Advice on serviceability of Volvo folding prop

[DarthPablo]

Hi All,

I've just taken the plunge and bought my first boat, a Bav 38, which I'm really pleased with but have much to do and learn. I obviously had it surveyed and one of the things the surveyor picked up on was heavy pitting in the Volvo Penta 3 blade folding prop stating he thought it was serviceable but would need to be replaced in the next 2 to 4 years. Now, the engine and saildrive seals etc also need servicing and I've had a quote from a local engineer who has told me the prop is shot and needs to be replaced. An equivalent replacement is going to be quite expensive, and they are saying that, given I'm new to sailing and mostly going to be sailing locally, it'd be better to fix a cheap 3 blade fixed aluminium prop rather than risk leaving this one on. The problem as they see it is not the pitting on the blades but the wear on the gear saying that if one of the teeth on the gear broke, the propellor could get jammed, maybe with one blade at an odd angle leaving me with loss of power or no drive at all. 

Now, I'm relatively new to sailing and not a marine or mechanical engineer, but I'd have thought most of the forces on the blades were rotational and that there wasn't much force on the gears themselves, but I'd be happy to be corrected on this point. It does seem to be a bit odd that the surveyor would have such a different opinion from the engineers, and I don't like to be cynical but can't help feeling that the engineers are just trying to sell me a new prop. One point is that the anodes on the prop were completely gone at the time of the survey so the boat had another 8 weeks in the water without anodes before the engineers saw it, so there will have been a bit more erosion, but in my eyes there doesn't seem to be much difference since the day of the survey.

Here's a link to a Google photo's album with some photos on the day of the survey and some from today: https://photos.app.goo.gl/RvrRZyvVsaavgKfw6

I did look for a Volvo prop or a general prop forum but couldn't seen one that seemed that active.

Any advice greatly received.

Paul.

[Symphony]

I am afraid that is a classic example of what can happen with a Volvo folding propeller. They are well known for corrosion because of a combination of the poor type of alloy used and the small size of anodes fitted to try and prevent corrosion. I expect in addition to the pitting (which weakens the blades) and the worn gears, there will likely be wear in the bores in which the pivot pins run. It is unlikely that it can be repaired/rebuilt economically, but if you are in the UK you could try a specialist prop company such as www.darglow.co.uk for an opinion.

I tend to agree with the surveyor - it is unlikely to fail completely, but the risk as the engineer says is that one of the teeth breaks which will jam the mechanism. The process of dezincification means the zinc in the alloy is leaching away leaving predominately copper which is soft and weak. That is what the pitting on the blades and hub is, but as well as being on the surface it can be inside the casting making it weak. Problem is you can't tell without cutting it up! You may well also find it is noisy and "bangy" because of the wear.

Personally I would not risk it and would fit a standard fixed prop. Not expensive (relatively) and in reality what most people have. If after you get to know the boat you feel there are benefits for you in having a folding or feathering prop then there are much better products available than the Volvo prop, in particular that are made of better materials and don't eat anodes or corrode to the same extent. If you look around you are likely to find that the most common folding props on saildrives are FlexOfold, and feathering are Maxprop or Featherstream.

Good luck with your new boat - sure it will give you years of pleasure.

[Holger]

Hi Paul,

I am not too familiar with props but I would have little trust in yours. While the hub from my perspective as a layman looks pretty good the blades do not. Attached please find a Volvo Penta parts bulletin matching different type numbers. If I understand correctly you should be looking for 16X11 blades (3583374). A blade kit is currently available at a German online shop at EUR 700 (compared to about EUR 1,500 from official Volvo Penta dealerS9: https://www.geboote24.de/boote-motoren/volvo-penta-3583386-propeller-ersatzblaetter-16-x-11-lh-3-blade-prop-kit/a-133437 The website is apparently in German only. Occasionally I have ordered some pieces from that shop at prices sustantially below those offered by others. They appear to buy stock from traders that go out of business and sell their inventories.

Besides, we had the hub of our folding prop repaired by a specialist and he advised and showed me that these parts are not made for eternity. While the hub looks rock solid from the outside there is a piece made of rubber inside and this is subject to wear and tear or even damage if a rope is caught by the prop or the prop hits something hard like a big piece of wood. Before you spend money on your current prop I would recommend that you have it checked by a specialist to understand whether it makes sense to spend money on it. Ohterwise, it is as in all other cases, you can only make yourself believe that a huge amount spent today will amortize over time - welcome to sailing.

Best regards Holger

[Captain Jan]

Hi Paul,
I have posted elsewhere on this forum ref. prop. experience, on a boat very similar to yours. The conclusion was the feathering prop was very good, transforming the sailing performance from when we had a fixed prop.
Ref. your existing prop, hopefully the surveyor is giving an observation based on his experience.  So, a detailed discussion on his experience of this specific issue would make you feel better, should you choose to keep it. But if the gearing is intact, the system proven to work, the tooth clearances good to the surveyor’s experience, it may be better to get a seasons use out of it, to find where the issues for investment in the boat actually are. Prop. changes may be straightforward, but they can become projects.  A previous reply mentioned to go for a fixed prop for safety in the short term, which is a very valid comment.  But if you want to sail, the feathering prop is so very good.
You mention, in passing, saildrive & engine seals need servicing- this could mean replacement. The hull seal may be straightforward but costly, but it may be the prop shaft seal has scored the shaft so it’s not a simple seal change. The discussion will then be about shaft sleeving which may or may not be sleeved in the right place on the shaft, or prop shaft replacement, then there are the issues of the drive shaft shims & on & on it goes.  And that’s only if there is nothing major. So it may be a good plan, for the first season, depending on your discussion with the surveyor, is “if it ain’t broke don’t fix it”. 
Best of luck with the new boat- you will love it!

[DarthPablo]

Dear Symphony, Holger and Captain Jan,

Sorry for the delay but many thanks for taking the time to reply!

There doesn't seem to be any play in the pins where the blade rotate but it's all a bit moot as who knows when I'm going to be able to get back to the boat yard, let alone get her back in the water (she was supposed to go back in yesterday but of course, that didn't happen). I guess, if that's my biggest worry - I'm pretty lucky!

I do have the prop at home, so I might try cleaning it up anyway and seeing how it seems once it's a bit shinier. I definitely want to be sailing and not motoring so feel a folding/feathering prop will be of value, but I don't really want to shell out loads now so I'll have to weigh up the risk and maybe plump for a fixed prop for a while. As you've mentioned, there will always be lots of expenses, so I guess it's deciding what needs doing most and where I'll get the most value.

I'd already been out quite a few times during the 6 weeks I had her before she came out of the water, including a few times on my own, so I'm sure you're right that there'll be lots of fun to be had for years to come. I've actually been enjoying cleaning her up and fixing a few other things too, which I didn't expect to enjoy so much.

Thanks again,

Paul.