Quick help with identifying noise

[CaptBob-O]

Hello all,

I am looking at purchasing a very well taken care of 2001 Tiara 3100 open with 8.1 Crusaders. 
It has passed all inspections but the only thing that i have noticed and bothers me is this:

The starboard motor while in neutral runs smooth. When put in to forward gear at low RPMs, I can hear some chattering in the velvet drive. As RPM increases, the noise gets quieter. 

Is this gear lash? Or is this something that should be taken very seriously and keep me from buying the boat?

There is zero noise while in reverse, only while idling in forward gear. 

Has anyone hear something similar in their boats?

Also, if I go through with the purchase and end up having to pull the velvet drive out, does the whole motor have to come out in a 3100, or is there enough room to just get that small trans out?

Thank you all!!!

[Eric Wachsning]

Sounds like the idle on that engine is too low, they don't like to idle under 650 and when you put it in gear it will drop by another 100 rpm which will increase the chatter. It also could be the engine needs to be tuned up and / or timing checked. If the motor is not running perfectly it can cause backlash that you will hear in the trans. It could also be the damper plate is getting worn and will need to be replaced. This is not super expensive but the trans will have to be pulled to do this job and then put back. In summary try raising the idle to around 700-750 when in neutral and see if the noise goes away when putting it in gear. Considering you have not bought the boat yet this would cost nothing to check. If this does not cure the chatter then I would have the seller check the timing on his nickel. Hope this helps. I had the same issue on my 31

[CaptBob-O]

That’s some good advice. 
Can the idle be adjusted on a MPI or only on carberated engines?

[Eric Wachsning]

Sorry I did not pay attention to the year of the boat. I don't think the idles can be adjusted on those engines however there has to be a reason for a low idle so I would suggest having a mechanic scan it to see if the idle is low on that engine and if so why. Sorry for the misinformation earlier, I'm still stuck with carbs.

[rcwiegand]

I have a 2004 35 Open with 8.1L's The starboard trans has whined since day 1. There is occasionally some chatter at idle with the rudders turned. All goes away in reverse or at higher idle. ZF service said the whine is normal on the starboard because of the counter rotating. I have over 2000 hours on the starboard trans-nearly all idling/fishing hours. Love the engines and the boat!

[CaptBob-O]

You guys have all made me feel so much better about the purchase. After reading and speaking with mechanics on this issue, I have made the decision to purchase the boat. I should take possession of it next week!
Its been my dream boat since day one, and its taken me 7 boats to get to it.............FINALLY!!

[reeltimebrad1]

Congrats on the boat and dont worry about the clatter if it bothers you alot you can put heavier weight oil like 15-40 rotella in and it will totally silence the noise. Its something alot of ski boat guys have been doing for years without any issues. The noise is usually coming from the straight cut gears if it dissappears with a slight rpm increase.