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Merc 470 making noise at high rpmbs

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aero3113

Contributing Member
I need help finding the source

I need help finding the source of the noise that is coming from my 470 at about 3200-3300 rpm (almost full power).it sounds like a tapping/crackiling sound.The sound is gone at anything below 3200 rpm's.Please help.THANKS.
 
Keith.
Not much to go by. Whe

Keith.
Not much to go by. Where is the noise coming from? Front middle or the back area of the engine?
 
its hard to tell I have to bri

its hard to tell I have to bring the boat out and have someone drive while I listen.I think it sounds like it is towards the middle to front area.would a fuel pump make noise if it is worn?
 
That sounds like it might be t

That sounds like it might be the exhaust shutters.was it at high rpms?Because I was thinking that that might my problem.Will it do any damage if I keep running with it if this is the problem?Thanks for the help.
 
If it is the shutters you stan

If it is the shutters you stand the chance of letting water back-up into the engine. Like coming off high throttle to zero and the wake could push water into the engine. Atleast that's what I've been told.
 
Do I have to pull the engine t

Do I have to pull the engine to replace these or can I do it with the engine installed?it is a 1983 470.
 
"It sounds like you have the o

"It sounds like you have the older style Y pipe and shutters so you will have to remove motor.
The newer style the shutters are just bellow the elbows and you can replace with out pulling motor, just the risers and elbows have to be removed."
 
"Paul's right. I have a 95

"Paul's right. I have a 95 Mercruiser 5.0 with the newer style so only had to pull the elbos. Good luck, hope that solves the clatter."
 
"I was able to remove the exha

"I was able to remove the exhaust elbows to reach the shutter.It was missing, just the shaft where the shutters are attached was there and I could not find the pieces anywhere. I even removed the drive.I guess the guy that hade the boat before me removed them when he had the drive off.Could a bad lifter be making this noise??its only at high rpm's (3200-3300) any lower rpm is fine."
 
"Keith,
When the noise happen

"Keith,
When the noise happens, is it running smooth or missing? Also, what are your gauges saying, volt/amp and oil pressure. If volts/amps are jumping, could be alternator/voltage regulator problem. I have heard that these engines sometimes lose oiling to the top end. You may also want to pull your distributor cap and have a look inside. Just a few suggestions. Let us know what you find. I've got two of those mills in a'77 SeaRay 240 SunDancer. Good luck}
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"all the gauges read normal ,I

"all the gauges read normal ,I will pay better attention to the volts next time.I lubed the u- joints on the drive and re-did the timing I will let you guys know what happens this weekend."
 
"Guys, thanks for your help th

"Guys, thanks for your help the noise is gone!!!When I re-set the timing I pulled the distributor and rotated it about half way and for some strange reason the noise is gone.Runs like new.Thanks again."
 
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