350 GM has a bongo drum player inside at 1900rpm ?

[loadnet]

1986 Wellcraft 23 Foot<br />Engine: GM 350 CUBE 260hp <br />Drive: MERCRUISER ALPHA 1<br /><br />Engine idles nice and quiet all day long, but bring it up just a bit say 1900 to 2100 and an erratic internal knocking sound starts.<br /><br />It's not a steady knock like a rist pin or bad rod bearing.. and it doesn't even do it everytime ya bring the rpm up... but 2 out of 4 times slowly bringing it up from idle the noise will occur.<br /><br />Almost sounds like a bent push rod or fuel pump lever/pin acting up once the RPMs start to climb..<br /><br />Weird tubular type erratic tap/knocking sound? and has no particular rhythem to it..<br /><br />Kinda sounds like there's someone in the engine playing the bongo drums for a split second.<br /><br />Took off the valve covers and all of the rockers look good.. none sloppy.<br /><br />Haven't adjusted them yet but heading in that direction next..<br /><br />Anyone have any thoughts on this before we end up tearing it down?<br /><br />Thanks in advance..<br />PB customerservice@401hosting.com

 

[Wellcraft 89]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

Before you rip into that engine ,be sure your sound is not traveling from the u-joints to the engine compartment.<br />Take the drive out and chk them and the gimble bearing. <br />Could even be the coupler getting ready to blow!<br /><br />Just my $.02<br />Rich

 

[loadnet]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

The noise is happening with the unit out of the water..in neutral, prop not turning... so I'm thinking the joints and gimbal should be ok, right?<br /><br />What coupler are you speaking of? the prop coupler?<br /><br />Thanks for the getback..

 

[ufm82]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

Capt.<br /> The driveshaft and U-joint turn all the time, no matter what the prop is doing. The shaft is directly coupled to the engine- you only disengage the lower unit. <br /><br /> You may have an issue there- it would be a good place to look before going into an engine. <br /><br /> Now, if it IS in the engine, is the noise hollow or thudding? I am thinking piston slap. Maybe a skirt sloppy in a bore.<br /><br /> Ever hear a newer F150 start up cold? Same sound?<br /><br /> Worse cold or hot?<br /><br />UFM82

 

[akriverrat]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

just a wag, but could it be exhaust flappers?

 

[loadnet]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

Thanks for telling me about the drive moving all the time.. don't know what I was thinking there.. sorry.<br /><br />YES.... the noise is a hollow sounding erratic rap.. like when it raps it's like all over the place.<br /><br />like hitting bongo drums with a 'stick' rather than your hands or forehead.<br /><br />The noise IS kinda near the rear of the engine, like around the bell housing however we're doing another compression test today, and going to adjust the rockers using a set of valve covers that have been cut out so as not to leak oil all over the joint..<br /><br />Once we find this goofy noise I'll let everyone know what it is..

 

[loadnet]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

UF.... what's the procedure to check the coupler?

 

[Bondo]

Re: 350 GM has a bongo drum player inside at 1900rpm ?

When you pull the outdrive, it's the Splined hole(the Smooth hole is the gimbal bearing) that's left.... Test,+ Inspect from there....<br /><br />I'm thinking Loose U-joints.....