40HP rapping noise

[Ponchojuan]

I have a metallic rapping noise comming from the engine. Most noticable at medium rpm or decelleration.<br /><br />Any ideas on Diagnosing?<br /><br />Runs ok. Idle a little weak. Stalls occasionally. Runs well other than that.<br /><br />poncho

 

[R.Johnson]

Re: 40HP rapping noise

I just recently had a 40 doing just that, after much searching, the owner told me he smacked a log with it. It was a pinion gear breaking up.

 

[Ponchojuan]

Re: 40HP rapping noise

Just started it up here at home. Noise is consistent at low rpm too. Popped the plugs and tested for wrist pin and rod play. Could not detect any. Pistons look relatively clean from the plug holes. Sound seems to becoming from the powerhead, but I suppose it could be the pinion. Tried shifing the engine into reverse and forward while at idle. Nosie remain pretty consistant.

 

[Ponchojuan]

Re: 40HP rapping noise

Originally posted by R.Johnson:<br /> I just recently had a 40 doing just that, after much searching, the owner told me he smacked a log with it. It was a pinion gear breaking up.

I fired up the engine and listened with a stethoscope. Boy, it's tough to track down the source of the rapping. I can hear some piston slap, but it could be coming up from the pinion gear too. <br /><br />Is there anyway to check if it is the pinion gear? I would hate to teardown the top when the problem is in the bottom.<br /><br />poncho

 

[itstippy]

Re: 40HP rapping noise

Take the lower unit off. Duct tape a garden hose to the water inlet tube to supply water to the powerhead. Run the powerhead at low RPM and listen. LOW RPM!

 

[swimmin' for shore]

Re: 40HP rapping noise

I'm really new to this, and don't want to sound crazy, but I had a similar noise in mine. Flywheel cover...the nut came loose, pot metal cracked, and a piece popped down into the flywheel. Caused rapping as the wheel turned. Sounded pretty bad, but didn't decrease RPM's or performance.

 

[Ponchojuan]

Re: 40HP rapping noise

Thanks for the tips, but the compression trst told all. Lower cylinder is shot. This is not good since this also drives the VRO. Time for a rebuild. I've done a numner of auto engines but never a powerhead.<br /><br />I will start another thread after reading the service manual.<br /><br />Thanks for the help guys.