Recently had a Nanni 37hp replace an old 24hp on a Tartan 41. Yard has checked alignment and says it is fine, but there's still a bit more vibration than before the repower
. The drive is smooth at idle up to ~1800RPM, but then begins to vibrate as RPM
exceeds 2000. The shaft, stuffing box, cutlass and prop were all replaced with the new engine
, However, the same diameter shaft was used.
Does anyone have rule-of-thumb info for appropriate shaft diameter & unsupported lengths for a given power out put? Maybe I worry too much. But has anyone else run into shaft size issues when repowering with higher power?