knocking tranny at idle

[TravisFling]

Hey all,

At idle speeds I'm getting a knocking sound, only in forward. Anything above idle it doesn't do it and not in reverse either... It's not affecting performance at all, you can just hear it. I was wondering if maybe the boat it going faster than the propeller, and that's the sound of it slowing down? Any ideas?

Travis

[djbartholomew]

RE: knocking tranny at idle

Well I would think that if you have every many hours on the boat that it could be the start of the strut bearing wearing out. If it is it will start knocking when turning at slow speeds next and then you will see that you can feel a little movment of the drive shaft. this will take about 50 to 100 hours to go from the slight knock at idle to the slight movment of the shaft. Good luck finding the problem

[Fatboy206]

Knocking at tranny

Had the same symptoms on a friends boat recently, one of the forum guys told me to check for a loose prop and that's exactly what the problem was. Let us know what you find out.

[Fatboy206]

Knocking at tranny

Had the same symptoms on a friends boat recently, one of the forum guys told me to check for a loose prop and that's exactly what the problem was. Let us know what you find out.

[Sbt3]

RE: Knocking at tranny

Don't know how your boat is but I was recently in a newer vlx and there was a set screw that had come loose on the coupling and was hitting the housing when it rotated around. You could only hear it at idle as well for some reason. I'd check all the bolts in the coupling and make sure they are tight.

[TravisFling]

RE: Knocking at tranny

Great and thanks for the advice. I will give that a check-out tonight when I get home and see if it's one of those... hopefully it's one of those as opposed to the strut bearing.... I shall see.

[TravisFling]

RE: Knocking at tranny

checked it out last night and here's the synopsis. It didn't do it when I first started it, and then started when I idled later, meaning it had warmed up. Then I shut it off for 1/2 hour and didn't knock, and then did it again after it warmed up. It only does it on idle speeds in the no wake zone. I checked the prop and it was tight as a drum. I checked for loose set screws and found nothing visible. I'm guessing then it's probably this Strut Bearing? Anyone have any information or diagnosis on this, or advice on how to fix it? It's a 1989 with 750 hours. I'm the second owner and it's led a sheltered life. Should I be checking the transmission fluid for a low level there?

[TRBenj]

RE: Knocking at tranny

I wouldnt think its any of the problems previously suggested. Whats your idle set at? If its too low (less than 600 RPM) then the damper plate will knock. If the damper is starting to go, then it will knock even if the idle is set properly.

[TravisFling]

RE: Knocking at tranny

Hey buddy!!! How's that boom? The idle in gear is the same as idle out. I think it's about 900 or so? It's weird that it only does it intermittently, though. Seems odd to me. I had the luxury of towing my buddies pontoon last night (go outboards!!!) and it didn't do it all, despite idle speed for over an hour. It always runs perfectly, it's just a noise...

Travis

[TRBenj]

RE: Knocking at tranny

Boom is great, thanks again.

900rpm is actually a bit high- it should be closer to 600-650rpm in gear. I suspect you may be due for a damper before too long.