Motor mounts

[Elcojo]

Hi all,

I am new to the forum and owning a boat. I have been researching about replacing motor mounts and shaft alignment a lot. We have a catalina 27 with a 5411 universal diesel, the engine mounts were all bad and in one of them the nut was completely loose.

I have been able to lift engine and install new mounts. The question I have is that I have align the engine with the shaft coupling up to 0.05" but the mounts moved towards the aft almost 1/2". I have the older ones marked. Is it possible that I push somehow the shaft when I was trying to align it. I am sure this is the dummest question but what keeps the shaft from moving towards the aft or bow, just the motor mounts ?

Thanks,

[Wotname]

Originally Posted by Elcojo

........ I am sure this is the dummest question but what keeps the shaft from moving towards the aft or bow, just the motor mounts ?

Thanks,

Welcome aboard CF, no dumb questions here but sometimes dumb answers

In essence, most (almost all?) times the mounts prevent the shaft moving fore or aft.

Whether your shaft having to move back an 1/2" will be an issue or not depends more on how the shaft is installed and exactly where the prop is but if you move it back by say an inch or so and it turns freely by hand, then it is unlikely that moving it back by 1/2" will be an issue.

[jimbunyard]

Not a dumb question, in fact a discussion and selling point for a thrust bearing type device that removes the thrust from the engine mounts and transfers it to a flange integral to the boat's hull.

Probably the main issue to look out for in moving the engine aft is that you have enough room to change the stuffing box packing, or if you have any of the variety of alternative shaft sealing devices, to maintain them. There is often very little room back there, especially with smaller boats.

If you're moving the engine back because the mount's mounting holes are wallowed out, there are several options to enable you to use the original holes, from filling them with various materials, to using longer or larger diameter screws...

[NYSail]

When I changed mine I traced the footprint of the mount, set the new mount height to match Old and replaced one at a time so as to keep everything in place. Can you see where the mounts previously were so you could match previous location? Or maybe dive down to make sure everything has enough clearance with the prop and cutlass.
Good luck

[a64pilot]

Assuming the new mounts are the same as the old, just grab the engine and pull it the half inch forward so the holes line up and you will be fine.
Average Boat, nothing keeps the shaft from moving forward and aft or holds the engine in position, except the mounts.
The mounts also of course absorb all of the thrust the propellor generates, its one of the reasons that mounts are so important.

From the picture, it appears he was smart enough to outline the old mounts prior to removal

[billknny]

But something to keep in mind.... unless the shaft is exactly parallel to the engine bed, moving it back 1/2” will change the alignment dramatically.

Be very sure you get the transmission output and the shaft carefully aligned to the manucaturers specs (typically 0.002”). If you don’t, you will shortly be replacing transmission thrust bearings and/or have constant problems with shaft leakage.

[Elcojo]

Thanks so much for all the replies. I was able to move the engine back to the original position and re align everything again. Everything seems to be where it was before but with new motor mounts.

[Suijin]

I love a simple happy ending