470 mercruiser intermittent growl

[fishinmaniac1]

I have a 470, 4 barrel mercruiser. Have noticed an intermittent growl when idling. Once motor is warm, the growl disappears. Have taken it to three mechanics, who have heard the growl, but do not know what it is. Last one pulled the leg off and fired up the engine to ensure it wasn't something in the leg. Engine still made the growl and he didn't know what was causing it. He suggested pulling the engine out and checking the coupler. I don't want to spend the $$$ unless I know pulling the engine will get to the cause. Leg had new u joints, gimbal bearing, top end gears put in in July. I also took belt off and ran engine for a few seconds...noise still there.<br /><br />Any ideas on what would be causing the growl would be appreciated. Thanks

 

[Don S]

Re: 470 mercruiser intermittent growl

If you pull the outdive off, the coupler is doing nothing and couldn't make the noise.<br />I would suspect the alternator (if equipped) the stator/rotor if equipped, or the water pump.<br />None of which needs an engine pull.

 

[bigbrownbuku]

Re: 470 mercruiser intermittent growl

i saw a 470 this year with the same growl but never worked out what it was. the engine i serviced had the original pulley mounted charging system and water cooled block mounted regulator. i also eliminated the leg and water pump from my engine, not the stator however.<br />interested to know what it is.

 

[Stings]

Re: 470 mercruiser intermittent growl

the problem is, its a 470.

 

[vicsponjr]

Re: 470 mercruiser intermittent growl

My 488 makes the same noise I think. Sort of like something is rattling around. Almost sounds like something rattling around in the pan, or some detonation going on. I had a Buick with a 4 cylinder in it years ago. Would sometimes make a noise similar to the one I'm hearing. Someone told me it might have been a sloppy timing chain causing the timing to jump around.

 

[JPG44]

Re: 470 mercruiser intermittent growl

fishinmaniac1,<br />Inspect your distributor.I have a 470 now with the same noise, I can visible see my dist vibrating like hell.I haven't got it out yet to check it but that is were I'm looking.<br /><br />Jack

 

[vicsponjr]

Re: 470 mercruiser intermittent growl

Jack, be sure to let us know what you find. My distributor vibrates too, but no more than the rest of the engine, or anything withinn 50ft, lol.

 

[dug out]

Re: 470 mercruiser intermittent growl

Have the same problem. Noise only happens at start up and lasts for a few minutes. I have a Sea Ray 270 Sundancer with twins. My port engine did this last year. Had the gimbal bearings, boots and everything else that goes throught the transom replaced on both engines this spring. Still had the noise on the port engine. Now the noise has started on the starboard engine too. A marine mechanic that has over 25 years experience has no idea what the noise is. Thinks it might be related to the charging system (balancer & stator). The noise on mine isn't coming from the distibutor. I'm trouble shooting a distributor problem on the starboard engine. With the new distributor the noise is still there.<br /><br />Could it be bad gimbal bearings, even though they are new? How about motor alignment? Someone suggested the problem may be in the top gears of the outdrive and the noise is being echoed into the engine compartment. Had new U joints installed this spring and a new yoke on the port side.

 

[JPG44]

Re: 470 mercruiser intermittent growl

I wonder if we are all talking about the same noise? The noise Dug out has sounds like mine, evident at start up then goes away.This is my friends 25' Blackfin,and has twin inboard 470's, so we dont have gimbals and boots.This noise is a slow speed noise, it does not match the rpm of the engine.Both the engines have been replaced with Jasper's recently 03/04.It has to be something transfered and that rotates at a slower speed than the eng.Dist,oil pump,alt,raw water pump.Well see

 

[fishinmaniac1]

Re: 470 mercruiser intermittent growl

Took the boat to a very experienced mechanic last Thursday. Fired up the engine and the noise was gone. He kept the boat for 2 days and started it 6 times...no noise. Fired up the engine this am and noise not there! Is it possible the noise can simply disappear? Prior to last week, the intermittent growl was there every time the engine was fired up since mid July, but only at low rpm until the engine was warm.