Strange high pitch whine...500Efi ???
 

great day boating but.....

Strange High pitch whine (sounds like an alarm buzzer just not as constant, still it's very piercing) out of port engine 500 efi (50 hrs). No power loss all fluids ok- runs 110mph easily with no problems. Here's the weird thing.... Goes away in reverse and idle forward. Neutral starts again. bring it up on plane starts again. When I turn the engine off it takes a second and a half to die out. Brand new drives so no issues with equipment. plus it's coming frome somwhere around the engine. It's so high pitch your ears won't let you isolate it.

Any Ideas?

Last week I sucked a little grass up but no big deal. flushed oil coolers with no hiccups.


Thanks for your help.

Maximus

Must be the hidden supercharger.

Accccchem!!!!
 

I wish!
Maxximus

Did ya check for a potato in the tailpipe?

Gimble bearing???

It means it's about to puke and you should trade it even with me for a SBC.:D

Seriously, my first supect in all high pitch whines is a vacumn leak, but it wouldn't go away by changing gears.

I had a 96 Scarab with t/500 HP's and had a similar high pitch
whine. I do not recall if it was a pulley for the belts out of a line or a bad belt. Look at the belts and alinement or a belt too tight.
One or the other fixed our problem.
Doug

continues for a little after shutoff??

Fuel pressure regulator on the fuel rails???

Does it whine louder with more RPMS?

Mine sounded like I was running a blower engine.

If it has XR Bravo's and not XZ Bravo's it's the drive due to the way the gear is a straight cut in the XR vs. a bevel or angle cut gear in the XZ or Bravo 1.

I remember it in the 38 Cig thought I was going to launch all the engine guts out of the top of the engine hatch.

hmmmmmm
 

Now I'm really confused?

Belt seems fine but I'll replace it. Vacuum line between plenum and fuel pump (clear) is collapsed while running. I removed from both ends and does not alleviate the sound. Still it is collapsed could it have dammaged the fuel pump?. Drives are new XR's with Two inch Shorty Sportmaster lowers (drive oil fine and 2hrs old ) did not make the sound first day back out. Gimbles are in perfect working order.

Andy ..checked for potato.......nothing. However I did find that check I owe you for my new security system......I think I'll keep it!
:D

The noise rises slightly while spinning up, but is it very slight.


Thanks for all your help guys.


Maximus

line from mechanical pump is to keep fuel contained in the case of a diaphragm rupture. If the hose is routed to a vacuum source, it will indeed collapse. My lines (carb motors) are routed above the throttle plates (not a vacuum source). Wouldn't think your hoses are an issue.

You mentioned the noise takes a couple of seconds to go away at shutoff. If the noise continues after all rotation has stopped, then it will not turn out to be gear noise, or any other driveline noise. Belt noise can continue until the rotation is completely stopped, but not afterwards.

You have a high pressure regulator on the fuel rail(s) that bypasses fuel back to the high pressure pump. Get a stethescope and rule out that puppy before you start spending money.

m

Makes the most sense
 

Mcolliston -
It is not a mechanical sound. And your hypothisis seems to make the most sense.

I'll give it a shot , however I'm not looking forward to sticking a stethscope up to that sound.

Maximus

High pitched whine?
 

Was the wife/girlfriend on board at the time? :D :D :p :p

hahahahahaha
 

That's what I need humor!!!!! I just picked up two Brand new Water pump Kits and a belt ....grabbing my wrenches and going to work....

Maximus

Fixed!!!!!
 

Stethascope thing worked ! The reason I couldn't place the sound was it was centered under the plenum. Some type of PCV valve/vacuum thing w / an AC Delco part # CV-856-C Valve was whistling so friggin loud!!!

Is it worth calling warranty over or will NAPA have it for 1.99

Maximus

Ouch, dont you hate spending money on things you dont need.

I have cleaned mine before and free'd them up until I could get another. Just a suggestion.

Congrats, I would have bet money it was the gear whine from the XR's but cool.

Go to a GM dealer and buy a quality part. You get what you pay for at the parts warehouses.:rolleyes:

Yay!

Your local Mercruiser man might have only charged you $26.95 for it after replacing half of the nonwarranteed electronic doodads first (also on your dime).

Hmmmmm, like I said, high pitch whine=vacumn leak most of the time.:)

Thanks for all your help
 

Cuda- you were right! Thanks again for everyones help in trying to solve this "Merc Mystery" .

Maxximus