Engine and propshaft alignment

[BrianLynch]

I have recently removed and remounted the engine (a Yanmar 1GM10) from my Trident 24 yacht. I am now having difficulty getting the alignment between my gearbox coupling and the propshaft correct. I appear to have a small amount of movement in the shaft at the cutlass bearing end. However, I had inspected the cutlass bearing before removal and thought it seemed in reasonable nick. Now I am getting play but find it hard to believe it is in the cutlass bearing. I am reluctant to lift out the engine again in order to inspect the cutlass and I am even more reluctant to remove the cutlass from its P bracket mounting as it looks like a horrible job !!! How much play is acceptable or should it be NIL ? Any advices PLEASE !!!!!

 

[DERF]

can't comment on the gearbox / engine coupling, but I've just done the cutlass bearings (twin shafts) and it was a relatively painless job to remove bearings and replace. not as horrid a job as you think.

Be warned tho that the first set that went in were metric bearings... even though supplied and marked on the box as imperial.. so had to do the job twice.

Manufacturer has batches of bearings marked as imperial when in fact they are metric.

If you think the play is in the bearings I'd replace them its really not that difficult.

 

[eyehavit]

There are two issues here and they are not directly related.
If the bearing is flogged out it requires replacing and replacing may slightly re-position the shaft.
First, establish whether the bearing requires replacing. Determine how much displacement there is between shaft and bearing. What can seem a lot of play may be not so bad when actually measured so beg borrow or steal a dial guage. How much displacement is acceptable is somewhat dependant on shaft diameter and type of bearing. I'm guessing yours is around 1". In that case >0.5mm would seem reasonable to change but depending on circumstances 1mm may be acceptable.
Aside from the P bracket are there a fwd and or helper bearing? What is the condition?
Once that is sorted out is the time to align the prop shaft with the gearbox.