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Old 07-05-2008
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Prop/Transmission Issue

Hi All,

We have a 1976 Pearson P30. A4 is original (we assume). She has a Martek folding prop of unknown vintage.

Coming back from our first, and, so far, only , sail this year, several weeks ago, we experienced a problem that felt like the prop was fouled, and we couldn't seem to clear it. Would've found a place to pull over and dive on her, but had no goggles and the water was all of about 51 degrees F. Too cold for that. So instead we proceeded back to her slip as gently as possible. By the time we got back to the slip, and after a couple more gentle attempts to clear the prop, she was actually feeling normal again.

The following Sunday we took her down the canal a bit to check her out. She seemed to behave properly, sounded and felt right, gradually going up to 4 kts in the canal. Got to an open spot with a bit of maneuvering room and tried to accelerate. Engine revved-up suddenly. She wasn't popping out-of-gear. Did some more experiments. We can get her up to 6 kts (comfortable cruising speed in quiet water with no head wind), but it has to be done quite gradually.

Already had the Moyer manual. Bought the reversing gear DVD. (Highly recommended, btw.) Last Sunday: Went through it. She is clicking into forward firmly. Trying to tighten one notch results in shifting so stiff that my wife can barely get her out of forward with all her might. (It took all my strength to get it out of foward, from below, while working on it from the quarter berth.)

The neutral zone seems about right. We've had occasional problems with slippage in reverse, but I'm pretty sure that's because one of the overly-long plug wires keeps getting looped around the shift lever, preventing its full travel to reverse. (I'm going to order new wires from Moyer to fix that problem.)

At Don Moyer's suggestion, I replaced the 10W30 oil with straight 30.

Today I dove on the bottom to check the prop and shaft. All seemed well. Then we went out into the lake to see if the oil change had cured the "slippage" problem.

The problem remains

I am not confident the "slippage" issue is necessarily the reversing gear or that, even if it is, it isn't being provoked by something going on with the prop. Here's the thing: Under anything much above about dead slow, and when operating in reverse, we're not getting the power we should, there's excess vibration, and it just doesn't feel or sound right.

Here's another odd thing: As we were making a "U-turn," under moderate power, to head back in, during the entire turn we heard an unusual noise. It sounded kind of like a high-pitched buzz or low-pitched whine. The Admiral thought it sounded like the kind of sound we used to hear occasionally, running under power, when we'd cross large wakes.

I'm wondering if what we're experiencing isn't cavitation. That maybe there's something seriously wrong with the prop.

I'm thinking we're going to have to find somebody locally who know what he's about to figure out what's wrong with our boat, but, in the mean time, anybody have any thoughts on what might be going on?

Jim
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Update: Fellow club-member with many years experience sailing and on his third boat, I think, says the symptoms sound like an engine/prop-shaft misalignment. He thinks it's possible either the bolts holding the engine to the engine mounts have loosened-up, or the engine mounts themselves have come loose. He says he's seen both happen. He allows as how he's got no experience with folding or feathering props (doesn't trust 'em), so he can't say as to whether or not that might be the problem.

So now we're up to it being one or more of: Reversing gear (aka: "transmission"), folding prop, or engine/prop-shaft alignment.

Currently thinking of just calling a local place recommended by a couple of fellow club members and just telling 'em "Please, just fix our boat so we can go sailing sometime this season!"

Jim

Last edited by SEMIJim; 07-07-2008 at 12:56 PM.
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Thoughts off the top of my head: Alignment sounds like the likely issue though an under-pitched prop would exhibit the symptoms you describe.
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Can't help you at all with the gear, but some random thoughts..

The strange noise during a hard turn could well be cavitation... the rest of it makes me wonder if somehow the prop is not fully opening and may occasionally try to refold even under power... this is unusual but could account for the increase in rpm without "popping out of gear", as well as the sense of loss of power while motoring. Could there be something in the area of where the blades are pinned that you missed on inspection?

Alignment issues would cause vibration and unusual sounds as well, but if it's bad enough to slow the boat down the vibration should be quite excessive and leave you no doubt about what the problem is. Also I wouldn't expect alignment issues to occasionally "unload" the engine.
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From reading your post in another thread I think you're looking more at a prop issue. One of the cheap things that you can do is to listen with a stethoscope, or just a length of rubber gas hose, along the shaft and at the stern tube, with the boat tied up and operating in gear, forward and reverse. It's a quite handy way to pinpoint the origin of odd sounds and vibrations.
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Given a guess, and one that fits all the symptoms except the Moyer related stuff - I'd say the pitch on your prop is going off as is something broke and it's now varying between what you want and flat (the out of gear / rev up), the serious vibration (too much pitch, excessive load) the crappy reverse etc.
Doesn't even have to be all the blades, one would do it.

That's hard to trouble shoot in the water with a folding prop.
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Where's that neighbor's kid we were going to send up the mast with the Sailkote? We need to get him a mask and a weight belt.
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I'm just a little confused by one thing: I'm not sure if you used to be able to operate with no problem and this is something new, or if you're dealing with something that's been there a while.

Either way, before I started thinking about alignment, loose motor mounts, and other stuff like that, I'd have a diver who is familiar with folding props go take a real hard look at it.

My own boat, and old Morgan, has a two blade folding prop, and when it gets sufficiently clogged up with little organic nasties, it doesn't work right. If the blades aren't opening all of the way, or worse, if one is opening and one is partly opening. Then you'll get vibration, rude noises, low speed, all kinds of stuff.

Anyway, make sure the prop is opening all the way.

If you're worried about loose motor mounts, start the engine and rev it up in neutral while someone watches the engine. It shouldn't budge. If it moves more than 1/8", you've got a bad mount, loose hardware or something like that.

While you're tied up at the dock, put it in gear and look at the shaft, if you can. Once again, it should spin, not vibrate or move in any way up, down, left or right.

If you have one of those fancy anti-vibration couplers with the little rubber damper things between two steel plates, look at each of the rubber deals. I had one of those fail on a boat I was delivering once, and it set up a horrible vibration.

I guess I should have said this earlier. Tell your diver to check the cutlass bearing for you. It's easy enough. Hang onto the strut and try to move the shaft/prop. If they even budge, that's likely your problem. No up/down, left/right motion allowed at all.

Just about the last thing I'd suspect would be alignment, unless something else has given along the way. (Motor mount, coupler, etc.)

Before I went to the expense of pulling the boat to have the shaft fooled with, I'd bring the diver back and have him pull the prop. Send it out to a prop shop that can handle sailboat props. Ask around. I know of one down in Ft. Lauderdale if no one else does. He was even able to balance the AutoProp on Island Breeze, and that's something even the factory didn't do right!

Good luck and let us know what you find.
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Quote:
Originally Posted by Faster View Post
Can't help you at all with the gear, but some random thoughts..
We'll take whatever we can get at this point .

Quote:
Originally Posted by Faster View Post
The strange noise during a hard turn could well be cavitation...
That's what the Admiral thinks. To her, and her hearing is much better than mine, it sounded like a continuous version of what we'd sometimes hear when motoring at cruising speed when out on the lake and running across a large-ish wake from a power boat. As we'd cross the waves, we'd hear a bit of what sounded a bit like cavitation noise. The prop on our boat isn't all that far below the waterline. It was trivially easy for me to get to it when I dove on it last Saturday. I just took a breath, sank down a little, and pulled myself down to the prop via the top of the rudder.

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the rest of it makes me wonder if somehow the prop is not fully opening and may occasionally try to refold even under power...
Nobody I've talked to, so far, seems to know much about folding or feathering props. Certainly I do not. But a folding prop, like the Martec we have, seems like a pretty simple mechanism. Centrifugal force thows the blades out, no? In forward: The action of the blades against the water tends to force them forward? This is (one reason) why reverse is so much worse with a folding prop: Because all that holds the blades out is centrifugal force, and the direction of trust is actually trying to fold them?

Do (Martec) folding props have a failure mode such that, in forward, they tend to fold up, or one blade wants to fold up, under forward thrust? That would explain everything, I guess.

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Originally Posted by Faster View Post
this is unusual but could account for the increase in rpm without "popping out of gear", as well as the sense of loss of power while motoring.
Thing is: When the engine goes unloaded, I don't recall hearing cavitation noises. Then again: The engine is revving and your mind is reacting with "Holy sh*t" and has you heading for the throttle with all due speed.

Btw: When an A4 clutch assembly slips, nothing actually pops out of gear, it just slips until and unless you reduce power so the coefficient of friction takes over again.

Quote:
Originally Posted by Faster View Post
Could there be something in the area of where the blades are pinned that you missed on inspection?
It's possible. The water was exceedingly murky. The prop, blades, shaft, etc. were all just a murky shadow. I felt all over with my hands, as best I could. But there was no way I could actually see anything clearly.

Quote:
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Alignment issues would cause vibration and unusual sounds as well, but if it's bad enough to slow the boat down the vibration should be quite excessive and leave you no doubt about what the problem is.
Furthermore: You'd hear, sense and feel it at all speeds and under any thrust conditions, wouldn't you? If we power slowly and gently, reaching no more than, say, 4 kts, she feels pretty decent. Well, she used to. I'm pretty sure the problem is getting worse. On the way back this last time, anything over 3 kts felt wrong.

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Also I wouldn't expect alignment issues to occasionally "unload" the engine.
Nor would I, but I've little idea of what I'm doing, anyway .

Jim
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Quote:
Originally Posted by sailaway21 View Post
From reading your post in another thread I think you're looking more at a prop issue.
That is my favourite candidate at this time.

Quote:
Originally Posted by sailaway21 View Post
One of the cheap things that you can do is to listen with a stethoscope, or just a length of rubber gas hose, along the shaft and at the stern tube, with the boat tied up and operating in gear, forward and reverse. It's a quite handy way to pinpoint the origin of odd sounds and vibrations.
I used to have a stethoscope. Dunno what happened to it, over the years. I've used the rubber hose trick in the network racks at work, to figure out just which piece of network gear had the failing fan .

She makes no odd noises, sounds quite normal, in fact, when tied up and put in reverse or forward at idle. I'm loath to do that at more than idle, however, as the stern lines are actually only about perpendicular to the centerline, and there's no way to move than back. All that keeps her off the seawall is a lone spring line up to the front cleat.

Jim
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