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'98 4.3 v-6 4bbl engine knock

M

mike1970

Member
I finally got the engine running great. Tonight, I was tooling around the pond, everything running great, then the boat bogged down. Pulled it back to idle, and heard it knocking, 1 knock per rev. Shut it down, nothing leaking, smoking, etc.
I was a little way from the ramp, so I started it up and idled towards the ramp, still knocking, oil pressure still great, kicked it up a little (8-900rpm) so I could get back. A couple times it bogged and stalled. Started it back up, then the knock would get quieter, even disappearing for a second or two. Then when I got about 500 feet from the ramp, it disappeared altogether. I goosed it and it took right off, nice and smooth like nothing was wrong, then I got to the ream and shut it off and brought it home.
Is it possible for a rod knock to come and go? I am pretty sure it is a rod, but I have never heard of it doing this. Could I possibly get lucky and maybe it is something in the drive?
It is a '98 4.3 rwc 4bbl alpha.
Thanks.
 
Well, I think I got lucky. Started it up today, no noise. Let it run for almost an hour, just started to get a little knock/ rattle. Traced it to the outdrive. With the drive up as high as the trim limit will allow, I started to get the noise. Trimmed it down and it goes away. I assume it is the u-joints on the input shaft to the drive.
Does anyone know- can you replace just the u-joints? Does it need to be replaced as a assembly? Is it a DIY project, or are there special tools needed?
thanks
 
You'll actually be replacing the bearing crosses.
Check to make sure which bearing cross was used on your drive.
I'm thinking that the 1998 used the externally clipped bearing caps.


The A drive, I believe, will allow you to change bearing crosses w/out removing the drive shaft assembly from the upper unit.

MC-GENIIC.gif
 
Thank you for the replies. Where would you recommend is the best place to get them? The ones I looked at were in the $65-$170 range.

Thanks Mike
 
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