Proper shim material for engine alignment?

[james247]

Originally Posted by 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.

Quite simply this could explain the large out of alignment issue. Dry rot in the engine bed could also be the issue. Refloat wait 48 hours before checking as the boat takes time to change shape. If the large discrepancy is still there the engine needs to be lifted of the mounts. The mounts removed and properly inspected for failure. The engine bed checked for dry rot under the fibreglass matting. Repaired if necessary. New engine mounts with greater adjustment range should then be installed and the engine aligned to within 5 thou tolerance.

If the discrepancy disappears when you refloat then concern of structural damage of the boat should be looked for ie in a timber boat a broken/cracked rib or in the case of a fibreglass boat a crack at the raft end of the point where the keel joins the hull possibly caused by a grounding.

In my experience nothing is simple in this type of matter

[Terra Nova]

One thing to watch out for when doing the engine alignment:

The weight of the shaft and coupling extended beyond the shaft log invariably causes the shaft to droop below the nominal centerline of the stern tube. So try to adjust the transmission coupling, vertically, such that, when the shaft coupling is engaged, the shaft will be roughly in the vertical center of the stern tube.

[RaymondR]

I mounted the engine in my last boat on heavy alloy angle iron with locator pins on the fixed engine beds so that I could lift the engine out, sit it on two 4 x 2s across the cockpit seats and put it back in without interfering with the alignment. Worked really well.

[Cheechako]

Originally Posted by 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.

Yes pretty much the same, just in the water. Align it approximate while out of the water, especially with all the changes you are doing, then again as close as possible when in the water. I'm very happy if i get within .005".
If the Starboard compressed there would be an indentation in it the shape of the motor mount foot. I have seen compressed Starboard from over tightened bolts/washers a few times, they always exhibit this. While Starboard does "squeeze" a bit, your engine is very light weight. With that load distributed over 4 feet, no problem. I might worry more how slick Starboard is.
I was amazed the rating of universal motor mounts when I looked for some for my Generator projects. A little 1.5" diameter mount is good for like 150 lbs or something like that.

Regarding your shaft key, if it is rolling in the groove you have the wrong size. Maybe you have inch and need metric or etc.? It should be so tight you have to lightly tap it in the groove.

[Hoohaa]

I will be using a 10mm one of these panel packers for raising my mounts. They are made for concrete tilt panels so can definitely handle the weight of the engine. and they are available in many sizes.