Loud Knock - Thump Noise

[stevecti]

Hi all,

I have an SE106 I purchased in 8/09. It's on a wellcraft sportsman248 with a merc 5.7. Broken in and serviced regularly.

The drive operates fine. I have started to notice a rattle type sound that doesn't change with RPM or if it is gear or not.

This weekend after a short run I was at idle, in neutral and FELT and heard a loud knocking like a slamming noise. This can be felt through the whole boat like something was hitting the transom. Engine idled fine and didn't stumble or anything. There was no real rhythm to sound.

Trying to localize the noise it seems to be coming from the upper unit. After shutting down looking around with the drive up nothing seemed out of place.

Lowered the drive and started up again. In gear at idle the noise continued, slightly adjusting the drive trim made no change, nor does turning the wheel side to side.
Noise happened for a while then just stopped. I ran the boat at 3000 on plane about 5 miles with no noise. Fished for a while occasionally shutting down then and restarting for my drift.

Noise came back so I decided not to push my luck. Drove back 6 miles to port heard it only once or twice again.

Went back this morning and started it up but no noise.

I'm pretty convinced it's the upper unit starting to go but not sure what parts internally would cause this.

Since the 4th is coming I (unfortunately) ordered a new drive and plan to send this back for RMA once I pull the boat and get the serials.

Any idea what may cause it?

[admin]

That is odd that the noise is not more consistent. If you think it is the upper, you can pull the top cover easy enough to look at the gears. If it has lost a tooth, it could definately make a clunking sound, which might be more noticable at idle, but I think it would be consistent.

You can also check the magnet in the lower and see if anything looks funny there. a little metal is fine, but there should be no chunks.

Tech Support

[stevecti]

OK I pulled the boat. Very surprised the noise wasn't more consistent. More surprised the drive was even operating.

Drained the lube, lots of little metal shavings on the magnet. I had to wipe most of them off to get the plug back in. Lube has a metallic sheen everywhere. Pulled to top cover, found small chunks of metal. Didn't rotate to check all the gears.

Separated and removed the lower. Unit has some roughness when turning by hand and feel some play on the output shaft.

Pulled off the upper. Lube poured from bellows area. Tons of play and very rough when turning the drive shaft. Guess what ever is broken in the upper got bad enough to cause the play and damage the seal. The slamming must have been occasional binding on the case.

The good things are there wasn't any sign of water intrusion, gimbal bearing is good, and I was able to get the boat in without being towed:)

I'll be setting up an RMA. I ordered a new complete unit the other day in order to get back on the water as quickly as possible. Figured it wouldnt be a bad idea to have a spare. Hoping these last longer than they have.

That is odd that the noise is not more consistent. If you think it is the upper, you can pull the top cover easy enough to look at the gears. If it has lost a tooth, it could definately make a clunking sound, which might be more noticable at idle, but I think it would be consistent.

You can also check the magnet in the lower and see if anything looks funny there. a little metal is fine, but there should be no chunks.

Tech Support