1991 3.0 noise @ low rmp

[dshelly]

The noise sounds a box fan when the blade hits the side once in a while.It is coming from the rear of the motor.(1991 mercruiser 3.0)

 

[harveje]

Re: 1991 3.0 noise @ low rmp

My '90 Caravelle 3.0 has about the same noise about 3K rpms then goes away, it sounds tinny, like the thin metal flywheel cover on a vehicle vibrating

 

[dshelly]

Re: 1991 3.0 noise @ low rmp

Thats the sound, now what is it?

 

[harveje]

Re: 1991 3.0 noise @ low rmp

?ell if I know I can't find it. I'm scared to get in there while the boats in motion and don't want to run it that fast with the muffs on. Maybe some one else has had and fixed this.

 

[lilmandavis]

Re: 1991 3.0 noise @ low rmp

c'mon its just some belts and pulleys down there!! its not like your diving into a 672 detroit engine box with a 4ft fan rotating next to your ear!!! goin to have to get down and listen exactly where its coming from.

 

[harveje]

Re: 1991 3.0 noise @ low rmp

It's not that it's my wife will have to drive that bothers me...... It's hard to get the engine cover completly out of the way so I can get back there..

 

[dshelly]

Re: 1991 3.0 noise @ low rmp

It's coming from the rear, no belts or pulleys back there.

 

[Don S]

Re: 1991 3.0 noise @ low rmp

Just because something is difficult to do, doesn't mean it doesn't need to be done to find the problem, but, if the sound you guys are hearing is tinny and intermittent, it may very well be the cover on the bottom of the flywheel housing (Item 9 in the picture below)<br />If the screws (items 11) are loose or missing or the gasket (#10) is missing, that cover will make lots of noise.<br />And since it is so hard to describe sounds in a thread like this, it may also be the ujoints making noise. When was the last time you guys pulled your outdrives and inspected the ujoints and gimbal bearings?<br /><br />

 

[harveje]

Re: 1991 3.0 noise @ low rmp

I will look tonight to see if the cover is loose, I did not know they had one. That is exactly what mine sounds like. A real thin metallic vibration @ 2900 - 3100 PRMs then goes away. <br />Thanks for the pictorial Don.

 

[harveje]

Re: 1991 3.0 noise @ low rmp

My cover had the 3 bottom bolts missing, but the others were tight. I added 2 that I found, ran the boat 6-21 and a small vibe was still there but not like before. It takes some twisting but check, tighten and or replace these bolts to see if it stops your rattle.<br />Thanks Don