Engine Alignment

[Frank Langer]

Hi,
The books recommend annual engine alignment, but very few owners actually do that. I can tell when it's due by a slight increase in vibration, a little more difficulty spinning the prop by hand.
So yesterday I assembled the required tools and got to work. I almost had it, with no gap in the coupler on three sides and just a slight gap on the top fourth side, and the shaft spun quite easily. But I decided to raise the front engine mount bolt slightly to close that fourth gap, but that slight change screwed up the others so I was back to square one. I tried to reverse that last change, but it still wasn't right. I worked at it some more and got very close to good, and called it done. Today I took the boat out to check it all and sail some. It immediately became apparent that I still had more vibration than I want.
So back to the dock, tools out, and more work. I tried to be very methodical, making small incremental adjustments, both vertically and horizontally, and after an hour and a half got to no gap on three sides and a very slight two one thousands gap on the last side, with the prop shaft spinning with one finger pressure. I was pleased with that, put it all together again, and crossed it off on my To Do list.
In summary, I think engine alignment is important, though time consuming and frustrating. Sometimes it's best to know when to stop trying for perfection. If it's really not right, try again. The satisfaction of success at this nasty job is worth persevering, and then celebrating with your favourite drink.
Just my thoughts for those who haven't thought about their engine alignment.
Frank

 

[Pete the Cat]

Engine alignment can be very frustrating, but once it is done it is generally good for a long time and worth the effort in my experience. I have owned other boats, but I think the TAFG is so rigid that the Ericsons with that construction will hold alignment better than many others boats that change form slightly when hauled. The key to making it work is to do just as you did: be very patient, methodical, and make very small (one eighth turns each time) movements each time. Make sure you move top nuts and lower nuts in unison, plan each move and measure gap at every movement--if you simply loosen the top nuts, align it and then turn things down--it can screw things up. This is something that is a PIA to do, that I have seen yards screw up repeatedly for whatever reason--they have a a hard time charging for the time involved, and is something owners with a modest mechanical ability, a gap gauge and adequate patience will likely do as good or better job than the yard. Will greatly reduce vibration, wear, and noise.

 

[bigd14]

I'll admit to not doing this, although I do check regularly to make sure the prop shaft turns easily by hand (it does). It's on my list for fall or winter. Are there any considerations for doing this with a PSS installed? Does that make it easier to measure the gaps since there is pressure against the coupler? I also have 4 point mount, which I understand will make this task more difficult. I'll prepare myself for hours of frustration, get an early start and give myself the entire day to complete it.

 

[Frank Langer]

I'll admit to not doing this, although I do check regularly to make sure the prop shaft turns easily by hand (it does). It's on my list for fall or winter. Are there any considerations for doing this with a PSS installed? Does that make it easier to measure the gaps since there is pressure against the coupler? I also have 4 point mount, which I understand will make this task more difficult. I'll prepare myself for hours of frustration, get an early start and give myself the entire day to complete it.

Hi Doug,
Although I check and usually redo the engine alignment on my boat every two years, sometimes a bit more often, my guide as to whether it needs it is if I can turn my prop shaft both under water and inside the boat at the coupler by hand easily with no apparent friction, and secondly, if I get vibration in the cockpit--a slight shuddering noise, lifelines vibrating, etc. If you have no symptoms and your prop shaft turns easily, I would be inclined to accept that as good enough, though diligence might suggest you still do it, despite the aggravation. Don Casey suggests that if you can turn the prop shaft, it's good enough, but I think that's a bit too simplistic, as most will turn, but it should do so fairly easily. You could start by removing the bolts holding the two coupler sides together, pulling back on the prop coupler and then letting it slide together again, measuring with feeler gauge on the four quadrants, and if they are within .002, call it done and reassemble the coupler bolts.

In answer to your question, the PSS makes it a bit more difficult in my opinion as the prop shaft is under some pressure from the rubber bellows, making it a bit harder to pull the prop side of the coupler away from the tranny coupler after you have undone the bolts. The coupler needs to be pulled back each time you make an adjustment, and then allowed to rest up against the tranny coupler to see how it fits. They need to slide together without any hitch, with the two coupler sides being totally flush (ie. no overlap side to side or top to bottom), and then using a feeler gauge on all four quadrants with no more than a .002 gap, and even that is probably the maximum to avoid vibration.

This job would be much easier if you had a helper, as then you could remain in the cockpit locker doing the measurement, and your helper could be in front of the engine adjusting the motor mounts and levering the engine as required. A helper would avoid you having to climb in and out of the locker each time you have to make an adjustment--could be 25 times or more before you get it just right, in my experience. Prepare to be sore the next day! Good luck!

Frank

 

[Kenneth K]

My boat had one of these installed when I bought it.



Mfg says shaft alignment to .01" is sufficient when using one. One problem though is it extends the prop out further from the strut by about 1.5". The boatyard removed my flex coupling when I had them install a new PSS and shorten my prop shaft.

I didn't notice a change in vibrations before or after.

 

[bigd14]

A helper would avoid you having to climb in and out of the locker each time you have to make an adjustment--could be 25 times or more before you get it just right, in my experience. Prepare to be sore the next day!

Thanks for the detailed explanation Frank that’s helpful. Luckily I modified my quarterberth to allow access to everything. I can slither all the way from the quarterberth to the cockpit and vice versa and there is no water heater in the way just the spare battery in its box. I could remove that for even better access. This will save my bacon! The port rear mount will be challenging nonetheless. I’ll bring a bottle of ibuprofen anyway.

I can turn the prop very easily using one finger on the coupler. I would say it’s really quite smooth. So by Casey’s estimation that would be good enough. But I do have some vibrations. So perhaps there is more to to be gained. At the very least I’ll unbolt the coupler and see what the measurements are. Thanks again.