Engine coupler help!

[Stugy]

Hi, I was wondering if anyone has any experience with their engine coupler? I need to align my engine and I think the coupler is bent.
I took all 4 screws out on the coupler and both sides now don't align perfectly straight as it should. It seems the coupler on the prop-shaft is the problem it has 2 screws that seem to be holding the shaft in place I am afraid if I remove the screws the shaft will let go and go to the bottom of my marina or would the shaft be still be held in place by the cutlass bearing?
Please help!
the symptom is when I run my engine in gear the engine just ratles a lot, and has excessive vibration.

Thanks !

 

[NateHanson]

You may only need to align your engine. You can start to trace the problem by using feeler gauges between the two flanges. Slide them together and see which side has a gap, then turn the prop shaft and see if the gap stays in the same place. If it does, then your shaft coupling is fine, but your engine needs aligned. Move the front of the engine toward the gap (ie, gap on the bottom, lower the front of the engine). However, if the gap moves with the shaft flange (ie, gap on the bottom, turn the shaft 180 degrees, and now gap on top), then your shaft coupling may not be perpendicular to the shaft, and you might need to take it to a machine shop.

If you want to take that coupling off the shaft, put a metal hose clamp around the shaft, forward of the stuffing box. That will keep the shaft from sliding into the briney deep.

 

[Stugy]

I checked both flanges and the one on the shaft side is wobbly, it will not line up perfectly to the one on the engine side and when It rotates it will wobble a bit, now the boat is in the water if I take the flange out of the prop-shaft can I just take that to the machine shop? or do i need to take the flange and the shaft?

 

[missalot]

From my experience, shafts and couplers are "trued up" as a unit. So, to get much benefit from taking the coupler to a machinist, you would need to take the shaft with it.

On vibrations, check your motor mounts to be sure they are secure. The last "alignment" vibration I had turned out to be a loose motor mount.

good luck

 

[rwthomas1]

It is conceivable that the coupler is warped/bent and the shaft is fine. If you are concerned about the shaft sliding back out of the boat when you remove the coupler then simply install a spare shaft zinc on the shaft inside the boat to keep the shaft from going anywhere. Mark the shaft and coupler with index marks so you know how they are "clocked" when you reassemble. Removing the coupler and turning the shaft may reveal the shaft is bent. Check the coupler closely and if all is well reassemble, then you may have to realign the engine to correct your problem. RT

 

[tenders]

My sympathies, I find these kinds of things very frustrating to diagnose and unpleasant to repair. Engine alignment is an acrobatic exercise but possible to accomplish when you know that the engine is the only variable. But when you're unsure about the trueness of the engine, shaft, and coupling all at the same time you may never know whether what you're doing is helping or hurting.

So you basically have to assume everything except one this is pretty close to perfect, and fix that one thing to the best of your ability.

It seems most unlikely to me that the coupling itself is bent, ie, that there is a distortion between the face that bolts up against the engine and the casting allowing the shaft to stick out at 90 degrees from the face. There is too much flex in the shaft and engine mounts to make this happen under any circumstance I can imagine, and we're talking what, a 3/4" shaft with two or three feet of run, right?

Unless you or a previous owner have been involved in some unusual maneuvering/navigation your E27's shaft is pretty well-protected by the keel and the rudder. However, the shaft could be bent if the boat was left sagging on the hard from an improper jackstanding. The best indication of this would be the integrity of the rubber cutless bearing and the amount of play of the shaft within it. How is that? A tough question to ask with the boat in the water, I know.

Engine alignment is far and away the most likely problem. The mounts get soft, the boat settles a little, the fore- and backstays have been pulling the boat out of its original shape for decades, etc. Unless you have a reason to suspect otherwise, before I assumed shaft or coupling problems I would probably pursue alignment up through replacing the mounts using a bottle jack to raise the engine.

 

[Guy Stevens]

Couplers can get bent.

The coupler can get bent, generally this occurs when people are removing them from the shaft using the old socket and bolts trick. They tighten the bolts up in a rotation or only use two or really have to torque on them, and they get bent.

Couplers can be trued up by a good prop shop or machine shop that knows what they are doing seperate of the prop shaft.

Shafts do get bent, and are impossible to check while in the boat. They are checked with a very flat table, and height gauges. .004 is about the most that you ever want a shaft to be out. I have seen then so bent that you could see it with the naked eye rolling along the parking lot.

Guy

 

[Stugy]

Well I worked on this all day, and I think I got it fixed, I replaced the 2 front engine mounts and aligned the engine to the best of my ability. It had the same gap all around the flanges.
now it seems to run pretty smoothly for the most but i find it strange that at 1,600 RPMs it ratles but if I stay below 1,600 or go above 1,800 it runs very smooth.
I want to thank u all for your sugestions..! it made the troubleshooting a lot easier.

 

[NateHanson]

but i find it strange that at 1,600 RPMs it ratles but if I stay below 1,600 or go above 1,800 it runs very smooth.

Sounds like a sympathetic vibration. Something might be loose, and rattles just when the engine hits the rpm that allows that loose piece to waggle at it's most natural speed.

 

[Emerald]

And you may get that vibration at 1600 RPM even if there isn't anything loose. If you hit the right harmonic frequency, the vibration of the engine may match the resonance of something else (I've watched back stays do this), and that something else will just start vibrating and singing away. Change the RPM, change the resonance/frequency of the beat, and it all goes away. So, do make sure things are nice and snug (don't over tighten - that stresses parts), but if all seems OK, just keep an eye or ear on it for any change, and enjoy - if you get a change or it gets worst, dig deeper - if it stays constant and predictable, you probably are OK.


-David
Independence 31
Emerald

 

[Shadowfax]

Next time you are in the water, duve under and see if you can move the shaft or prop around. You may have worn out the cutlass bearing

 

[tenders]

You could also have a loose shaft zinc.