Turn the key off...get a strange sound.

Ezgoin

So I'm working through the list of problems encountered with this  2005 496 Mag 262 Captiva and wonder what might be causing this issue:
When I turn the ignition key from On to Off...weather the engine is started or not, I hear this loud kinda grinding sound as if something is disengaging at the engine.  It dosn't sound like anything that was designed to make a noise like that.  Is there something with the starter that engages/disengages when the key is truned from On to Off and back?  

Cableguy Greg

It is probably the trim tabs auto retracting. I get the same sound on my boat when I turn the key off.

Ezgoin

Never thought of that possibility, but the trim tabs are always up all the way when the boat is on the trailer since the trailer bunks actually protrude beyond the transom about 5" directly under the trim tabs. I know, not great but that's how it came. Do you think they would still make the noise?

Cableguy Greg

No matter what position they are in, they will make a noise when you turn the ignition off.

Ezgoin

Hopefully that's where it's comming from! Much better than what I was fearing!!

Dream_Inn

I'm betting it's your fuel being pumped out.  I get the vvrrrmm every time I turn mine off, definitely not trim tabs.

MarkB

Is it high pitch sound or a grinding sound?

TikiHut2

Fuel pump is my guess too.

Ezgoin

It's more of a grind/growl sound.  Happens every time I turn the key from On to OFF.  I hear the fuel pump spool up when I turn the key on, but only the grinding sound like something mechanical is moving when I turn the key Off.

TikiHut2

Now I'm curious. Maybe I'll check mine out tonight to see what causes my usual key-on and key-off sound.

Dream_Inn

I'm betting it is the same thing mine does as well.  Definitely not trim tabs.  You could have someone in the back watch your tabs when you do it.

My turn key on sound is different, it's the pump pressurizing.  The turn off is what I believe is something removing that pressure?

212rowboat

Put your hand on your fuel cool unit and hit the breaker. 

MarkB

The normal trim tabs sound is a medium pitch, no grinding. If something is jamming the trim tabs, maybe a different sound, but not sure, as it's hydraulic, so really the fluid should simply go through the pressure relief valve.

Ezgoin

As I mentioned, the trailer bunks protrude past the transom a few inches right under the trim tabs so if they are trying to move they can't. I guess I should pay more attention to if it makes the same sound when it's in the water rather than on the trailer. Why would the tabs need to cycle when the ignition is turned off?

Ezgoin

What is the fuel cool unit?

MarkB

The trim tabs will want to push up when you shut off the engine, not down toward the bunks.

raybo3

I had the same problem. It ended up being a bad relay. My fuel pump would not shut off after shutting the engine off. 

Ezgoin

This is definitely not a fuel pump noise.  Its quite loud and sounds like somthing mechanical moving in a non-lubricated environment.  The trim tabs are in a full up position and couldn't cycle up or down even if they wanted to because of the trailer bunks under them.  Guess I'll know when it breaks...whatever it is!

212rowboat

the fuel cool unit is on the starboard side of the block, near the accessory drive area.  it does as it sounds, and cools fuel.. but.. it's also a clever way around a USCG requirement of 'no fuel return' on gas engines.  it collects a supply of fuel from the tank, maintains pressure in that supply, and sends it to the rails, and only resupplies fuel as needed- hence, no return to tank.  pretty clever, but not much different than mopar uses on many of their EFI vehicles- less the cooler unit.. they rely solely on the pump maintaining a certain prescribed pressure (49psi +/- 4psi).  

after re-reading your thread here, I'd lean away from fuel issues right now.  I'd look more toward greasing your gimbel and/or the shaft and joint leading to the bend, and seeing if that eliminates or reduces your noise.  i'd also listen real close to hear if it is happening while the engine is running, but is drowned out by the engine noise.  this noise would originate from directly behind the engine.  

just my thoughts. 

Cableguy Greg

Ezgoin said:

As I mentioned, the trailer bunks protrude past the transom a few inches right under the trim tabs so if they are trying to move they can't. I guess I should pay more attention to if it makes the same sound when it's in the water rather than on the trailer. Why would the tabs need to cycle when the ignition is turned off?

The tabs automatically retract to the up position when the ignition key goes from the run position to the off position. Maybe it is just my setup with Lenco tabs, but they cycle to the up position when the key is shut off. It was just a thought when I mentioned it and the sound that you are describing is very similar to what my tabs sound like when I shut the key off, whether the engine is running or not.

Robyw1

My Lenco tabs do this. It does it longer when the tabs are down when I turn off the ignition. Even if they are already up it will do this for a second. 

Ezgoin

Hummm... I also have the Lenco tabs.  So even if the tabs are already in their full up position you will get the cycling noise when you turn the key off, even if the engine was not running?  The noise only happens when I turn the key from the On position to the Off position and it happens every time I do that.  I do not hear the same noise when going from Off to ON.

Ezgoin

212rowboat, I'm sure it's not a fuel pump or fuel system issue.  Not that kind of sound.  The Gimbal shaft/joint issue might be something to consider, but not sure why there would be movement there by simply turing the key on and off.

212rowboat

Oh..... It doesn't do it just after the engine dies, but still with the key on/off whether you start engine or not...I lack reading skills, apparently.

Ezgoin

Nope. Just sitting on the trailer I can turn the key to the On position ( no engine start) then turn the key to the Off position. As soon as I turn the key to Off, I get this loud growling noise as if something heavy and mechanical is moving from one position to another near the rear of the engine. Lasts about 1 second and Happens every time on the trailer, but I haven't paid attention to if it happens in the water, but I think it does.

Robs_232

Lenco tabs auto retract feature. Mine do it every time with ignition from on to off.

JoeStang

Yep, sounds like tabs to me also. Mine make the retracting sound regardless if I had them deployed or not. Out of the water they're probably even louder.

MarkB

Could be the lenco hydraulic drive.

Ezgoin

Yep, you are correct.  It's the Lenco tabs doing their thing.  Never had Lenco tabs before and didn't realize they cycled like that.  Kind of an ugly sound they make.  Thanks for the input!

Cableguy Greg

Glad that mystery is solved!!!

Ezgoin

That's one!!

Unfortuantely, this boat came with a whole bunch!!  I did discover Saturday that the reason no sink water was discharging from the discharge port was becuase the drain hose ended 4" before it connected to the drain port nipple!  Subwoofer wasn't happy to have the sink discharging on top of it!  I'd like 30 minutes in a room with the previous owner of this boat!