Proper shim material for engine alignment?

[JPS27]

Long story short is that my trans and shaft couplings were found to be out of alignment on my recent 2yr-haul out. I have an ericson 27 and a Yanmar 2qm15. Neither I nor people I know who know what they're looking at can figure out why the engine was out of alignment from the last time it was checked (2 yrs ago, new prop install). But the engine coupler is low to the shaft coupler by about 3/16". One thing that is clear is that the mounts need replacing and that they were adjusted to their max height.

The engine was shimmed before using starboard or something that looks like starboard. It seems intact and solid.

My question is, should I use something different than these same shims? I have seen on-line where starboard is mentioned as shim material. But the references of the best material appear to be GPO3 or G10, aluminum. I've also been told that I could go with fir or oak wrapped in glass or epoxy coated.

I would really appreciate some thoughts before I delve into the next stage toward getting back in the water. Thanks

[Terra Nova]

Don't use Starboard, as it could cold flow. Use a stable material like G10.

[Cheechako]

I guess if it works just use it. But surprised there is no evidence of squeezing of the material, although it comes in different densities. Are you sure there is no depression in the starboard and that's part of the problem? I suppose the actual load with 4 mounts is very low. You could just use steel too, as your motor mounts are steel anyway.

[DougR]

In all probability the shims that you currently have are adequate for the load, but if you have concerns about their suitability, replace them with something with higher density. This could be aluminum, steel, or perhaps as mentioned, G-10.

There is also a compound called "Chock Fast", which is a pourable compound made for shimming heavy industrial machinery as well as marine transmissions and engines. It is normally used for solid mounted heavy commercial engines, but would work fine on flex mounted engines, depending on the configuration of the flex mounts.

DougR

[Squanderbucks]

Doesn’t sound like the shins are the problem. Your engine mounts are worn out. These need replacement. Try and buy some that are tall enough that you can do without any shims. If not do not use starboard. As mentioned it is not dimensionally stable. Oak is what I would use if over 1/4 inch is needed if thinner use some pre fabricated fiberglass sheeting like that from Jamestown distributors of Marine supply. It comes in various thickness. Very dense and strong. Could be epoxied in place.
3/16 is a great distance tone out of align from the last time checked. Usually changes are measured in thousands of an inch. 3 to 5 thousands would be ok.
Block up engine in close alignment and attach the new mounts at midpoint of their alignment level and see if any shims are needed. If so remove mount glue in shim and bolt down the mount. Do that for each one. Then doe the actual alignment using a feeler gauge between the couplers.
This can be a big job but no way around it and takes a lot of patients with fiddling back and forth to get the alignment where it needs to be. May want to farm out this job.

[sandiegoskipper]

Don't use metal and don't use raw exposed wood. Both will degrade in that environment and you'll have a mess. Stay with fiberglass or HDPE plates. Also, if your alignment was true 2 years ago, how many hours have you put on the engine since then? Call me a skeptic, but could this be a case of the yard trying to create some business?

Skip

[stormalong]

When I repowered the engine supplier told me not to position the engine high up on the adjusting screws. He said the lower the better. I cut shims from aluminum plate of the appropriate thickness to achieve this. That is what I would recommend.

I wonder if mounting the engine high up is the cause of the failure. Being high means more of a leverage arm and more flex of the rubber.

[Wotname]

Originally Posted by JPS27

Long story short is that my trans and shaft couplings were found to be out of alignment on my recent 2yr-haul out. I have an ericson 27 and a Yanmar 2qm15. Neither I nor people I know who know what they're looking at can figure out why the engine was out of alignment from the last time it was checked (2 yrs ago, new prop install). But the engine coupler is low to the shaft coupler by about 3/16". One thing that is clear is that the mounts need replacing and that they were adjusted to their max height.

..............

Originally Posted by stormalong

.........
I wonder if mounting the engine high up is the cause of the failure. Being high means more of a leverage arm and more flex of the rubber.

This struck me also. The OP should (if at all possible) get the engine sitting low down on the height adjustment.

Rework engine bed, shim or whatever but you don't want the engine high on the mounts. Your 2QM15 isn't the lightest or smoothest engine around and can hard on mounts at the best of times.

[BlackHeron]

Alignment will change when you haul out. Don't try to align an engine on the hard, only when in the water. Hulls flex and sit differently on stands and the shaft alignment will be off.

[jimbunyard]

If you have these type Yanmar mounts, the 3/16" sag is likely because they're worn out. Believe there are some polyurethane mounts that last better, but they may be harder, and thus transmit vibration into the hull more efficiently. Depends on your specific application though...




Some different materials for shims, worst to best:


Uncoated fir or oak, compresses and rots

Resinous yellow pine, compresses but not really too bad, hard to come by

The denser tropical hardwoods, compresses, hard to come by, expensive

Steel, rusts, can change alignment, cheap, relatively difficult to machine

Aluminum, corrodes, not as bad as steel, relatively cheap if you find the right supplier, easy to machine

UHMW, corrosion free, cheap (scraps on Ebay) easy to machine, a little soft

GP03 expensive, corrosion free, good but overkill

G10 ditto

HDPE, don't buy Starboard, which is the same thing, cheap (Ebay) corrosion free, easy to machine, significantly harder than UHMW

Rectangles cut from a discarded, flat FRP panel, cheap (free?), corrosion free, easily machined, readily available (local boatyard), wide range of thicknesses



The advice to position the engine as low as possible on the mount given previously is very sound---but make sure you retain enough upwards movement to align the engine...

[JPS27]

There's a question at the bottom of this post if you don't care about this update. As always, I appreciate this site for the great advice. Thanks.

I'm trying to move deliberately as I figure things out. I still can't figure out how the engine dropped into misalignment. 2 years ago I put on a new prop, shaft and coupling for this 2qm15 after I had to ditch a "kaput" atomic 4. Things seemed to be great and I have run the engine to get in and out of the slip and marina, and on numerous occasions have run the engine solidly when needed on windless jaunts up to 30 miles.

This winter I realized something was not right when on a whim I used an extendable mirror to check the shaft/key/coupling connection. The key looked like it had partially rolled on top of the shaft and was wallowing out a groove in the coupling. Interesting note: when I hauled the boat and undid the coupling, the coupler bolts were not difficult to undo, that is, there was no tension that I noticed between the two couplings. I did have to tape the shaft coupling to get it off. It's all a mystery to me.

My thoughts are two things perhaps contributed the misalignment. First, the shim material was some starboard looking material that visually looks fine but maybe it compressed. And second the mounts are very shot, a couple look like there's no rubber hardly. And maybe there's a third reason that BlackHeron suggested that being on the hard is exacerbating the situation.

I'm remaking the shims out of G10 because I can get it from Norva Plastics near where I work for a very good price. I'm cut and drill those to size myself.

I've had enough people who have good reputations (this does not include the person who helped me replace the A-4) look at it and tell me I should just shim it again, and not go to the expense of raising my stringers, that I feel confident with this route. I've had no less than three independent fiberglass and/or marine mechanics I trust look at the stringers and the overall situations.

My question right now is what's the process for re-checking the alignment once the boat is in the water when the time comes? Same as before with gauge? I ask because when still on the hard I plan on doing a final check on the shaft position relative to the stern tube by loosening the hose and nuts to slide off do a visual check that shaft is centered. I obviously won't be able to do that check in the water. Thanks.

[Wotname]

Where did your current engine mounts come from?
With the used 2QM15?
The old atomic 4?

If with the 2QM15, they may have been worn out before you fitted the engine!
If they were the old ones, it almost certain they would be unsuitable for the extra weight / vibration of the 2QM15!

If they were new, did the supplier know they were for the 2QM15?

Alignment is carried out by unbolting the flange coupling between the output of the gearbox and the prop shaft and moving the engine until the two flanges perfectly align. There are several (many?) threads on CF about the best way to do this

Do an alignment first on the hard and then redo after launching.

[stormalong]

In addition to what Wotname said: Tune your standing rigging and wait a day or two before checking the alignment. Check again about a month after that. Then you should be good for a long time.

If you have room for it a flex coupling would make the alignment less critical.

[jimbunyard]

Originally Posted by jimbunyard

...The advice to position the engine as low as possible on the mount given previously is very sound---but make sure you retain enough upwards movement to align the engine...

Duh...upwards should be downwards in the above sentence...

Originally Posted by stormalong

...If you have room for it a flex coupling would make the alignment less critical.

Only if you have a true flex coupling designed to allow for engine misalignment.

'Flex couplings' made to absorb drivetrain shocks or provide electrical isolation require the same preciseness of alignment as do normal companion flange couplings...

[Dsanduril]

Originally Posted by JPS27

My question right now is what's the process for re-checking the alignment once the boat is in the water when the time comes? Same as before with gauge? I ask because when still on the hard I plan on doing a final check on the shaft position relative to the stern tube by loosening the hose and nuts to slide off do a visual check that shaft is centered. I obviously won't be able to do that check in the water. Thanks.

We measure the clearance between the shaft and the bilge just in front of the shaft log. Actually make reference marks and write the dimension on the hull inside the engine room. The closer you can get to the stern tube entry the less likely there will be geometry changes between dry and floating shapes. Even with a crude measurement you can get within a couple of millimeters (and you can get better if you're careful) which should still leave you pretty well centered.

We had a drip from the back of the shaft log that turned out to be the engine settling on its mounts and the shaft wearing on the stern tube. Got a toilet seal (soft wax) at the hardware store and used that to seal between the shaft and stern tube on the outside. It is then possible to remove the shaft log/seal in the water and check/repair. Maybe not for the faint of heart, but I've been through this process now a half-a-dozen times on various boats without any issue. When everything is put back together snorkel back down and clear out the wax. If you use a backing ring of packing/rope/foam backer rod this is pretty simple.