This question is specific to the '09 X1 with MCX. We have had ours now for 3 1/2 years (from new), and from the very beginning it has had a vibration from 800-1300rpm that shakes the steering wheel, the dashboard, windscreen, and the tower. The vibration isn't horrendous, but it is enough to make the windscreen and steering wheel rattle, and boards in the racks shake.
Most people will say "must be a shaft/prop issue", but this occurs also in neutral. The vibration is prominent enough that 90% of the people who come into our boat will comment on it and wonder if the prop is out (then they realise that we are in neutral). It does appear to diminish above this rev range and is not noticable at wakeboard speeds.
We have had multiple marine mechanics go over this, and multiple theories. Unfortunately our local dealer went out of business soon after our purchase (and this may have meant that our issues were not communicated to Mastercraft properly at the beginning), but our local service agent has been dealing with Indmar and Mastercraft for well over 2 1/2 years now, and we had a replacement engine sent over (no difference), then a new transmission (no difference). Then everyone got concerned over oxygen sensors and injection mapping (but no answers).
The most recent development was a Mastercraft Engineer from Australia flew over to deal with the problem. He adjusted the tower (which was out of alignment - and is more solid now), and told me that this vibration was completely normal for the '09 X1 with MCX (apparently the EXT CATs required a different cam and ignition profile to get the power up after the cats were added, and this has resulted in a 'lumpier' feel at lower revs), and it is unique to this model due to exhaust harmonics and the narrow hull setting up a vibration.
I'm struggling to understand this, and how a boat that feels like this on the water could be sold as an example of the quality that Mastercraft represents. Before ordering this one, we test drove an '07 X1 (MCX) that was smooth, and recently I have spent some time in an '06 X1 (MCX) that is silky smooth over this rev range. I have never been in an inboard (and I've been in a lot) that feels like this.
I love our boat, but have concerns that this vibration could be causing some long term issues, and although I am not planning on selling this soon, when we do come to sell it this vibration will be seen as a problem (I know I would, and if I was looking to purchase a 2nd hand boat - I would be wary of buying this one).
We now have 375 hours on this boat (so it hasn't stopped us using it, but we would normally put 180 hours a year on - there has been a lot of time when it has been unusable while mechanics have had their heads in it, or parts out of it).
I have searched internet forums ad nauseum, and found no information. I have held off posting this in the hope that I could work with Mastercraft to find a solution, but now I just want to know if anyone else who has this boat (or has spent time in one) has the same issue (or am I being fobbed off).
I have no doubt that if I was in the US, this would have been dealt with long ago (even if it was a matter of putting it on a transporter back to the factory), but down here in New Zealand it is a bit more difficult.
I would welcome any opinions on this (it is specific to the 2009 X1 with MCX engine) - and if other owners tell me it is perfectly normal, then that will at least give me an answer.