Knocking noise....from coupler area

[djhoosier]

Have a recently purchased Searay with 230MR mercruiser. It has a knock from the coupler area inside the boat while running with muffs in the driveway. To date I've replaced the ujoints, checked the upper gearbox gears for chipped teeth (none), checked and realigned gimbal bearing with a proper alignment shaft. The engine coupler splines feel and look OK (nice "fat" splines, not pointy). Regreased spline with the Mercruiser spline grease. Had started engine with drive off the boat and the noise was not there. Gimbal bearing is smooth.

I've still got that intermittent knocking, sounds like it's in the coupler area, but everything looks and feels OK. Any ideas? Frustration is really here...

 

[unreel]

Re: Knocking noise....from coupler area

Sounds to me like your exhaust shutters, I have two boats right now that have noiser than hell shutters on them. Sounds like lifter noise or bad coupler and or piston slapping. A metalic rattle shound. I am not shure quite what to do. I think alot of guys get pissed off and take their chances and pull them out all together. Grab ahold of your exhaust if it cold(don't burn yourself) and you can feel those things banging the sidewall of your y-pipe.

 

[hard-3]

Re: Knocking noise....from coupler area

check the drive plate on the engine. it might be cracked and allowing enough flex to knock. might have to use an inspection mirror and stand on your head to see it. i'm guessing it is a bravo drive from your description . how did the bushing in the transom plate look if this bushing is shot it will let the shaft flop around inside the housing . there is a grease fitting that lubes this bushing that gets overlooked . possible the bearings on the upper unit are loose and you have just enough wear everyplace to let it viberate or flop around. just guessing . good luck
Jeff

 

[Don S]

Re: Knocking noise....from coupler area

If you knocking sound is actually more of a tinny clicking sound, it may be the exhaust shutters in the top of the exhaust Y pipe. If the rubber coating burns or wears off, they will click loudly on the Y pipe.

 

[Fishermark]

Re: Knocking noise....from coupler area

Had started engine with drive off the boat and the noise was not there.

That would seem to eliminate the exhaust shutters.