Originally Posted by Hydrospud
Need some help,
Mainship 400, single Cat 3126: We did a sea trial with an excellent surveyor. This was the first run after a new shaft, cutlass bearing, and reconditioned prop were installed (shaft replacement was a finding from the previous sea trial). The shaft vibration could still be felt when running at full speed. We could visually see the shaft seal assembly violently wobbling.
I find any information on the prop shaft assembly layout.
We put a dial indicator on the shaft near the shaft seal. We had 0.025" runout on the shaft however, when we place a little force on the shaft we had > 0.050" movement.
Does anyone know what the runout tolerance is on this type of shaft?
Is there a bushing in the haul of the boat between the shaft seal assembly and the cutlass bearing near the prop?
Any suggestions on where to go from here? We really like the boat!!
Something is obviously out of round, or specs, or wasn't balanced or adjusted properly. Suspect it's not the shaft, if new ... unlikely to be bent but easy to check with your dial indicator.
Was the shaft properly centered with the engine mounts? I suspect not, as something is wiggling. Check the engine mounts and check the alignment of the shaft where it connects to the transmission. There's 6 bolts that attach, loosen them enough to get a feeler gauge in between the shaft flange and the transmission flange. You want less than .003" difference between any of them. Can fix that with adjustment of the engine mounts. Easy to check.
I'd bet that .025" is too much and for sure .050! I don't show the specs in my book. (I have Yanmar, not that it makes much difference).
You've replace or overhauled most everything, but didn't mention the alignment to the tranny... I'd start there.
And, did the prop shop balance the prop and give you a paper on the specs of the balance?
The MS 400 is a great boat, worth the effort to salvage the deal. And the Cummins is a great engine for that boat. Every bit as good as the Yanmar.