Popularity of Saildrives

Stu Jackson · Mar 4, 2015

Stupidity of Saildrives

They suck.

They are only used 'cuz it is less expensive to build boats with them.

The seals require regular maintenance.

If not, there's a BIG f-ing HOLE in the bottom of your boat.

They're are NOT popular, they are disasters waiting to happen.

A really stupid idea.

weinie · Mar 4, 2015

Stu Jackson said:
They suck.

They are only used 'cuz it is less expensive to build boats with them.

The seals require regular maintenance.

If not, there's a BIG f-ing HOLE in the bottom of your boat.

They're are NOT popular, they are disasters waiting to happen.

A really stupid idea.

Why don't you tell us how you really feel?

Kings Gambit · Mar 4, 2015

I have one on my Bavaria 38; a Yanmar SD31. They are made of aluminum, so the "leg" needs to be well protected w/ zinc against electrolysis. Poor maintainence will lead to problems there. The leg is essentially the same thing as the lower gear drive of an outboard. Thus, the "gearbox" at the prop end is submerged, protected from seawater by two oil seals which can leak and admit seawater into the gearbox, potentially causing damage to the gears which are made of black iron, not SS. The lower gear oil can be changed completely only when the boat is out of the water and the oil has a "useful" life of only about 70 hr of operation. Go figure--that would amount to a haulout once a year just to change the lower unit's gear oil. The leg exits the boat through a hole in the bottom that is protected by a pair of rubber (or similar) diaphrams--an inner one and an outer one. IF the outer one allows water to enter the space between them, the water is kept from entering the boat itself by the inner one. An alarm indicating that the outer diaphram has failed is supposed to sound if that happens. The alarm is a conductivity alarm set off if both leads contact seawater, etc. Saildrives, in my opinion, are expensive to maintain.

So, what's good about them? They keep the price of the boat down b/c they are less expensive to install than a shaft needing support structures and alignment. The leg is vertical so the propeller is 100% "flat" against the water in the direction of travel, rather than lying at an angle to the direction of travel. The result is no asymmetric prop walk--the boat backs up straight right away; it also backs up fast. Since there is no loss of efficiency as with the angled props, there is more forward thrust per revolution--engine HP is more efficiently applied, meaning that the boat is typically much faster under power [at = RPM] than a boat of similar size and wt having an angled propeller at the end of an angled shaft. Also since there is no shaft there is no cutlass bearing to fail and no stuffing box to leak--the bilge remains dry.

I've replaced the seals on the lower unit (leg) once in 12 years of ownership w/ no evident damage to the gears even though water had entered. I replace the zincs twice per year; they're about $50 each. I change the lower gear oil in "partials" by sucking up about 2/3 of it from the top (fill) hole between haul outs when I change it completely from the lower plug. So far the diaphrams have not leaked! I love the speed, the manuverability, the dry bilge, and the fact that I got a lot of boat in the Bavaria at the price I paid--a good value purchase!

Ted · Mar 4, 2015

Kings Gambit covered the majority of pros and cons but here are a few more. Saildrives are being used by a lot of boat builders because of the simplicity of installation. Whether your boat has a saildrive or conventional shaft and prop, you will always have to do some type of maintenance. As far as I'm concerned a hole in the boat is a hole in the boat. When something fails with either design you have the potential for big problems.

I am in contract to purchase a new (used) boat and have been doing a lot of homework on saildrives recently. From what I have been told by people who have used saildrives for many years is that there is less vibration because the drive leg is somewhat isolated from the hull. Volvo and Yanmar both have similar designs. Volvo recommends that the diaphragm be replaced every 7 years. In order to do that, the engine has to be moved forward a few inches to remove the drive leg. On other boats, the engine has to be removed. I was speaking with a couple of insurance companies specifically about the diaphragm and was told that they would not insure a boat if the diaphragm is more than 7 years old. The boat I'm looking at has the original diaphragm which is 14 years old. The boat is uninsurable in it's present condition even though the diaphragm may not be leaking. Unless the seller is willing to replace it, I'm walking away form the deal.

Initially I was concerned about the safety issue of a saildrive but after seeing the actual diaphragm and how robust it is, it's no longer a concern. My surveyor told me that he has never heard of a diaphragm failure that caused a boat to sink. I would imagine it's a extremely rare occurrence and that more boats have sunk because of a failed/leaking shaft stuffing box on a conventional shaft drive system.

Change is sometimes difficult to accept but it seems that saildrives are becoming the drive system of choice for boat builders, like it or not. We'll just have continue to be diligent with maintenance in other ways.

Jackdaw · Mar 5, 2015

Ted and King pretty much nailed it.

ANY hole is your hull is a potential sinking if it goes wrong. The SIZE of that hole does not matter. If you are worried about that, glass them all over and get an outboard. As king notes, I'm sure more boats have sunk via propshaft issues than saildrive ones. I too have never heard of one failing.

Its proven technology that gets installed on million dollar boats, and not just because ease of installation. The utter lack of alignment issues is worth the price of admission alone. and as Ted notes, the lack of prop walk makes backing very easy. Our 36.7 drives better in reverse then it does in forward.

kloudie1 · Mar 5, 2015

If you are in a place where the boat is hauled each year, they can be inspected and checked for corrosion then. For places like the Gulf Coast, where the boat is in the water year round for 3-5 years at a time, they are not as good a choice. In my opinion, the leg corrosion is the biggest problem.. Seems to me that the legs should be made of an engineered, fiber reinforced polymer to keep them from corroding.. Being immersed would keep it plenty cool. The gearbox oil problem could be solved with a small standpipe about a foot above the waterline (inside the boat) so that the pressure in the gearbox is always above the pressure of the water outside. If the standpipe were clear, you could see when the oil was leaking out the seal. With all the good things about saildrives, I am amazed that the manufacturers haven't fixed two of the major ones that would pretty inexpensive to address.

Stu Jackson · Mar 5, 2015

WADR to those who have "done their homework" on saildrives, one hole in the bottom of a boat is NOT the same as any other. While both are obviously below the waterline, I'd bet I could keep the water out if I had a catastrophic failure of my stern seal (algonquin hose) a LOT easier than if I had the same failure of a saildrive seal. Lot easier.

OK, so they put 'em on million dollar yachts. They also put 4D and 8D batteries and alternator output routed through switches to the batteries on them, too. Both dumb ideas, too.

The "trick" is to do your homework as some have done, and make your own informed decision.

And, yes, in this case, I DO have an opinion.

:dance:

Ted · Mar 5, 2015

Stu, I think that the saildrive manufacturers have tried to address the issue/concern of the big hole in the bottom of the boat by incorporating redundant protection. There are two diaphragms protecting the opening. In theory if the outter diaphragm starts to leak, an alarm will sound so you have notice that it needs to be replaced. Meanwhile, the inner diaphragm will continue to keep the ocean on the outside of the boat. I know that my present dripless shaft seal bellows does not offer the same level of protection. It needs to be replaced periodically too but I would venture to guess that many owners do not adhere to the manufacturer's recommendations. I concur that it would be easier to slow the ingress of water if a conventional stuffing box were to fail but what are the chances that it will happen when you are on board? Maybe we should go back to outboard motors or better yet, strickly SAIL POWER!!!

Stu Jackson · Mar 5, 2015

OK, Ted, this forum is great 'cuz we both get to provide our opinions. That's why I said: "The "trick" is to do your homework as some have done, and make your own informed decision."

outboard - no holes
traditional shaft - hole, small
saildrive - hole, double seals with alarms, bigger hole

Your boat, your choice.

Good luck. I don't know if BO (the OP) is going to buy a boat with one (I doubt it

), but it was a good question.

Heck, Ted, I even have friends with saildrives!!!

woodster · Mar 5, 2015

Stu Jackson said:
OK, Ted, this forum is great 'cuz we both get to provide our opinions. That's why I said: "The "trick" is to do your homework as some have done, and make your own informed decision."

outboard - no holes
traditional shaft - hole, small
saildrive - hole, double seals with alarms, bigger hole

Your boat, your choice.

Good luck. I don't know if BO (the OP) is going to buy a boat with one (I doubt it ), but it was a good question.

Heck, Ted, I even have friends with saildrives!!!

from looking at the pic ....that is a good looking installation..neat and clean

Stu Jackson · Mar 5, 2015

woodster said:
from looking at the pic ....that is a good looking installation..neat and clean

Yes, woodster, it is.

But since boats are compromises, one has to understand the unforeseen consequences. If you look carefully, you'll see the engine is backwards. That means the alternator and belt and most likely the water pumps are at the rear of the engine. I don't know if there is a removable panel at the aft end, but changing a belt would be fun without one, wouldn't it? So, it's not ONLY the saildrive, it's what happens when one is employed that also counts.

Kings Gambit · Mar 5, 2015

Ted said:
I was speaking with a couple of insurance companies specifically about the diaphragm and was told that they would not insure a boat if the diaphragm is more than 7 years old. The boat I'm looking at has the original diaphragm which is 14 years old. The boat is uninsurable in it's present condition even though the diaphragm may not be leaking. Unless the seller is willing to replace it, I'm walking away form the deal.

My Bavaria is 16 yr old with the original diaphrams, which have never leaked. The thought of replacing them as matter of preventative maintenance is scarier to me than leaving them alone. It's a matter of original factory installation versus secondary installation by a "certified Yanmar mechanic", if you know what I mean

. It's almost like having that heart valve operation ahead of time (i.e., not leaking; not threatening to) because, statistically speaking, the valve has a 0.615 probability of failing this year given your age and medical history

. Or, more commonly-- "if it ain't broke, don't fix it." My insurance company (BOAT US) has not contacted me about a survey or any issues with the saildrive or the boat itself. If the diaphrams burst, tore, or otherwise started leaking and the boat sank and I tried to recover damages, I don't know what I might face if it was decided that the failure was b/c I had not replaced the diaphrams according to the manufacturer's "schedule." Sounds like potential litigation in the making.

woodster · Mar 5, 2015

Stu Jackson said:
Yes, woodster, it is.

But since boats are compromises, one has to understand the unforeseen consequences. If you look carefully, you'll see the engine is backwards. That means the alternator and belt and most likely the water pumps are at the rear of the engine. I don't know if there is a removable panel at the aft end, but changing a belt would be fun without one, wouldn't it? So, it's not ONLY the saildrive, it's what happens when one is employed that also counts.

you are correct in all that you stated......i don't know if i would like one or not...but the best place is to put them in million dollar yachts because anyone that can own one also has his maintenance man do his work

uncledom · Mar 5, 2015

I think I'm just not fond of having a huge chunk of aluminum which is attached to my main ground point hanging in the water all the time. I don't really like the fluid change issue either. I'll keep my stainless shaft with a dripless and cutlass.

JK_Boston_Catalina310 · Mar 5, 2015

Kings Gambit said:
My Bavaria is 16 yr old with the original diaphrams, which have never leaked. The thought of replacing them as matter of preventative maintenance is scarier to me than leaving them alone. It's a matter of original factory installation versus secondary installation by a "certified Yanmar mechanic", if you know what I mean. It's almost like having that heart valve operation ahead of time (i.e., not leaking; not threatening to) because, statistically speaking, the valve has a 0.615 probability of failing this year given your age and medical history. Or, more commonly-- "if it ain't broke, don't fix it." My insurance company (BOAT US) has not contacted me about a survey or any issues with the saildrive or the boat itself. If the diaphrams burst, tore, or otherwise started leaking and the boat sank and I tried to recover damages, I don't know I might face if it was decided that the failure was b/c I had not replaced the diaphrams according to the manufacturer's "schedule." Sounds potential litigation in the making.

This sounds like a primary reasons to not have a saildrive. If I can't reliably maintain a boat system myself I shouldn't have it. I can restuff a packing box, replace a packing box, replace my PSS dripless, etc.

Also, ignoring a preventive maintenance item that could allow water to flood your boat? Not for me.

My personal loathing of saildrives has been an issue. I would like to move onto a catamaran someday but almost all of the affordable ones have saildrives.

And the one time I skippered a saildrive boat my loathing proved true. We chartered a less than 1 year old Jenny in the BVIs. On the second day the saildrive wouldn't go into forward. Of course this happened just after we rounded a reef and dropped the sails at Marina Cay. Ended up backing down through the moored boats until we could get to an open mooring. People were looking at us like we were crazy. When the mechanics came out they confirmed what I had suspected, the saildrive was junk. They had an extra transmission with them so they could have swapped it out but with the saildrive they had to haul the boat. Boat was in charter for 9 months and this was in November so most of that time it sat unused because it was hurricane season. We were only the 6-7 group to charter that boat.

Anecdotal but I just can't get over my dislike for saildrives.

Fair winds,

Jesse

Ted · Mar 5, 2015

Boats can be fitted with a saildrive with the engine facing forward or backwards. Most of the installations that I have seen are installed with the drive leg aft. Stu's photo shows the drive leg in the forward position. Can't really tell if the opposite end is accessible but hope it would be. On installations with the drive leg aft, the companionway steps fold up or are removable to access the front of the engine like most conventional installations. The rear of the engine and drive leg are sometimes covered with a removable cover so access from both ends is possible. There is really no difference in accessibility when installed with the engine facing forward. The issue is not with the saildrive. The decision to install a saildrive backwards was made by the boat designer and how it fit into the overall cabin layout. Just another option available to the designer. Sort of like the "V" drive arrangements some boats have.

Ron20324 · Mar 5, 2015

Bad Obsession said:
... I wish that the manufacturers would stick with what works better for the long time. ....

Well, how many centuries passed before sailboats even had engines???

Sprega · Mar 5, 2015

I had a boat for many years that had a sail drive. I liked it. It still had the original diaphragm when I finely sold it. One nice thing about sail drives is the reduction of vibration that is transferred to the hull. My boat had a single cylender Volvo and there was no more noticeable vibration then there is with my current three cylender Universal with its conventional shaft and strut. I hauled my boat every three years. That is when the drive unit saw its maintainance. The boat motored very well both forward and backing. It Had a folding prop which I'm sure helped the boat to consistently out sail larger boats. I have never heard of a sail drive being the cause of a boat sinking. I would not hesitate to buy another boat with one.

Popularity of Saildrives

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