sx cobra rattle/vibration noise

[fisherman73]

Hi guys, I noticed after being on plane for about twenty minutes or so when I come down and put the drive in neutral I have this rattle type noise that is fairly pronounced that will come and go when I engauge the drive into forward or reverse. The noise is only present in neutral and will fade away after about 1 minute. Any Ideas? Thanks in advance!

 

[MainstreetUSA1]

Re: sx cobra rattle/vibration noise

Will the noise be audible when you rev the engine slightly in neutral? Sometimes exhaust flapper valves (in the down tube) will rattle when the egine idles. This can happen when they near the end of their lifespan. <br /><br />Volvo actually put out a service bulletin a while back to remove the flappers due to them being ineffective. You may find other posts addressing this.

 

[fisherman73]

Re: sx cobra rattle/vibration noise

I havent tried to rev it up in neutral but I will this weekend when I am out. Do you know what years this bulletin applied to? Mine is a 97. What is involved in removing them?

 

[wingus]

Re: sx cobra rattle/vibration noise

Did you find out if the flapper was the problem or was it something else? I have a 97 volvo penta engine and have some of the same issue you have! I hope you know what it is b/c I want to fix this! thanks in advance! <br /><br />e-mail jon@wingus.com

 

[Don S]

Re: sx cobra rattle/vibration noise

You might want to check the gear lube level. Many times if the level is low or water is in the lube, you can get a backlash noise after a run. Especially if the engine is running a little rough at the time.

 

[fisherman73]

Re: sx cobra rattle/vibration noise

The noise does go away with the throttle even slightly open. I will check the gear lube but it is only months since I changed it and see no signs of leakage.

 

[fisherman73]

Re: sx cobra rattle/vibration noise

Gear lube looks just like the day I changed it. does anyone have a copy of the previously mentioned bulletin?

 

[mikeneal]

Re: sx cobra rattle/vibration noise

Do a search here there was a guy a long time ago that had simular issue. I have a 99 SX drive and occaslly mine does the same thing. (rattle at idle) Always when it has been run and lube is thin and goes away when it goes in gear or revs go up. It started to made the noise when i bought the boat used at 50 hrs on it and now has over 400 hard hours and the same. Lots wake boarding in and out of gear and heavly loaded. Does not always do it and gear lube has always been changed at 50 hrs intervals, never has any dust and always looks new, but change it regually cause oil is cheap and outdrives are not. I think it is caused by slight backlash preload and the noise when thr idle is rough (mine is GL carb motor). Someone smater than me in the other post said it was slight mis adjustment of a shoe that moves the gear.

 

[fisherman73]

Re: sx cobra rattle/vibration noise

Thanks Mike I appreciate the info. Your explanation is consistant with the noise that I am getting. I also change my oil very frequently Hopefully it will never manifest itself into something serious but I guess it always pays to be proactive especially with boats!

 

[mikeneal]

Re: sx cobra rattle/vibration noise

Yea, I am pretty anal guy and it was touge for e to let it alone......nothing mechanical ever "fixes" itself.