Mainship Prop? / Stuffing Box Vibration

[jimL]

I have a 2005 Mainship 430 aft cabin trawler with twin Yanmars. When we purchased is last year there was a very slight vibration with the port engine above 2000 rpm.

This year the vibration has gotten worse, to the point where I do not run the engines above 2200 rpm. At anything above 2200 rpm, the stuffing box assembly where the stuffing gland is located jumps around by at least .25”.

We’re pulling the boat tomorrow to check for prop damage, although both props were trued immediately prior to the purchase last May (I have the documents and saw the repaired props installed).

My question pertains to the rubber hose that makes up the “stuffing box”. It is 12 years old and bulging between the forward and aft clamps. When I observed the unit ‘jumping around’ at over 2200 rpm, I became concerned that hose would bust resulting in a catastrophic failure. See here for a pic of the stuffing box, I changed the clamps a month ago – this is an older pic, but shows the rubber hose:

http://i258.photobucket.com/albums/hh254/lakesponge/Mainship 430 Aft Cabin Trawler/Port Stuffing.jpg

I provided the yard today with my intent to have the rubber hose stuffing box replaced (at considerable effort and cost). While they have everything apart, they are going to replace the cutlass bearings as well.

Am I being too cautious?

Has anyone replaced their rubber hose stuffing box?

Has anyone had a failure with this critical component?

Thanks

JimL

 

[psneeld]

No, only a methodical approach will negate the vibration.

Replacing the hose is relatively easy. Either shaft in or out...most of the time.

Cutlesses can go with a bit of slop for awhile if your shaft turns fairly slow, say less than 1000 at cruise...

 

[ddalme]

jiml
Unfortunately, there are a number of things that can cause the vibration. Bent shaft, engine alinement, prop balance, and cutlass bearing. Hopefully the yard has an experienced hand that can hopefully find the problem. Good luck.

 

[RT Firefly]

Greetings,
Mr. jL. Am I to understand you are going to have both the hose AND the stuffing box replaced? The hose, for sure. Should be quick and cheap but why the stuffing box?

As messrs. ps and dd state. Vibration elimination will take a methodical approach which should investigate any number of causes. Before the yard disconnects anything they should do a visual on the cutlass bearing and they can put a dial indicator on the shaft. If those two items check out, have the prop checked and replace the rubber hose although it doesn't LOOK too bad. For the little added cost, why not replace it for piece of mind.

The hose is simple: Disconnect shaft from flange, slide shaft aft, disconnect aft rubber hose clamp, slide old hose AND stuffing box off shaft. Installation is a reversal of the above process with the replacement of the rubber hose and perhaps a repacking of the stuffing box being the only NEW items. With that much room, even I could probably do it in 3 or 4 hours.

Again as mentioned, have your engine/shaft alignment checked.

 

[jimL]

Thanks all for the quick replies. I have found that I can alway count on members to offer quick replies.

We will check the engine alignment, and prop for straightness in accordance with the dial indicator method.

Point of clarification, I'm not looking to replace the stuffing box, but just the hose that connects the stuffing box to the packing gland component. I have/am replacing all raw water hoses this year to baseline the vessel. When I took off the raw water generator hose this weekend, it almost fell apart in my hands due to age and use. That make me concerned about the other critical hose components (like the one in the pic). All other raw hoses have been replaced in the past 2 months.

And yes, one step at a time in determining the causes for the vibration.

We're located in the Hudson River just South of Albany and the river is full of debris due to a LOT of rain. Lot's of submerged logs etc, but I don't recall hitting anything this year or last year.

Jim

 

[DavidM]

I am sure that the yard knows this, but that hose is a very thick, multi-ply hose made especially for this service. Buck Algonquin sells them by the foot in various sizes.

David

 

[boomerang]

Maybe you'll get lucky & it's a piece of rope or something in the wheel. Have you done a visual on your engine mounts? Collapsed mounts aren't an uncommon occurrence. If it had a slight vibration originally then got progressively worse, that's one thing I'd look for.

 

[ddalme]

Oh yes-check for tightness in your rudder bearings-almost forgot that.

 

[jimL]

We performed a sea test today with the mechanic and my wife piloting. He assured me he thinks the vibration is caused by a dinged peddle or two on the port prop. The boat is being hauled tomorrow for the prop inspection and possible re-tuning.

The mechanic also said the rubber hose that connect the packing gland unit with the stuffing box is fine and that it is VERY thick and rarely fails. Based on the sea test, he doesn't think the cutlass bearing is bad, but will inspect tomorrow. More to follow.

Thanks for the tips (rope in the prop) and support.

I do not have a spare set of props, but as we work closer to full time cruising, I need to acquire a set. Does anyone have recommendations of where to purchase a set of Hy Torque 25 R 25 MY-T4 props. (I'm just learning about these props).

Jim

 

[jimL]

The boat was hauled and the mechanic indicated three pedals on the port prop were noticeably dinged. The propers were set out to repair and we hope to be be back in the wattle by Wednesday. He indicated that all other components looks fine.

Any recommendations for a source for "spare props"?

Thanks for the assistance.

Jim

 

[boomerang]

They must be some serious blade "dings" to see all of that movement at the stuffing box. Years ago I bumped bottom with a sportfish I owned & curled one of the blade edges 90° and could barely feel any vibration at all!
Regarding spare wheels, keep an eye on ebay, the classifieds on this forum or craigslist.
Here's a link to a place that brokers wheels without a home but I have no experience with them.
https://www.propellerplace.com/
Good luck & keep us posted.

 

[Ski in NC]

Not all prop "dings" are the same. Seen some blades folded badly that barely shook the boat, seen others that looked super minor and shook badly. Get them tuned up and see what you get.

 

[jimL]

Hi All,

Just to close this out for now.... The props were out of spec by 5 degrees on all pedals on one prop and a few degrees on some of the pedals on the other prop.

We took the boat out and saw a difference and the vibrations have subsided, although not completely. I think part of the challenge on my part, new to inboards, is to learn how much of a slight vibration is 'normal". We'll spend the rest of the season learning and documenting and will re-inspect when the boat is hauled in the fall.

Thanks as always, to this forum for the insight and recommendations.

Jim