Tapping Noise from 3.0L

AggieFX4

Recruit
Joined
Jun 11, 2003
Messages
5
Howdy, I just purchased a 1996 Sea Ray 175 RB that is 18'2" and is powered by a 3.0L Mercruiser I/O. I bought the boat from an "seemingly honest" individual with between 80 and 90 hours on the motor. Well, we took the boat out for a test run prior to buying and the first thing I noticed was a slight tapping noise coming from the engine at idle. The first thing I thought was the lifters, but he assured me that he had that checked out and the shop said that it wasn't the lifters that it was just normal engine noise. What else could the problem be and is this anything to worry about? He had just spent $375.00, the weekend before I bought the boat, on normal maintenance, carb replacment, and fluid changes and assured me that everything checked normal. Don't get me wrong, the boat runs and looks GREAT, however, I am just a little worried about the tapping noise. Any help would be appreciated.
 
D

DJ

Guest
Re: Tapping Noise from 3.0L

Aggie,<br /><br />If you can hear it run again, do this:<br /><br />Get a very long screwdriver and hold the handle end to one ear. CAREFULLY place the blade end on various engine components. You should be able to isolate the source of the noise. Don't forget to check in the area behind the engine known as the midsection.<br /><br />Tapping noises can be from components as simple as a nicked belt.
 

rogerwa

Commander
Joined
Nov 29, 2000
Messages
2,339
Re: Tapping Noise from 3.0L

I've also read on this board that the exhaust flapper can amke a chattering sound at idle. I have an 87 3.0 MC and have never heard mine, but I will say that these are the not the quietest of engines when running normal.
 

Pete30

Petty Officer 3rd Class
Joined
Apr 6, 2003
Messages
80
Re: Tapping Noise from 3.0L

I have an 87 3.0L OMC (same engine I believe) and it makes the same noise, its a rythmic knock knock knock at idle. At higher RPM's it disappears, and the engine purrs at WOT. I'm not an expert, but it would make sense that it is the exaust flappers, because they would be pushed open by the pressure at higher rpms. The noise from a lifter, it seems would get faster at higher RPMs.
 

tjkprop

Cadet
Joined
May 29, 2003
Messages
10
Re: Tapping Noise from 3.0L

I had this noise on my 88 Wellcraft. I had it checked when I purchased the boat in 00 and was told normal. I had it 3 seasons and ran it on the Ohio River 200 plus miles on weekends and never had a problem. Just traded it in last week and was gone over by dealer mechanics for trade in value and checked uot fine.
 
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