shaft or transmission vibration

[dvd]

I have a 74 cal 3-30 with atomic 4. I purchased it in the last year and have since put on a new bottom and a new martec 2 blade folding prop. I get a considerable amount of vibration when under way. The engine is smooth at an idle and seems run well. It has a 2 to 1 reduction tranny. I can push the boat a little harder than I care to and the vibration subsides. So I only get it at lower cruising speeds. Reverse is fine. I had the opportunity to go out on a old cal 2-27 with an atomic 4 and it was very smooth in all areas of operation. It appears to be something in the shaft or transmission. I had the shaft alignment checked and was told it was ok.

Any suggestions

[msmith10]

I don't think I can suggest anything you haven't already thought of. If your alignment is truly OK (you can check this yourself-- it's not difficult), then another possibility is the cutlass bearing. On my boat, the motor mounts are solid without any rubber cushioning, and these are mounted to stringers glassed into the hull, so all the vibration is transmitted directly to the hull and is very noticeable. I used to have a Martec folding prop and changed to a fixed prop. The Martec gave more vibration than a fixed blade prop.

[SEMIJim]

Any suggestions

Is it really a new Martec folding prop, or is it just "new to you?"

We had a similar problem on our Pearson 30, except the vibration started at higher RPMs and only got worse. Attempts to speed up too far or too fast resulted in cavitation. Reverse was barely effective. After trouble-shooting the reversing gear, checking for shaft runout, checking the cutlass bearing and checking for fouling, we came to the conclusion it had to be the prop. We swapped it out for the original fixed 2-blade and the problems went away.

Martec folding problems with even a small amount of wear can get "funny."

Really bad shaft runout is easy to detect: Just put your hand on the packing gland while the prop is turning at low speed. If you don't feel excessive vibration, it probably isn't shaft runout.

Did this happen with your old prop?

Jim

[dvd]

shaft vibrations

Yes, the martec folder was just purchased new from martec. It is not a used prop. The original prop that was replaced was a 2 blade fixed which was the exact same size as the folder which was size martec recommended. I get get good speed its just that it is not smooth underway until I reach a max cruising speed then it seems to smooth out. No problems with reverse as it is very smooth. The boat does have actual motor mounts and is not bolted directly to the stringers. (prbably original) Some people tell me it's just the way it is but Ive been on a boat recently that ran very smoothly. Thanks for your input. I may have to have someone who really knows take a look at it, but it seems strange that mine would vibrate and others would be smooth.

dvd

[dvd]

shaft vibrations

Yes, I experienced the same vibrations with the fixed prop that was replaced with the new from martec 2 blade folder. In replacing the prop I had hoped the problem would have been taken care of but apparently not

dvd

[dvd]

shaft vibrations

One more thing is response, the cutlass bearing appeared to be in good shape as the boat was out of the water in Sept. The shaft had no play in it and was very tight in the cutlass bearing so I ruled out replacing it.

dvd

[msmith10]

I would agree with the cutlass bearing. If there's no play in the shaft at the bearing, I'd leave it alone.

[policecentral]

This will probably raise a fuss...

but I cannot understand the reason to replace a fixed wheel with a folding prop. The ads will say you might get .25 knot or so speed increase, but I want the comfort of a working propulsion when there is a lee shore or during docking/backing, rather than a jammed folding prop. Regarding the speed increase, most of us make mistakes in sail trim or simple inattention to make the supposed speed increase irrelevant anyway. And, at speeds lower than four knots, it is questionable whether the folding prop will actually "fold" anyway. To me, it is taking a truly reliable, quiet device (the fixed prop) and replacing it with a noisier and an admittedly far less reliable "folder". In any sailboat, that to me is never a good idea.

And everyone that I have talked to about "folders" is that you do sacrifice and power (particularly when backing down) performance to boot.

If I am missing something, I am confident that the group will correct my thinking...

JSM
Ranger 30 Northern Light
Savannah

[rigspelt]

The only advantage I can see is in racing, or very long haul cruising. In racing they might knock off a penalty for a folding prop anyway. Most of us doing short to medium range coastal cruising probably would not notice the small speed advantage, given all the other variables.

[dvd]

folding prop

In reply to police central there is a world of advantage to a folding prop over a fixed prop. The main reason being drag while sailing. A folding prop can give you a 1/2 to 1 knot more boat speed under sail which over the course of only several hours is a horizon job on a similar boat with fixed prop. After all arent we sailors because we like to sail or are we all wanna be power boaters. I dont know about you but I would rather sail my boat any day rather than motor it. The motor is only used so you can get your boat into position so you can sail. Also, I am a racer that has taken up a bit of cruising but you know the old tale. Whenever there are at least two boats sailing in the same proximity in close to the same direction a race is on. I like my boat to sail as fast as possible.

dvd

[SEMIJim]

dvd is correct. Our Pearson P30 came with a Martec folding prop installed and the original 2-blade fixed prop "on the side." Last season the Martec developed the so-called "Martec blues," and we had to replace it with the original 2-blade fixed prop. Forward performance under motor isn't significantly better. Reverse is somewhat better. (Mainly noticed in backing down, rather than actually going in reverse.) So, from a strict motoring perspective: Not much difference. In sailing, however, there's a BIG difference. We've noticed a definite performance hit under sail, especially in light air. We were given 12 seconds on our PHRF rating (we club race) and I'm here to tell ya: It wasn't near enough .

I think if you're just day-sailing or coastal cruising: Yeah, you probably want to stay with the good ol' reliable, tried-and-true fixed prop. As policecentral said: Who needs the grief? But if you're at all interested in performance under sail, esp. in light air, a folding or feathering prop will give you pretty significant performance gains, in our experience.

We were going to send our Martec in for a rebuilding/reconditioning quote. But what with the economy and a financial hit we've taken, it'll probably have to wait.

Jim

[dvd]

shaft vibrations

As my shaft vibrations continue I am going to pull the boat out of the water replace the shaft and have the prop (new from the martec factory in 9/08) professionally balanced. This plan is the only way I can achieve smooth operation under power. Once again I will NOT give up the under sail speed increase I get with the folding prop. Before I bite the bullet on this any last minute responses to my vibrations and does this plan appear to be sound.

dvd

[dvd]

folding prop

In response to semijim, I believe the phrf hit you take on a folder over a fixed is actually only 3 points. Obviously well worth it.

dvd

[SEMIJim]

In response to semijim, I believe the phrf hit you take on a folder over a fixed is actually only 3 points.

Our boat's PHRF rating with the Martec was 180. With the fixed prop: 192. PHRF ratings vary from club-to-club, but those are common numbers for our boat. And I'm told 12 seconds is a fairly common difference in PHRF ratings between fixed and folding/feathering props.

As regards your other question: I can't speak to the balancing of the Martec. Seems reasonable, I guess. Wrt pulling the shaft: Before doing that I'd have the runout checked. You've already checked shaft/engine alignment, you say. In fact: I'd have the prop balanced before pulling the shaft, whether you have shaft runout checked first or not. Reason is: Plenty of people have had lots of problems getting things right again after pulling and re-installing or replacing their prop shaft. I understand getting the alignment right is as much magic as it is science.

Funny thing is: On the one hand you say you had this problem before installing the Martec prop. That would point toward it being something other than the prop. But the fact that the vibration only occurs w/in a certain range would not indicate to me a shaft alignment or runout problem.

I wonder... I wonder if it's the engine, itself? Perhaps Don can comment on the likelihood of that.

Jim

[dvd]

semijim

My cal 3-30 has a 156 phrf and will get a 3 second hit for the folding prop I believe. You're right that different clubs will give different handicaps depending on type of boat, sometimes its win record, condtions, e.g. flat water etc. I sail and club race out of the stockton sailing club which is on the San Joaquin Delta which is part of the river system that flows into the San Francisco Bay. Because we have primarily light wind im working on phrf committee to increase my #. I still have a 72 cal 27 pop top that I use primarily as a race boat and although it has a 180 phrf it will ordinarily sail circles around my larger and heavier 3-30. dvd