VDrive Transmission Noise?

Golfman25

Well-Known Member
Sep 12, 2009
7,587
IL
Boat Info
1998 370 Sundancer
Engines
7.4 MPI
Checked out a boat with twin 7.4 and vdrives. Had a noise that sounded like it was coming from the transmissions. Both sides. Went away as rpms went up. Big deal or no big deal? Thanks in advance.

see video
 
Sounds like something is wearing..that tightens up as the RPM's increase. I would think there is a wear item that may visit soon. How many hours?
 
Is that in gear or neutral?

Could be the damper plate in neutral or transmission in gear.
Many times the rattling sound is due to a less than perfect low speed idle. That would be normal for an engine needing a tune-up or fresh(er) fuel.
Just my internet guessing.
 
You probably have seen the posts about v_drives making a rattling sound when they are out of tune, need new plugs or wires. Hard to tell from the video if that is the sound. Mine rattle a bit at idle every spring the first time out until I can burn out the fogging oil and get the engines hot enough to clean the plugs of the carbon from the oil. Then quiet for the rest of the year. I had bad plug wires soon after I bought mine 10 years ago and gave the same sound, but engine was down on power too. Wires replaced and transmission rattle went away too.

If you are concerned you can get a transmission oil sample tested that will let you know if there is abnormal wear or other issues.
 
Check the upper unit gears. They may be getting worn down.
 
So would you: a) ask the current owner have evaluated and diagnosed before an offer or b) make an offer contingent on getting it checked out?
 
So would you: a) ask the current owner have evaluated and diagnosed before an offer or b) make an offer contingent on getting it checked out?


A if you feel there are plenty of boats available to your liking...
B if you gotta have this one.
 
Ok normal. You think it's something that needs to be fixed?

Eventually...like next time you have to pull the engines or drive shafts. You have to separate the transmission from the bell housing to get to them. The damper plate is there to smooth out gear chatter at low rpm. Typically have a set of springs/rubber "bumpers", and they do eventually wear out. They are not expensive, just a PITA to get to.

As mentioned above, get a good tune up, plugs wires, timing and make sure you have good fuel. Usually that helps a lot. If that doesn't get it, adding a few RPM to your idle might help as well. If still having issues, might be something to add to the project list. Long term, if they fail, can cause gear wear/failure.
 
My boat neighbor had a similar issue - was plugs/wires. A misfiring plug at low RPM would "jolt"things creating the noise. Up the RPM and it smooths out.
 
So looking for some advice. Supposably the first time anyone has ever heard the noise. Broker says make offer contingent on inspection/diagnosis. Ok, fine. I can assume the best case or worst case scenario in my offer. Fear is, if I go with best case, then spend the time and money on diagnostics, and if it's worst case then ask for repair (say replace damper plates), seller could say no (and have the benefit of the diagnosis). Then I am stuck. So do you offer assuming the worst case so your covered?
 
You're stuck regardless because it's not your boat until the paperwork is signed, survey is complete, and you're floating away. I assume you're getting the boat surveyed? If so, then any repair you ask for you're in the same predicament. It's his discretion whether he repairs or not, and conversely, it's your discretion whether you accept the outcome. On a situation like this, I would automatically write the contract like so -

1. Offer is contingent upon acceptable financing and in/out of water survey
2. Offer is also contingent on inspection and replacement of damper plate requiring removal of Vdrive at Seller's expense.

Owner will decide what to do at this point.
 
A couple more questions on your noise...

1. Is it the small clunk you're referencing when you put it into gear? That's normal.

2. Is it the small 'whirrrrl' noise you're referencing at idle just putting along while in gear? Again normal.

3. Or is it a rattle you're hearing at idle while in neutral? Again, normal.


What scenario are your referencing? You could go back to the boat and quickly run a couple more tests. May save you time and headaches.
 
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Coming from many outdrive boats to my first v-drive boat last summer, they do make different sounds.

From everything I've read and heard, they appear to be normal and overall the ZF transmissions are pretty stout.

I'd go with the advice given above when making your offer.
 
A couple more questions on your noise...

1. Is it the small clunk you're referencing when you put it into gear? That's normal.

2. Is it the small 'whirrrrl' noise you're referencing at idle just putting along while in gear? Again normal.

3. Or is it a rattle you're hearing at idle while in neutral? Again, normal.


What scenario are your referencing? You could go back to the boat and quickly run a couple more tests. May save you time and headaches.

It's number 3 -- rattle in neutral. Goes away with increased rpms. I have no real issues accepting that it is probably "normal." And a bonus if an experienced mechanic takes a look and say, yep normal, don't worry about it. And that is what I actually think based on experience and research. However, as this and other threads have indicated, it "could" be an engine mis, spark plugs, wires, etc. (ie; something simple). It also "could" be signs that the damper plate is about to fail and needs replaced (requiring a lot of time and $). I am going to end up paying for the diagnosis and then be at the whim of the seller to fix if it is fixable.
 

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