Just how critical is engine coupler alignment?

[Cool Beans]

Not sure what the best forum for this would be. . .

So anyways, I dropped the block less accessories into the boat last week. I let it settle over night and aligned it. Pain in the ass it was, but I got it to .002". I bolted everything back up to it less the exhaust and checked the alignment again. . .it was off by .005" So I realigned it, got it to .003". After installing the exhaust, I checked and it was less than .002"

Sweet! Bolted it up and called it good.

So I was running the engine for the first time yesterday, and it was squealing when put in gear. Squeal didn't go away when I tightened the belts, so I detached the shaft coupler to check for true. . .it was less than .002", so still good. I then ran the engine without the prop shaft and no squeal. I checked the alignment once more when I hooked the shaft back up and it was off by .005"!!

***? If the alignment can be throw off just by touching the motor, just how critical is it? Am I missing something? I am an anal-retentive perfectionist, maybe that's the issue

[Dave Neptune]

What size haft and how long? The changes could be from the engine settling. The squeal should be identified, IE packing or strut? Could be just a tight packing.

Dave Neptune

[Cool Beans]

1" shaft. . .40" long I think. . .

How long does the engine take to settle?

As for the squeal, I found a new square key in a plastic baggy when I was cleaning up I can't remember if I put the old key back in the new drive coupler or not. . .oh, the adventure continues, lol.

[hanleyclifford]

Is the boat in the water?

[BadaBing]

I won't pretend to speak with any authority on this but will ask a question that may hall answer the original question as to how perfectly aligned the shaft engine must be.
If an engine is mounted on vibration absorption mounts, which are basically a steel ball in a hard rubber socket, how much movement will be allowed in the engine by the mounts. I would guess much more than .005".
I would also hazard to guess that an average shaft could be forced to shift off center by .005" inn the coupling when a single set screw in tightened.

I assume the transmission is in gear and the shaft is spinning ? Could the squeal be a better out shaft packing? Careful you might be eating up the shaft in the packing?

[JOHN COOKSON]

Put a finger on the packing gland while the shaft is turning (or use an IR thermometer) to see if the packing is running hot. Also what is the drip rate through the packing gland?
I presume the boat is in the water?

TRUE GRIT

[Cool Beans]

yes, boat is in the water.

I'm going to run it tonight after work, check the packing gland for hotness. . .maybe back the nut off a bit, increase the drip rate. it drips, just not much. it's been sitting since January

Thanks!

[Al Schober]

Just a thought - if the alignment is going out horizontal, the engine may be shifting on the studs. The holes in the oil pan are a lot bigger than the studs and will allow the engine to shift sideways unless you put something in the gap (Bondo?) when the alignment is good.

[BadaBing]

Prior to my partial overhaul this past winter, I discovered this while pulling the engine apart, all of my mount studs had stripped or work the threads out in the wood engine mount rails. Essentially my engine was pretty much held in place by gravity. I bet my alignment was a little out of kilter.

[hanleyclifford]

yes, boat is in the water.

I'm going to run it tonight after work, check the packing gland for hotness. . .maybe back the nut off a bit, increase the drip rate. it drips, just not much. it's been sitting since January

Thanks!

1 drop every four seconds is a good standard to shoot for.

[JOHN COOKSON]

CB:
I found when I get down to the fine adjustment on the packing nut it helps to mark the packing nut with a drop of paint or finger nail polish before turning it so you can keep track of how much you have turned it.

TRUE GRIT

[67c&ccorv]

Best place to do a shaft alignment is with the boat in the water.

[Cool Beans]

Don't you love it when problems disappear on their own? So I didn't get a chance to run it until today. Dropped it in gear and ran it WOT while tied in the slip. . .30 minutes or so, helping to seat the rings, checking for leaks, etc.

No squeal noticeable. Drip was about 1 per second. Stuffing box was warm to the touch, but not hot. Never got anything more than warm.

Going to mess with the alignment again tomorrow. It's better than it has ever been since I've owned it. That being said, the values change ever so slightly as you rotate and seat the coupler in different positions.

I've had the shaft and coupler checked for true last haul out (they are new).

I wonder if the out of round, coupler true, and new drive flange true are in spec but at the max values, just how far off could you be when trying to align?

[hanleyclifford]

.003" is acceptable. If both halves are slightly out of true there will be a "sweet spot" where the two will mate for the least tolerance. Bolt up at that setting and mark both with a punch.