New 4.3L Mercruiser

[SeanDavis42]

Rebuilt 4.3L V6 Mercruiser w/ new 4 brl and intake, FW cooling, and new exhaust flappers. Noticable tapping at idle. I have not had the boat in the water since the new motor went in just running it with the muffs and hose. Any ideas

 

[Flysfloatsor]

Re: New 4.3L Mercruiser

Check the rocker arms. My first guess would be one has too much lash.

 

[paultjohnson]

Re: New 4.3L Mercruiser

Are you sure its an engine tap? At idle those exhaust flappers opening and closing can sound like a tap... does it go away if you bump the RPMs up a bit.... Got a stethoscope ?... I use the corrugated hose from my wet/dry vac as a stethoscope. Works great... for locating the source of those sounds

 

[james67]

Re: New 4.3L Mercruiser

mine does samething never thought about exhaust flaper, i even thought it might be the coupler.

 

[fastimz]

Re: New 4.3L Mercruiser

My 454 does this and it is the flappers. It is probably the same with you. Rockers shouldn't have any lash unless you have a racing 4.3 with a solid cam. kidding!

 

[Flysfloatsor]

Re: New 4.3L Mercruiser

Check the rocker arms. My first guess would be one has too much lash.

Oops, as in not set correctly during the rebuild. should be at zero lash, 180 Degree preload for hyd lifters.