Black Dust By Motor Mount

[KenKrawford]

After finishing an oil change yesterday I noticed some black dust by the starboard aft motor mount. The first image is looking aft on the starboard side of the engine. The second one is looking down from the engine access in the aft cabin.
About the only thing near there is the throttle and decompression cables but it can’t feel any wear on them and they are inboard from where the powder is accumulating.
Any ideas?

IMG_1509.jpg (185.75 KiB) Viewed 5327 times

[wolfe10]

Ken,

Normal sources of that kind of "rubber dust" are belts (a long way from where you see the dust if I am correctly identifying the location) and the engine mount itself.

Both are rubber and could cause what you see.

Hard to tell from the picture, but verify that the large nut at the top of the mount is tight. If not, it could allow excessive vibration that could contribute to breakdown of the rubber mount.

You can also pull/pry to see if the mount has failed.

[JerryRoss]

When I had black dust in the starboard aft engine area, it was due to a failing damper plate. The dust was coming out an inspection or timing hole in the bell housing starboard side. You can check by putting tape over the hole, cleaning the old dust, and seeing if you get new dust. If not, good chance it is the damper plate. Final check would be to remove the tape and see if you get new dust. I'm not sure how long to run the engine with the tape on and off but I would guess several hours should do the trick. I posted my experience and pictures of the old damper plate several years ago.
Good luck.

[KenKrawford]

Brett & Jerry, thank so much for your input. I never thought of engine mounts or transmission as a source of the dust. I'll definitely check them out.

Jerry's post (shown 5 threads down from this one) titled "Damper Replacement" is fantastic. There are many high quality images and lots of text to walk you through the process although I'm hoping I won't be needing it!

[sargentef]

In the Boat US magazine (Oct/Nov 2018, issue), beginning on page 77, there is a troubleshooting flow chart about engine vibrations. The flow chart begins with (worn engine mounts) and the rubber residue next to a engine mount.

So have you noticed any additional vibrations?

Seawing
Hull# 309

[digitalvillager]

Just changed the zinc in the HE yesterday and both cables are always up against the zinc nut. I check each time I change the zinc expecting to find grindings as in your photo, but nothing yet. Check again, I bet you will find the nut has been working the cable. Also, check just forward and aft of the nut as the cable shifts slightly when put in gear.Could also be that shifting is pushing the cable along a sharp edge of the nut.

[KenKrawford]

It turns out the motor mount nut was the culprit. I could turn it using my fingers. I didn't have a 15/16" socket on board so that will another project for the next trip.

[wolfe10]

Ken,

Once tightened down, pull HARD side to side to see if the mount has failed. All that dust could indicate a separation of the metal to rubber bond from the excessive vibration.

Since the engine has likely been moving around, particularly at idle speeds, probably a good idea to check shaft alignment.

Also, a good idea annually to check torque on the mount to stringer bolts.

Brett

[KenKrawford]

Thanks Brett. Will do.

[sargentef]

Ken, I was just down in engine compartment looking engine over after an 8hr motor into the wind and 3 knots of tide, and noticed some black powder dust near one of my rear engine mounts. Did you ever resolve your dust issues?

We put a Gori 3 blade prop on the boat this spring, and have noticed a vibration we never had before!
"Seawing"
Hull# 309 05'

PS, The gori prop has been the best equipment update we have ever made, we can now achieve hull speed in over drive!

[KenKrawford]

I found the top bolt on the starboard aft motor mount could be turned with just my fingers. I tightened it down and all seems fine. I didn’t notice any vibration while motoring after tightening so decided that I wouldn’t mess with checking engine alignment.

[sargentef]

I was able to get 3/4's of a turn on my engine mount bolt and all seems well!
"Seawing"
Hull# 309 2005