View Full Version : Boomerang Knock

07-25-2005, 01:44 PM
My '97 Boomerang seems to have a very annoying knock/rattle at idle. It appears to be coming from the area around the back of the engine. (It is nothing coming from the actual engine) It is a very constant thud,thud, thud. It stops as soon as the transmission is engaged. Anyone out there had any problem like this? It is driving me nuts so ANY type of help is more than welcomed.

07-25-2005, 08:48 PM
I had the same problem once. I would bet good money that the locking nuts on your engine mounts are loose.


07-27-2005, 10:33 AM
I checked the motor mounts. They didn't appear loose. It may be the passenger side exhuast tapping the hull. The search continues.

Brian Raymond
07-27-2005, 11:07 PM
When the engine idle is low (550-650rpms) it can cause the tranny pump on the front of the trans. to knock. In most instances, just a slight idle increase will deter this knock. I would not take the idle, in neut. past 750-800rpms. Your idle, in gear, should be 700-800rpms. This can also be smoothed out by adjusting the idle air bleed screws located on the sides of the main metering block on the primary side. This can be done when the boat is in neut., slowly turn each screw out until your idle drops off, then, turn them back in slowly, you will hear a point in the motor where it will increase in rpms. When turning them in, and the motor srarts to drop rpms, back the screw out until the max. rpm. Do this on both sides. Hope this helps. Brian Raymond

07-29-2005, 02:58 PM
Thanks BR. I'll give that a try.

08-15-2005, 02:40 PM
The knock has not stopped even after checking out the idle. By increasing the idle all I did was make the knock faster. I have done and checked everthing I know. The sound is not noticable when sitting in the rear (presumably because of the exhaust sound drowning it out). Any other suggestions?