Knocking noise, can't figure it out
 

I can't seem to figure this out. I have a clunking/knocking noise coming from the transom. It is really obvious at idle. I am pretty sure it is not coming from the coupler and the u-joints were fine when I pulled the drive and merlin540 just put a gimbal bearing in it a few weeks ago. I appears it is coming from inside the bellows, but that doesn't make any sense to me. It's not like there are alot of parts in there. Allignment is dead on and the outdrive shaft is all the way into the coupler, as far as I can tell. At first I thought maybe the ujoints were getting bound up, maybe that is the case still.

Any ideas? It is not on a rythym, more inconsistent, like something is being knocked around. Pretty loud as well. Has me confused, any suggestions would be great. Not sure what brought it on, it has been doing it for a while, I just thought it was normal racket being made.

Thanks for any help or ideas...

Allan:)

Do you have the "Y" exhaust pipe that goes down to the through prop exhaust? If so, there are flappers inside the "Y" that can make alot of noise at idle.

Allan4,

What position was you drive in? I've noticed a "rattle" out of both of mine , if they're trimmed to the max. This is how I usually trailer it. If I start it in the driveway or even at the ramp without lowering them to a civilized level they'll do it. Lower them a bit and it stops. Replaced one drive last spring with a BRAND new one...that does the same thing:rolleyes:

No, I go straight out the back...Gil's. It is more of a clunking sound. Like something is rattling around. I know the transom assembly makes some noise, but this seems excessive.

Thanks though....;)

Ohyeah, forgot to mention, 24 Outlaw, B1 1.50. Thanks

Mopower, the drive is within running tolerance. It is one the trailer right now, so I cannot drop it all the way down, but it is under the trailering level and at safe operating range. It's gotta be something simple like that.....just not that many parts back there. I think maybe the u-joints are bound up and shifting and hitting eachother or something, I just can't think of anything else.

Oh yeah, I have dual ram hydro assist on it, so it is not the drive shaking back and forth.....

Thanks guys....Allan

Sounds best to pull drive and recheck the u-joints. Then at least you can run motor on the hose w/o the drive on and either eliminate or blame the drive.

Yup....guess I was pretty stupid not to think of running the boat without the drive when the drive was off. Good idea,I guess that would be one way to check the coupler....hhmmmmmm, wish I would have thought of this a week ago.

Thanks, I'll try that and see what happens

Any other thoughts??

Are you sure it's not the flappers in the exhaust tips???
Some are counter weighted and silicone coated SS. When the silicone wears off, they can make a lot of racket. Just put your hand on the the exhaust hose at the tips and you'll be able to feel it.

Like giff said the internal exhaust flaps can make quite a racket. It is more noticable at idle because of the of the spaced exhaust pulse. However it is more of a clank than a knock. You still might want to look there first since it is easy to check.

I'm gonna say internal flappers also.

You might want to pull the top cap and end cap on the drive and count the teeth on the upper gears. A chipped toth makes a pretty loud noise(BTDT). also check the amount of backlash by putting it in gear and shakin the prop. Excessive backlash makes a knocking sound at idle in neutral as well. Hope for your sake its just the flappers though.

I'll check the backlash, but after digging around more today and consulting a buddy, we are pretty sure it is the flappers. Infact, that was the first thing he said. We looked at everything else. You can feel it when you put your hand on the transom or on the 4" black tubing that attatches the riser to the thru hual exhuast port, you can feel it beating around. You can't feel that if you put your hand on the drive or the coupler housing.

I guess I need to replace them? They make a ton of racket and it aggrivates the hell out of me.

Glad it seems to be something simple, thanks for all the good advice guys...check454....right idea, wrong pipe:D :D

Good flappers always make noise. It's becuse they are made of SS. The tips with rubber internal flappers are quiet, but they break apart frequently and just don't last.

Makes sense......

How do I quiet them down...or do I?

Go faster:D

You could try to pull off the exhaust hoses or remove the tips and see where they are hitting and they put some silicone on that spot or on the counter weight. You don't want to put on too much though or it won't let the flappers close all the way.

I have the "loud flappers" with the counterweights. They sort of sound like a rod knocking. Particularly loud sounnding on the garden hose. In the water they seem quieter, maybe because of additional water flow. Don't worry about it and have fun!

BT :cool:

Thunder, that is exactly what mine sounds like. IT's louder on the hose because of the echo the hual makes without the water surrounding it....or atleast it seems that way.

It would be nice to calm them down a bit, but screw it. I'll figure something out......go faster is the best advice yet.....HeHeHe.....:D :D

The are probably louder on the hose becuase of the angle the boat is sitting on the trailer. When in the water, the counter weights don't close with as much force between the exhaust pulses.

That makes good sense Griff. Never thought of that. Allan, if you just drive around about 1800 rpm with the drive trimmed up, the noise should go away :D :D

Dave :cool:

I'll keep that in mind.....:D :D ;)

Thanks for the help guys.....

I noticed what I thought was a reciprocating type noise
at the back of my transom last season.
I went as far as putting in a new gimbal bearing.
The problem still didn't go away.
I ran the boat tonight on the hose and this post came
to mind.

:eureka: :eureka: :eureka:

Yep,Yep,Yep It is the stainless internal flappers I
installed last season!!!!!!!

Take a couple of long 18" screwdrivers or something similar and insert them into the tips and try to slightly wedge the flappers open. Just put enough pressure to make them not move. Crank the boat on the hose and see if the problem goes away. My old boat did the same thing.

Ron

Allan Have you checked boarding ladder.

RC....how ya doing man???:D

I removed that pesky ladder thing a few years back.....but knowing me that is what it would turn out to be;)

RJ, good idea, but I am pretty sure it is just the flappers, I may try that though just to be sure. Thanks everyone for the replies......SSEEEEEEEYYYAAAAAAAA:)