1988 3.0 bad knock - see video

[pmtom1]

Dad got this boat about 2 months ago. SPOTLESS (looks like brand new inside and out) 1988 Sting Ray 17.5. PO said 190 hours and it looks like it. Anyways... he has put about 15 easy river hours on and noticed a knock getting worse. Notice the wobble on the lower pulley. Pulled spark plug wires off one at a time and knock did not change.

We know this is bad. So if we go with a new / rebuilt long block, looks like about $2500-$3000 and we can use any of them but being pre 1990 may have to swap or buy a few parts. (coupler, flywheel). Does this sound right?

Or ripping it down and rebuilding whole thing. Definitely not afraid of that option, just not sure how much we would save. Id love some opinions on what could the max cost be for us to rebuild.

thanks for the advice!

https://photos.app.goo.gl/t1P5QNHRPn2SjXjL6

 

[bman440440]

I'm in no way a 3.0 guru... but my 1st thought is that you might just have harmonic balancer coming apart... you might be able to change that out and be good to go... I'm sure those with more experience/knowledge will chime in and get you going in the proper direction... and BTW the engine is CLEAN!!!!

 

[alldodge]

Sounds are a bit different when recorded on a phone, and ithe noise is not good, but for me not quite a knock. Bman might be right that its the harmonic balancer the way its wobbling around. Take the oil filter off and cut it open to see what is found inside

 

[TurtleTamer]

Almost sounds like top-end noise, but I agree with it probably being the balancer. If the crank were damaged enough to cause that wobble I'm pretty sure there would be nothing left of the oil seal and you'd have much more apparent problems than noise.

 

[pmtom1]

Thanks all....

Not sure if this changes anything but...yesterday put some Lucas oil treatment in. This morning it started up quite for about 10 minutes then came back full bore.

 

[Grub54891]

Ok, my 2cents.....A bandaid in a can is not going to fix the pully. Either repair the pully, or have a competent mechanic do it for you. If you keep running it as is, it'll cost you more than any treatment ever will.

 

[scoflaw]

I don't hear any knocking, Fix your pully

 

[pmtom1]

Agree Grub.... parked yesterday and we pulled her this morning with the intention of a complete teardown. Definitely not running it that way. After all these posts, we will check pully / harmonic balancer for sure and keep fingers crossed!

 

[Grub54891]

Good. Start with the pully, You can run it bolted to a pallet, supplied with water. If it still knocks after the pully repair, you keep looking.....