Sudden vibration problem

[wakedriver]

We store our Mastercraft prostar 209 in a drystack on a lake. We were out last week and all was as fine as anyone could wish. Yesterday, we went out and, as usual, let the boat run at very low speed (rpm around 1000-1500) until the motor was up to temperature while we exited the no-wake zone around the maria, got the towrope attached to the tower and all of the other little preparations. In retrospect, as we were traveling at low speed (<5MPH) while exiting the marinas no-wake zone, I did feel something strange sort of like bump but not really like we had hit anything. We were in a cleared channel in 27ft of water at this moment and were right near the line of buoys that demarkate the no-wake zone. There was a slight, wind-driven (4-6inch) wave pattern on the water and after looking around and not seeing anything that we might have bumped up against, I decided that I had just felt the boat slightly slap one of these small wind-caused waves. There is very little floating debris in this lake and in 70 to 80 hours on the water, I have never seen anything like a log or branch floating on the waters surface. In that time we have seen a total of 3 beverage cans (two of which we were able to recover) and 2 plastic bags (one of which we were able to recover). While it is possible that there are submerged logs floating in 27ft of water at a depth of around 1 foor below the surface, I think this highly unlikely.

When I advanced the throttle and brought the RPM up above 1500, there was an unusual vibration that was shaking the entire boat. The boat and we have 40 hrs on us and, while I am becomming more attuned to the sounds and feelings of this truly fine boat the more I pilot her, this did not seem to be a "new awareness" but rather "something wrong". The actual performance in terms of speed vs rpm was about correct, but acceleration was less than normal and this just felt wrong. The water was almost smooth as glass and was, in fact, the smoothest we had ever seen it. My wife noticed the vibration and agreed that it was both new as well as feeling unhealthy (and she is blessed with a strong sense of mechanical "right and wrongness": as in knowing by feel when a bolt is as tight as it should be). We stopped, opened the engine hatch with engine running, and looked for anything wrong. All looked fine. We stopped the engine and I grabbed and shook everything that I could imagne might have come loose. Nothing was loose. I looked over the engine mounts and shook them by hand (not that expected any of them to move much by hand with a 5.7 liter engine sitting on them but if they did, this would be a clear problem) They all felt tight. I checked that all ignition wires were well seated at the distributor (could not reach the plug ends without too much contact between my arm and the hot manifolds) This just in case I was running on 7 rather than 8 cylinders although it did not quite feel like that.

While I watched the drive shaft,packing nut, and everything else that I could see in the engine comparment, she started the engine, engauged the transmission in forward and brought the boat up to the speed where the vibration was obvious. Everything looked fine. It did not feel fine. We opened the hatches that give access to the rudder shaft and actuation mechanics, shook it by hand and felt notthing loose. Underway, there was no water leaking around the rudder shaft and just the appropriate drops of water around the drive shaft.

We stoped again and turned off the engine. She went over the side and swam under to check the running gear for anything unusual. She reported that there was no forign material hung up on the prop or the rudder and that she did not feel any looseness when she grabbed either and shook it. She had asked me it the prop were sharp enough for her to worry about it. I that no, not unless I had hit somthing with it and caused a nick in the edge. Upon returning topside, she reported that all felt OK, and looked ok as be she could tell without a facemask or goggles but that I had failed to warn her about the cotter pin at the prop and that it was indeed very sharp on its tips. OOps. She was not bleeding too much and had not lost her sense of humor so we went around the boat just looking for something to blame this problem on. When we put the boat away (or rather when we return the boat to the dock and ramp where the marina operators put the boat on the forklift and take it up the hill to the drystack, we have to lower the tower and we put the cover on the boat to keep down the dust. Since we raise and lower the tower everytime we take the boat out, at this time we double checked the four knobs that secure the moving parts of the tower and I looked at the four large allen screws that serve as hinge points for the tower as it is raised and lowered. A couple of these felt a little lose (as hinge pins must be to some degree) but while underway, the vibration did not seem to come from the tower (I have experienced this vibration when I forgot to tighted one of the securing knobs and that vibration is of a much higher frequency and just does not shake the entire boat as this was doing). The bilge was dry. The balast tanks were both empty. We could not find anything massive that was not secured very well. The gas tank was half full (about 20 gal) and the straps that secure it all felt tight. There is no powerful subwoofer system emitting a strong subsonic signal (only half kidding, I have encoutered sound systems on boats that could fool me into believing that there was a mechanical source of the sound). While we probably should have gone back in, we decided to try a couple of wakeboard runs so at least the commute to the lake (one hour each way driving considerably above the speed limit) would have been for some riding time (and also because I wanted to see if this vibration would change as somethings warmed up (like the packing grease...admittedly a long shot)), we did some wakeboarding.

My wife rides, I drive. We both like this arrangement. Trust me, I really really enjoy piloting and driving vehicles. Not so fond of being in the water myself although she is having so much fun that I will get around to it eventually.

It was right near sunset, the wind had stopped, and we had this part of the lake totally to ourselves (which is rare) with the exception of one fisherman in a bass boat but he only passed us once and other than our own wake, the water was like glass. If we stay in this particular the narrow creek off the main lake, the total wakeboard run befor turning (and there is room to turn at either end) is about 1.5 miles. We made this run about 5 times before going in. At no point did the boat change its vibrating behavior. She reported that everythin looked normal from her perspective 70 ft back. She boards at between 18 and 20 MPH (about 2100 RPM) and the boat was vibrating significantly at this speed. Without PerfectPass, the speed does typically vary between 18 and 21 MPH if I am distracted by filming her (which I was yesterday, but she tolerates that variation without (much) complaint. She said that she did not feel the vibration through the towline and that surprised me (also leading me to further discount the idea that the tower was the cause). When we headed in (about a 2 mile straigh shot up a 1/4mile wide portion of the creek, I decided to see how the vibration and the boat responded to higher speed. The top speed of our boat is around 45MPH an is typically smooth as silk (or at least is as smooth as the water) up to that speed. Yesterday, when we got to 30MPH on glass-smooth water with no wind at all, we could not tolerate the vibration. It was just getting worse with speed. Normally, there is no need to hold the wheel if going straight. It just tracks straight. Yesterday, when I released the wheel, the wheel would begin turning as the boat pulled off the straight course to port. This was new and obviously wrong. As we returned to the marina, I ran out some minutes of video with the camera looking to stern an zoomed in and out (I like to have some header and trailer footage for my home wakeboarding videos.) Upon reviewing this footage last night, the wake is not symmetric: it was higher and was breaking on the side opposite to the direction that the boat was trying go when pulling with my hands off of the wheel. I cannot sweare whether this footage was made with the boat going straight (my other hand holding the wheel straight) or with the boat being allowed to turn off course. We returned to the marina a few minutes after closing and left the boat at the dock by the loading ramp. The staff consider this a normal option for members who want to stay on the water past closing time and they just pull the docked boats an store them befor they open the next day. I had really wanted to get a better look at the underside of the boat while they had it up on the lift, but did not have that opportunity. All looked fine during my typical short inspection as the boat was brought down to the water at the beginning of our trip that day. One additional fact: I am absolutely certain that I did not hit anything (like a stump or rock) with any part of the boat on the previous outing or before we noticed the problem yesterday. Last week I returned to the marina by a 5 minute run at high speed (>35 MPH) just for the fun of it and so that the engine could streach a bit. This is still only around 80% of max. The no-wake Zone surrounding the marina is large and the slow navigation to the ramp allow the engine to cool down to idle temperature before putting it away. Actually, I have never noticed more than 5 degrees (F) of engine temp variation between high and low speed running. In addition to the dry doc, the maria also offers in-water slip storage and so we observe the no-wake zone carefully to avoid being rude and causing the in-water boats to be buffeted against the slips.

Those are the facts. Now for the speculations.

After all of the checking that we performed, I can only come to a very short list of potential causes of this vibration.

In fact all I can come up with is A)a motor mount has failed, B)the mounting of some other component of the drive train support has failed; C)the prop has become bent or out of balance; D)the rudder has become bent in some way.

A and B could occur in a "natural" way (as in spontaneous without human intervention)but if a motor mount is in fact defective then this just "happened" between the time I shut it off last week and the time I accelerated to 1500rpm yesterday and the same goes for the rudder.

Leaving the possibilities that are "natural", C or D could occur if 1)yesterday while traveling at <5MPH near the bouy line marking the no wake zone I did hit something submergedl or 2)either when placing the boat into the storage berth or removing it, the lift operators struck the running gear (the rudder and/or the prop/shaft/mounting) onto something somehow. There are actually very few ways that I can imagine that this could be done without also damaging the hull in a way that I would have noticed when the boat was brought down to us yesterday. The lift operator has to drive down a moderately steep and long ramp and the hull is easy to observe in a causal manner and I always do. We looked over the entire hull and gunnels above the water line when we returned and my wife did not observe any hull abnormalities when she did her underwater inspection. Admittedly, she did not have goggles or mask and the water visability was only a couple of feet and she was concentrating on the stern area where the shaft, prop , and rudder are located. The hull is white and since it is not stored in the water, it is clean and clear of algea growth. 3)In between our excursion last week and our excursion yesterday, someone with access to the lift (and competent with it) took our boat out into the lake and hit something like a stump, put it back up and did not tell us. We leave the keys in the boat.

I have already described the incident that gives rise to concern over 1) and I just do not belive that what I felt could have possibly done enough damage to result in the symptoms. We feel that number 3 is highly unlikely. We have stored boats in this facility for 2.5 years and have come to know all of the staff well enough to absolutely trust them with our boat (otherwise we would not leave it there). While ours (utill the past month when two other Mastercrafts appeared) is the most "sporty" and fun of the boats that they store (the vast majority are pontoon deck boats) and, until the past month, ours was the only inboard boat out of 300+ in the stack (all others were outboards and IOs), we find it very difficult to believe that a staff member would do this. Besides, they know that if they want to drive our boat, we would be happy to invite them along anytime we go out and have infact made that offer. Not bragging, but when we brought ours in the first time, it drew so much attention that the owner of the marina, left it on the trailer (in the dry stack shed) because his entire staff (only 5 other staff members) wanted to crawl all over it and drool over the engine and just generally admire it. We had kept a deck boat (outboard) there for a year previous to this and they all knew us. They all know everyone who keeps a boat there. By the time we get out of our car, they are already getting our boat out for us.

In short, we trust them and they seem to like us. Number 3 is unlikely.

That leaves me with number 2 which is possible. It will be very tough to prove if true.

Or, my mechanical diagnosis may be incorrect and there may be some problem with the transmission that I have never heard of that is resulting in a non-symmetric load on the drive train some how. Still will require that it happened spontaneously while the boat was stored or that it happened at the moment I accellerated.

Obviously, I need to get the boat to the dealer (which is an unfortunate requires an hours trailering of the boat. Not sure how they would diagnose this one but there is a lake near to them so at least they can drive it themselves and get their own ideas. It is under warrenty so I am reluctant to let the mechanic at the marina work on it at this point. There is also the not so subtle possibility of conflict of interest in case it begins to appear that they were the cause.

This is a small, family owned and run marina. They are good and honest people who extend interest-free credit (just a note in a paper notebook) for purchasing gas and food and basic supplies that you forget to bring on any particular day. Between the time I sold my other boat and the time I took delivery of the new one, they gave me credit for the dry-stack rental even though the contract was yearly and even though they were reserving a space for me. In short, they have given me every opportunity to believe that they will act honestly if they turn out to be at fault. That said, it will be tough to prove and it would be tough for me to hand them the bill.

But I am getting way ahead of facts. Right now I need to figure out what is wrong and how to fix it.

Anyone have any ideas or experience that might give me any other ideas regarding what could have gone wrong with my boat?

[1080]

You seem ohave all the bases covered so I would suggest you just hook up to your car abd take the boat to the nearest tournemant boat dealer MC or not and get them to diagnose/fix it.

I personally would not run my boat if it did not feel right!

[wakedriver]

Good advice (and I agree with it). In retrospect, I would not now have taken it for even those few short wakeboarding runs. They did give me a bit more information though as well as video documentation of the asymmetric wake.

Thanks for the reply and I fully support your statement that if the boat does not feel right, don't run it. The closes tournament boat dealer/service is only about an hour from the marina and IS the MC dealer where I bought it new this past spring. It is scheduled for service at 50hrs and has 41 so the timing is not bad for a visit to the shop.

[Tower_boy]

even though it doens't feel like you did i'd put money on your shaft/prop being out of shape from a light collision - it really doesn't take much to damage a prop when its spinning at 1000+ rpm

I think you must have just tapped a log with a prop blade - do you know if it is a stainless prop or a brass? if stainless then i'd bet your shaft is slightly bent (pray its not as they are about $1800 to replace 8O :cry: ) if its a brass prop then it sounds like it needs truing back to shape... more like $20

I'd bet whichever it is, they can't be that bad as the boat was still running in the low revs fine, however as you speeded up the vibrations increased.. which would point to unbalanced underwater gear.

As 1080 says - if it don't feel right don't run it.. you oculd have damaged your bearings and seals by running it once the problem had shown itself.

Have it checked and trued and you will be back in business

[drivesalot]

I think we could do with a little more detail

[Tower_boy]

drivesalot Was that a joke.. the dude wrote like 6 pages!