Grinding sound in forward at very low idle

[dvd]

Whenever I put the boat in forward at its lowest idle it makes a kind of grinding noise. It has pretty much always done this and if you give it just the smallest amount of throttle it goes away. I have just ignored it but I was out for the Wednesday night beer cans last night and a friend of mine was driving the boat and he commented on it. I have a pretty low idle but no tach so I can't tell you what RPM. Since it is only a this very low idle setting that it occurs I have not really worried about.

Anybody else have anything like this.

DVD

[Ball Racing]

Mine on ocassion after a little run, will a weird rumble stumble groan grind sound at a low idle and makes you think you just got something in the wheel.

I have not found what causes it yet, and you can go for weeks and not hear it, then it will do it every other trip, then go away.
It has always gone away when the rpms were increased.
Mine has done in gear and out of gear.

[Dave Neptune]

Perhaps

Try listenng at the accy drive. They can rumble a bit if the bearing is getting worn. Use a stethescope or put your ear to a screwdriver. I've heard some odd growls from them in the past, perhaps worth a listen.

Dave Neptune

[Ball Racing]

Mine made the noise with a fresh rebuilt acc. drive, as well as a older one.
I do have play in my idler gear.

[sastanley]

I have a little grinding too, and I am with Dave..I think mine's the accessory drive. I have not pulled mine, and I suspect it is original. Once your throttle her up a little bit, the engine noise takes over and drowns it out. I also get a little mechanical tick in hear at low speed too...I figure it is valves making noise on the lifters (is that what you call them on these motors?? I am really an OHC guy and used to rocker arms & tappetts & timing belts & stuff).

Since the rest of the motor seems to be in pretty good shape, that may be the item I rebuild this winter...and I'll do the little oil channel modification too.

[Ball Racing]

The sound mine makes can come and go, and sounds pretty deep.
It is not the sound I imagine a drive making, almost as deep as if something just gets tangled up in the crank or around the reverse gear.
It will just show up, and you can feel it when it happens.

[JOHN COOKSON]

I've never tried this so don't know how well it works but will pass it on anyway.

When the noise is happening press on the accessory drive pulley with a piece of wood (CAREFULLY!)
If the noise changes it means the accessory drive is making the noise.

TRUE GRIT

[dvd]

My noise is only at the lowest idle possible in forward gear. It seems to be emanating from the drive shaft area. Maybe I can post a video with sound to help.

dvd

[idreamOfSailing]

What do I need to know?

Coming in a tad late to this thread, but hopefully will get a reply. I'm looking at changing the Accessory Drive as I too am hearing a loud grinding sound in neutral or at low RPM in forward. What do I need to know when removing the Accessory drive? Once unbolted, does it simply slide out and the new one back in, and what do I need to take note of in terms of the distributor setting? I have an electronic distributor, so does it even matter? Thanks all.

[vtbob]

it seems that I have the same noise that your engine has. Don moyer recommended that I slowly move the shifting lever from reverse to forward to see if the noise started when the throw out bearing was engaged. I didn't hear the noise until the fingers were in the detent. The noise happens more often when going from reverse to forward but it happens just going into forward. it stops whether I increase the throttle or leave it in idle.it sounds like gears meshing or just touching.

[vtbob]

I'm not sure what else to check. I thought about trying to adjust the forward adjusting collar but ide just be going on a Easter egg hunt hoping for something good to happen.

[idreamOfSailing]

I have tried to replicate the noise while tied at the slip but cannot succeed in making it happen. It seems it only appears when underway. At this point I don't really know what the cause is, but my main concern is whether I would experience a catastrophic failure if continuing to use the engine with this errant noise.

[JOHN COOKSON]

I have tried to replicate the noise while tied at the slip but cannot succeed in making it happen. It seems it only appears when underway. At this point I don't really know what the cause is, but my main concern is whether I would experience a catastrophic failure if continuing to use the engine with this errant noise.

Try pushing on the accessory drive pulley with a piece of wood while the noise is happening. Any change in the noise implicates the accessory drive. Careful around moving machinery.
Have you checked the alternator and drive belt? Remove the belt and motor around and see if the noise goes away.
I had this sort of noise once and I was sure it was the accessory drive. It turned out to be that the stuffing box packing nut was a bit tight.

TRUE GRIT

[idreamOfSailing]

Interesting. Is that a serious issue having the nut too tight on the stuffing box, or is it just an inconvenience?

[roadnsky]

Is that a serious issue having the nut too tight on the stuffing box, or is it just an inconvenience?

It COULD be a very serious issue.
Correctly re-packing and Adjusting the stuffing box is an important item on your vessel.
Poor attention to it could score your prop shaft or even sink your boat.

Attached is a short article by Don Casey about it.
Let us know if you'd like more info...