.P.

Re: Coupler Alignment - Vibration

Post by TinLizzy »

Is he using a feeler gauge to get the engines in alignment. Ideally it will be .003" or less out of true. That is as close as i got on my old 28 ft. when I installed new shafts, i could have got it a little better, but the run out on the transmission coupler was .003".
Rodney
1975 28 Express-Twin 350 Chevy's, SOLD
1990 32 Express--Twin Chevy
Portage Canal Waterway-Upper Peninsula,Lake Superior
Fastjeff
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Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: Coupler Alignment - Vibration

Post by Fastjeff »

If the coupler flange/ flanges run out it's impossible to align the coupling. So how can you determine if this is the problem? It's not easy, but it can be done.

For the trans side: Mount a dial indicator on trans and spin the coupling over. It should be okay since it's precision machined, but it COULD be bent.

If it's okay then the prop side flange is running out (which is most likely). That means it needs to be machined (see below), but if you want to make sure here's what to do:

Push the prop shaft backwards until it bottoms on the stuffing box. It has to slide smoothly as it rotates or the shaft will wiggle fore and aft to mess up the dial indicator readings. Dial indicate the flange surface as a helper slowly turns the prop, and if the runs out is more than a few thousandths of an inch it has to be fixed.

Pull the coupling and shaft, mount the coupling back on the prop shaft, and have a machine shop turn the face of the flange until it's true.

Since the lathe operation will most likely be needed, I would pull the works out and send it to the machine shop. Had to do that on mine.

Good luck!

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington
SolomonsDrake
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Posts: 13
Joined: Mon Jun 14, 2021 10:36 pm

Re: Coupler Alignment - Vibration

Post by SolomonsDrake »

Thanks, Jeff! Much appreciated. Will come back with updates. Currently in the water, so might not get to pulling the shaft for a little while. How risky is it to run it at lower RPM in the meantime? What am I risking in terms of transmission damage/wear?

Tim
Voyager
1977 32' Sedan Flybridge
Twin Chrysler 318s
Chesapeake Bay
Fastjeff
Site Admin
Posts: 1473
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: Coupler Alignment - Vibration

Post by Fastjeff »

If you run it so slow that you're not getting vibration it might be okay.

Personally, I would run that motor only to get in and out of the slip. My old 32 footer worked fine on one motor.

Jeff

PS: It would be hard to rotate the prop for dial indicating with the boat in the water!
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington
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