loud whine at 2400 rpm

[Earl Miller]

I bought "Golden Girl" (hull #923) two months ago and have put 30 hours on the engine (current hours are 2480).  It has developed a high pitch whine at 2400 rpm.  This only happens in forward, not in neutral or reverse.  The service people I am using say it is the transmission and recommend that I replace it, the shaft and the bearing in the strut.  The previous owner had the shaft straightened several months ago and the mechanic feels this was a contributing factor to the problem (that plus age).  Does anyone have any suggestions .... do I carry on and have the work done (about $3,000) or are there other possible causes that should be explored first?  I have checked the forums and tech notes and have not found a similar problem.
This Web site have been great for a new owner .... thanks for all the information .... past and future.
Earl

[Ron Hill]

Earl : You didn't mention why the PO had the "shaft straightened"?? you can take the shaft out and roll it on a flat surface and see if it's in round.
Here are a couple of things that I'd try:
1. Replace the cutless bearing and make sure that the leading edges of the prop are blunt (vs sharp)
2. If the problem still exists, you might change out the shaft.

When you hear the whine go into the aft cabin and use an old mechanics trick.  Take a screw driver and put it on the strut nuts and put the handle end to your ear(or use a stethoscope if you have one) and see if it's the cultless/prop.  Then put it on the transmission case and see what you hear.  Changing out the transmission would be the last resort!!  I'd guess that I could change out the cutless ($45 + labor) and a new stainless shaft ($175 + labor) at much less that the yard's estimate. (Both are avialable from Catalina)

Our site instructs you how to do both jobs and they can be done in less than a day if you have the parts.  I've done both - look in the C34 Mainsheet Tech Notes.
Hope this helps.   

[Stu Jackson]

Earl

From a purely analytical approach, without "hearing" your noise.

1.  Where's it coming from?  Inside the boat would be a possible, but not necessarily resultant, transmission issue, since the Hurth is inside the boat.  Outside would lead to thinking of the bearing.

2.  Was the cutless bearing ever changed by the PO?

3.  Have you checked and/or changed the transmission fluid?  Usually, if it looks good, it should be good, so you may want to check that first.

4.  Have you run over any sand recently?  A few months ago, a friend wrote and said he'd just had his cutless bearing replaced.  It worked fine for a few months, then all of a sudden started making strange noises.  I asked him if he'd gone aground.  Hmmm...  I suggested he use the boat, and find some clean water and go back and forth.

5.  Is there any reason to believe that the shaft was NOT straightened?  Who did the work?  Still under warranty?

6.  Is the engine aligned?  Have you checked the plates?  Is the stern tube intact?  Is the stuffing box lubricated and working properly?

There are all sorts of "things" back there.

Before you spend that kinda $$, I would recommend seeing if you can start narrowing down the issues, and reduce dependency on a yard that seems to want to spend your money.

Good luck, and keep in touch.

[Ray & Sandy Erps]

Greetings Earl,

Hear's a link to my previous inquiry on the propellor ring.  The leading edge on the blades are too sharp and the noise got quieter and quiter as the propellor slimed over so I never put on my wet suit and jumped in to file off the leading edges.


http://c34.org/bbs/index.php?topic=2401.0

[Earl Miller]

Thanks for the speedy replies .... Ray Erps (the PO) is suggesting it is the leading edge of the prop that was balanced last fall.  It will certainly be worthwhile grinding the leading edge and testing it ... how much should the edge be rounded?  Should this be done by a prop repair shop to ensure it stays in balance?
The cutlass bearing was replaced last fall as well so it should be fine. 
The noise is very high pitched so it is hard to locate - it does seem loudest at the stern.  I will try the screwdriver approach to see if I can narrow it down.
I have not checked the transmission fluid - Ray, when was the last time you changed it?
Earl

[Ray & Sandy Erps]

Greetings again Earl,

Glad to hear you're getting some sailing in with Diamond Girl.  I changed the transmission fluid last summer.  Should be in the log book and there should be a container of the remaining fluid tucked in along one of the stringers in the engine compartment. 

My recollection was that the propellor shaft was .008 out of true when I hauled in last Sept.  The yard said it was borderline whether it needed to be straightened or not.  I had them do it since the boat was out already and I was going to replace the cutlass bearing anyway.

The only other funny noise we experienced from the drive train was a horrible loud screeching/squeeling noise when an air pocket got trapped in the drippless seal.  First time I heard it, I thought we caught a crab pot line or something.  Always burp the seal after haul outs or when a diver scrubs the bottom.  I found that even the air bubbles from my SCUBA gear would trap a little air in that seal pocket.  To burp the seal, pull the access cover to the propellor shaft, grab the rubber belows aft of the stainless collar on the propellor shaft and move it aft a bit and let about a cup of water squirt out.  That should remove any trapped air and has taken care of that awful noise.  You can do a search on the board to find a discussion on that particular noise as well.

[Ron Hill]

I believe that you two guys can "hammer it out" and don't need me.  OUT!   
BTW - If it's too sharp a leading edge, all you need to do is take a file and flatten that edge.  It's something you can do yourself.