|I posted a question the other day regarding my circulating pump. Well I believe the problem is in my tranny. We were out the other day and I got in the water. As soon as my friend went to take off, the boat hesitated and started to bog down, wouldn't plane out and there was a loud bang. I got in the boat and we were unable to get on a plane. I ran the boat in my driveway and when it is put in gear there is a loud noise coming from the tranny where the shaft goes in. This noise starts out quiet at first and then builds after a couple seconds. But the boat goes in and out of gear with no problem. Any ideas what the hell is going on here. my guess is that we hit something underwater (the bang noise) and the shaft was bent causing us to not be able to get on a plane, hence the loud vibrating noise coming from the tranny. I know it is hard to describe but any input,costs,parts would be great|
|The loud noise might be your shaft packing burning up. You should not put your boat in gear without it being in the water (there is no other way to say this, so here goes) Your shaft uses the water as lubrication without water, you'll burn up the packing and cause damage. You may or may not have transmission problems. It sounds like a fuel delivery problem to me. Have a professional look at it. Your insurance should cover you if you hit something and damaged the shaft and tranny.|
|If it is the shaft packing, what are we looking at for price to fix..It was only put in gear in the driveway to see what the problem was from when we were out there. Definetely not something I practice all the time. |
|can you disconnect the output shaft from the trans and run the unit -- see if hte noise is still there... it could bea fue delivery problem --but very unlikely w/ the noise you are describing. however if you hit something in the water, yoou should have somewhat felt it, not just heard it. but if hte shaft is bent AT ALL you DO NOT want to run the trans w/ the shaft connected...|
|I would be really surprised if the shaft packing would cause that symptom. |
Like Troy said, the prop shaft uses the water as lubrication so it is a really BAD idea to run the prop on the trailer. The shaft packing may tolerate it for a while but the cutless bearing could get destroyed.
The cutless bearing is the "bushing" that is in the strut, which holds the shaft just ahead of the prop. In normal operation the strut is completely underwater. Groves in the bushing allow water to flow down the length of the bushing and creates a film of water over the shaft as it turns.
When you operate it dry the friction will quickly heat the bushing, make it expand, grip the shaft tighter, bind, make noise, tear itself up, etc.
Try turning the prop by hand. You should be able to turn the prob with only a minimal amount of resistance. It should also turn evenly throughout the complete revolution. If you have to really lean into it to get it to turn then something is very wrong. If the shaft turns freely for a bit and then binds then it indicates that the shaft is bent or out of alignment.
It doesn't take much of a bend on a prop shaft to create so much vibration that it can seriously damage things. Generally, however, the boat will still run and perform, it just will shake itself apart.
If the shaft is bent so bad that it is binding to the point that it is dragging down a 300 HP engine then I would expect it to be fairly visible to the eye. Turn the prop and see if it wobbles or if you can see any run out in the length of the shaft.
If you are not sure then pull the shaft out and take it down to a shop and have it tested.
It is also possible that something really bad is happening in the transmission. If the clutch was slipping it could fool you into thinking that the engine was bogging down.
Pull the dipstick on the transmission and smell it. If it smells burnt then just give a heavy sigh and repeat: BOAT = Break Out Another Thousand!
|Sounds like the bang could have been a backfire from an ignition or fuel problem. I'm not sure what your maintanence history is like, but I'd be inclined to change your fuel filter and water seperator, then maybe drain the fuel from the fuel rail and start fresh. |
Nothing like getting internet diagnosis, though. I agree with the above statement to bring it to a professional boat tech.
|The boat is at the shop now, I think that the noise in the tranny is just from running it on the trailer. As it doesn't make any noise at first and then after a few seconds it builds to a loud ass noise. I had an issue the day before where we rode all morning, went to the house, then relaunched an hour later and the boat wouldn't start. This boat usually fires up at the drop of a dime so this was weird. when I got back to the house I put the hose on it and after about twenty tries it finally started back up and ran fine. it was the very next afternoon that this issue happened where it would't come up to speed and then came the bang. Unfortunately I wasn't in the boat and I can't be sure if it was a backfire, but that is what I am thinking. Fuel problem and not tranny, I appreciate all the help and once again this website proves to be a enormous help! lets all pray for a low mech bill tommorrow!!!!|