LOUD rattle in 35-3

[Cory B]

Hi all,

We have a VERY loud rattle in our 1984 35-3. It only occurs when the engine running near or at full speed cruise and the water is lumpy. We can't reproduce it at the dock, even in gear, so its been hard to pinpoint.

It sounds like its under the galley floor or under the sink along side the engine. Is it possible for the floor to rattle itself? Putting pressure on different areas of the floor and on the ladder sometimes changes the rattling pattern, but nothing concrete. It doesn't feel like a cavitating prop.

Any thoughts?

- Cory

 

[Shadowfax]

Cutlass bearing. Motor mounts Misaligned prop shaft caused by either of the foregoing. Uneven marine growth on prop. Picked up something on the shaft, or prop throwing it out of balance.

Of course if it does it while under sail and the engine off, disregard all of the above

 

[Cory B]

Don't think its its the drivetrain...

I don't think its the drivetrain (but I could be wrong), but internal joinery. We got into the lazarette when the rattle was going on, and it sounds like it mid-engine block or further forward - but was really hard to isolate any further than that. We had new engine mounts, shaft, cutlass, maxprop, alignment last fall, but really hadn't put the engine through its paces until recently. And unfortunately since the boat was new to us, I don't know if the noise happened previously.

We had a diver underneath the boat yesterday (to remove a line we tightly wound around the rudder post caught about 40 miles away from nearest harbor off Washington coast), and he said shaft, strut, prop, etc. all looked good. The noise was occurring long before we caught the line.

This one really is aggravating us.

- Cory

 

[Ernest]

Do you have a drip free shaft seal? If so, burp it by compressing the rubber and letting all air (and some water) out of the coupling. If there is any little bit of air in it, slowly but surely on a long run under power, the water in the coupling will start to spin with the prop shaft. If there is a bubble of air inside it will give you the same symptoms as an unbalanced shaft or prop. Anyway it's a no cost, 5 second fix. Check it. Ernie Schlesinger

 

[Rocinante33]

Galley stove

Cory,

Our stove rattles a lot when we motor. Strategicly placed rag bits can stop it if it is the racks in the oven or the door itself doing the rattling.

Keith
E33

 

[Brisdon]

Bad engine mounts can cause the engine to throw itself back and forth at a certain rpm even though it's aligned. Also, it might just be out of alignment. Just because someone aligned it, doesn't mean it took. Maybe a nut slipped, maybe the mechanic wasn't acurate. Could be the feathering prop too. If you've checked alignment and checked the mounts and everything's ok, I'd then throw a fixed prop on it and take a run and see if it doesn't clear up.

 

[treilley]

The floor on my 35 was not glued down. Only screwed,although it never rattled. All of the cabinetry is isolated from the sole with the exception of the frame on the front of the engine housing. It just sits on top of the sole. There is actually teak trim behind this that is hidden by the frame itself. Not sure why but my point is that this frame could be rattling againt the sole. It is fairly simple to remove and check. There are 2 trim strips behind the ladder port and stbd. Remove these to expose the 8 or so screws and them the whole frame will come out. Run the engine at the rattling speed to see if there is any difference.

 

[Kim Schoedel]

Cory, we have the same boat. Do you have engine access panels from under the galley sink to the motor? Ours were a bit loose when we purchased the boat, took me a while to figure it out because it wasn't consistant. But finally when the noise came on, I was able to rush down below and start putting my hand on things under the sink until I found the culprit.

Also check to see if any hose's under the sink are laying real close to the hull or that little bulk head between the starboard lazerette and under the sink, stuff a rag or something soft under them and see if you can illiminate the demon.

One other thing, check the large ice box. You probably have the drain shelf on the bottom and the two shelves inside. Are they rattleing? The weight of food and cold beer helps to calm them down.

 

[Cory B]

Thanks!

Thanks for the ideas everyone, we're going to drive out to the boat today (its 3+ hours away right now) and see if we can solve this one.

- Cory

 

[Cory B]

Problem Solved!

In case any one is curious, the problem turned out to be the raw water pump. The pump was one of those with a carbon/graphite shaft bearing (no grease cup), and there was a lot of play between it and the shaft. I'm not really sure why it only appeared while under way, but we've motored about 35 hours in a variety of conditions since replacing it last week, and the noise is gone.

- Cory
http://svbalancingact.blogspot.com

 

[Frank Langer]

Cory, thanks for taking the time to update us. This may be helpful to some of us in the future.
Frank.

 

[Sean Engle]

Cory,

Our stove rattles a lot when we motor. Strategicly placed rag bits can stop it if it is the racks in the oven or the door itself doing the rattling.

Keith
E33

The stove on my boat made a ton of noise also...

//sse

 

[George Foose]

Prop Shaft Knock E 38

In the last month since getting Free Wind back into the water I have used the boat on two long week ends. Both times There is a noticeable knocking or rattle at nearly all RPM's coming from directly below the steering seat. When I zig zag steer is the only time the knocking stops. When I inspect the coupling area under power this knock cannot be heard. I therefore suspect it is coming directly from the prop. The strut has a new cutlass bearing. The three bladed feathering prop is the Sail Prop originally installed by PSC in 1994.

Does anybody have any trouble shooting ideas? Should I just assume the prop has become too loose with age?

 

[treilley]

My first guess would be that the zinc has loosened up.

 

[Sean Engle]

My first guess would be that the zinc has loosened up.

Mine did that also - make a terrible knocking sound - at first I thought it was the Hurth transmission - but it was only the zincs - 30 min and a wetsuit took care of that!

//sse

 

[George Foose]

Ericson 38 knocking

Well I found out what the RPM sequenced knocking was. Pulled the boat to install new Seahawk 3 bladed feathering prop (17 X 11.5) and was surprised by the attached. Looks like I better become educated on electolisis and galvanic corrosion and its prevention.

Here in Thailand the complete replacement of the strut has to be done in stainless steel.

 

[obiwanrazzy]

Good lord! That ain't right...

 

[Frank Langer]

OK, so can someone explain what might be happening to cause this--the first picture way above shows what I think is a pretty normal set-up, with strut, prop shaft, zinc on the shaft, and prop also with a zinc. Yet he is having this problem and attributes it to electrolysis. (I'm not sure his diagnosis is right, but I'm not sure).

I am not aware that many people put a zinc on their strut, and yet the strut wouldn't be protected by the prop shaft zinc, as the cutless bearing would insulate the strut from the shaft, wouldn't it?

So, just when I thought I was beginning to understand this stuff, I'm having more questions....

I'll appreciate it if anyone can shed some light on this.

Frank.

 

[Jeff Asbury]

zinc on my E-27's strut

I have always had a zinc on my E-27's strut. Smaller strut though.

 

[Cory B]

bonded?

I am not aware that many people put a zinc on their strut, and yet the strut wouldn't be protected by the prop shaft zinc, as the cutless bearing would insulate the strut from the shaft, wouldn't it?

On our previous boat the strut was bonded to the boats bonding system (and hence to the shaft/zinc). I'm not sure if thats the case on our 35-3.

-Cory