knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

[snowman51789]

i have a 92 thompson with a 3.0LX and a alpha one gen 2. my boat was running just good, but i wanted to check and make sure the gimble bearing was still good. i took it apart checked it (bearing still has life in it, but i will replace over the winter). when i put it back togather i was having some problems, the out drive would not push all the way in. there was still about a 1/16 or so of a gap between the outdrive and the houseing, i pulled it off, everything looked good, i reinstalled and the gap was still there so i decided to just tighten down the nuts. it did pushin the rest of the way. but when i start it now it makes a knocking sound, its some what faint but it shound almost like someone nocking on wood real fast. if goas for a couple seconds the goas away for a couple seconds and so on. its coming from the houseing it sounds like. im sure its not the motor. when you rev the motor it i think it might go away, but it could just be getting drowned out by the sound of the motor.

any help would be great

thanks

 

[meesh]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

You need to pull it back off and check your engine alignment. You need the proper tool and you can find them pretty cheap on Ebay.

 

[Bt Doctur]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

More likely the gimbal bearing is not fully seated. exactly how did you remove and re-install it?

 

[snowman51789]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

i removed and reinstalled the outdrive, not the gimble bearing. i left the bearing in bc it felt find (if thats what you meant). but if you meant the outdrive. i just unbolted it and pulled it out. put the new gaskets in and rebolted it.

as for the engine alighnment. i see your point but how would removeing and installing the outdrive affect it?? because it was fine before

thanks

 

[Bt Doctur]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

1/16th is normal, pushed on by hand. knocking can be caused by a bad gimbal bearing, a gimbal bearing not fully seated, loose U joints , chipped gear teeth.

 

[meesh]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

i removed and reinstalled the outdrive, not the gimble bearing. i left the bearing in bc it felt find (if thats what you meant). but if you meant the outdrive. i just unbolted it and pulled it out. put the new gaskets in and rebolted it.

as for the engine alighnment. i see your point but how would removeing and installing the outdrive affect it?? because it was fine before

thanks

Pulling it off really should not affect it if it was fine before. Problem is you have an issue that needs to be dianosed and thats the most obvious place to start.

 

[dubs283]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

1/16th is normal, pushed on by hand. knocking can be caused by a bad gimbal bearing, a gimbal bearing not fully seated, loose U joints , chipped gear teeth.

+ flattened o-rings on the driveshaft

hopefully you installed the drive with a complete drive gasket/o-ring kit??

 

[snowman51789]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

i forgot to mention the outdrive is practicaly new. i boutght it new last july. it has 20hrs at most on it. (if that matters)

however when i pulled the outdrive off i had a new gasket kit but did not change the seals on the shaft. they looked good. could i have put a flat spot on them when i installed it??

thanks for all the suggestions. they are all helping. i am mechanicaly inclided with almost all powersports but im new to boats. you guys are helping alot.

 

[Bondo]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

i am mechanicaly inclided with almost all powersports but im new to boats.

Ayuh,... Then you should know that o-rings are Never reused...

 

[snowman51789]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

Ayuh,... Then you should know that o-rings are Never reused...

Correction, SHOULD never be reused. i have done it at least a half dozen times with oils seals in the transmission and low end of the motor in dirt bikes when i was in a bind and didn?t have access to new ones. o-rings are actually very reusable. however that is in dirt bikes snowmobiles and atv's. i assumed since i have gotten away with that in those applications i would be ok this time. Like i said, im experienced in motor sports but im new to boats. just because i made a miss judgment or mistake doesn?t mean ive never picked up a wrench before.

 

[dubs283]

Re: knockin sound at idle. HELP!!!!!!!!!!!!!!!!!!!

just because i made a miss judgment or mistake doesn?t mean ive never picked up a wrench before.

nobody is questioning you abilities about being mechanically inclined

it is possible you broke one or both of the o-rings when installing

mercruiser recommends replcaing all the o-rings and gaskets when installing a drive

it is also recommened to apply oil or light grease to the o-rings to aid in installation (prevents binding and possible breakage of the o-rings)