1998 Moomba Kanga with intermittent noise

[moombakanga]

I've got a 1998 Moomba Kanga with 75 hours on it and trying to locate the source of an intermittent noise that I'm having. Its sounds like a high pitch squealing noise. Almost like a belt slipping but worse. The first time it occurred I couldn’t pinpoint where the noise was coming from. It sounded like it was coming from the front of the engine so I replaced the impeller on the raw water pump. Next trip, same noise. It seems like the noise will not occur if I'm running along at lower speeds. Once I plane out like to travel to a different part of the lake and run for a while, the noise will start. Once it starts, you can see the vent cap on the transmission vibrating and the noise seems to be coming from the transmission area. There seems to be no slipping of the transmission when this occurs. Transmission fluid level and temp all look good. The vibration that accompanies the noise is not that bad. If it were not for the noise, the vibration is so minimal that I wouldn’t even give it any consideration. When running the boat planed out and the noise starts, if I throttle way down the noise stops. If I throttle back slightly the noise continues just to a lesser extent. If I slow down and let the noise stop and then get right back on plane, the noise will return. It seems like if I slow down and wait for a while, the noise takes a while to return once I get back on plane. I thought maybe it was cavitation but it seems like the noise would go right away once I dropped the engine speed some if this were the case. I have looked close at the shaft. To the naked eye it looks good and straight. The rudder ??? that the shaft goes through and it holds the shaft at the bottom of the boat looks straight and no apparent signs of hitting anything. The rudder is solid and wont move if you put pressure on it. The bushing that supports the shaft through the rudder (cutlass) shows no slack side to side or up and down. Again the boat has very low hours for its age but that really means nothing.... The prop is dinged up some and one blade looks a little bent at the end. This is on my to fix list. I dont know if the prop would set up this noise or not.. I decided to try to get the sound to re-occur while on the trailer. Realizing that there would be no load on the shaft, transmission as you would normally see while on the water, I wanted to try anyways. I set up the water to the engine, water hose to run on the rudder to keep the Cutalss (?) bushing / bearing cool, one hose to spray on the shaft nut / packing from the bottom of the boat. Lastly one more hose to run on the shaft nut packing from inside the boat... Cranked the boat up and ran it at higher RPM's for more than 1/2 hour and just as I figured it was flawless ...no noise. I'm not sure who to try to call for advice. I’m down on the Gulf Coast in Texas and its hours to the closest service. I’m sure this kind of diagnosis can get pretty pricey. If anyone has any suggestions please reply... Thanks, Cliff

[lowdrag]

First off, I would highly advise against running the boat in gear while out of the water. For obvious reasons that you already stated, no load, you didn't hear the noise while doing this. As of right now I'd say repack the shaft bushing. If it wasn't bad before, I'd bet that it is now. Unless you took some measure other than just running water over it, I'd bet it didn't get enough to keep it lubed. The pressure from the displaced water forces the lubrication and the hose probably didn't get the job done unless you found some way to rig a pressure fitting. From there, I'd get the prop fixed and balanced and check the allignment on the shaft.

[moombakanga]

Thanks for the reply. I know that my method of cooling was pretty primative and like you say may not have been enough. If I understand correctly your supposed to have the packing reworked at 100 hours so I may be having to do mine a little early... Shaft packing one issue and then you mention shaft alignment so are you thinking that this may be my source of noise. Of course shaft alignment is very critical and i'm sure if its off it can cause a lot of problems. If the shaft is out of alignment, do you have any ideas where the squeeling would be coming from? Anyone have any rough ball park figure as to what it costs for packing replace and to check shaft alignment?? Thanks in advance for any input. Cliff

[lowdrag]

Those were basically just some ideas of things that would be cheap and easy to have fixed or do it yourself. The shaft packing you can definitely do yourself. I believe some of the guys here have done the alignment themselves, but I've never tried that one.

I'm just making the assumption that the problem is not tranny related since you don't seem to be having mechanical difficulties with it. That and the noise you describe is similar to what a lot of others have described and it usually ends up being the packing.

Is the boat new to you or have you owned it since it was new. If it's new to you, maybe the person before you either repacked it or tightened it a little bit too much. Several people have complained of a similar noise on new boats that usually disappears after a little break in.

Could be any of those issues as all of them could cause the shaft to exert extra pressure in one direction thus causing a squeeling sound.