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Old 10-04-2020, 09:00   #1
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Converting from shaft drive to sail drive - Questions

Hey all,

I am not looking to do this right now - I just wanted a video of a popular youtube channel where they converted from shaft to saildrive in an effect to get their electric system more efficient and this got me thinking.

As some of you know I am a full time live aboard, working on rebuilding/setting up for cruising while saving up and awaiting for my now hopeful stock option pay out in 2 years before I head out cruising. Goal is to cruise from PNW down the coast to Baja, do a bit of cruising in Sea of Cortez then make the jump over to the south pacific and from there who knows.

That being said, our boat is a fairly heavy boat - 42ft and last haul out prior to moving aboard and being loaded was weighing in @ 36,000 lbs. In reverse she has really terrible prop walk to starboard - we have to goose it out of the slip for the first 30 feet or so before the rudder kicks in.

The other thing is that our engine is using a V drive transmission. The shaft comes in through the boat right under the engine and as such, visually we can not see our shaft or shaft seal - major concern of mine since you can't monitor its state.

That being said, after watching their conversion video I started thinking about it. THe biggest pro for me IMO would be the fact that the engine can be rotated to face forward and that the shaft doesn't live under the engine where i can't inspect it.

Does anyone have any opinions on this conversion? Has anyone personally done it? What was the experience like?

PROS:
- Engine can face forward - no longer have to climb through small access holes to just work on something like the alternator
- No longer have the worry about alignment issues
- Shaft seal is removed(though replaced with something else)
- Sail drive is inspectable
- Future wise can upgrade to all electric and gain regen
- Engine MAY be able to move aft - giving more working room
- Prop walk reduced or gone

CONS:
- PITA to service in far away locations
- Requires haulout for oil changes
- Stray current causes corrosion
- Obviously things I am not thinking of


PS my engine is a Yanmar 4JH2-UTE - 100hp turbo.
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Old 10-04-2020, 09:51   #2
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Re: Converting from shaft drive to sail drive - Questions

"- Obviously things I am not thinking of"

It might be a good plan, but I've had bad experiences with similar bright ideas of mine, and it's usually in the area of solving the problem I was trying to solve but taking on new problems I didn't think of.

The job is going to require remounting the engine, as well as changing everything from the throttle cable to the cooling system.

You are going to do some major surgery on the midline of your boat, which is rather important structurally.

Past posts have bemoaned all the lobster pots that are attracted to sail drives.

Sail drive means two 90 degree gears in your drive train rather than one.

Again, it might be a good idea; the pros may outweigh the cons. Perhaps your calculation should include ways to mitigate the cons of your current arrangement, such as a camera on a stick or fins and a mask. Consider pulling maintenance on your shaft before a long trip, such that you don't have to worry about it.

My late father-in-law, a Panama Canal pilot, rebutted my complaint that my boat is hard to steer in reverse by saying that the only ship he had ever been able to steer in reverse was a three prop destroyer.
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Old 10-04-2020, 12:28   #3
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Re: Converting from shaft drive to sail drive - Questions

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Originally Posted by tkeithlu View Post
"- Obviously things I am not thinking of"

It might be a good plan, but I've had bad experiences with similar bright ideas of mine, and it's usually in the area of solving the problem I was trying to solve but taking on new problems I didn't think of.

The job is going to require remounting the engine, as well as changing everything from the throttle cable to the cooling system.

You are going to do some major surgery on the midline of your boat, which is rather important structurally.

Past posts have bemoaned all the lobster pots that are attracted to sail drives.

Sail drive means two 90 degree gears in your drive train rather than one.

Again, it might be a good idea; the pros may outweigh the cons. Perhaps your calculation should include ways to mitigate the cons of your current arrangement, such as a camera on a stick or fins and a mask. Consider pulling maintenance on your shaft before a long trip, such that you don't have to worry about it.

My late father-in-law, a Panama Canal pilot, rebutted my complaint that my boat is hard to steer in reverse by saying that the only ship he had ever been able to steer in reverse was a three prop destroyer.

Thanks for that. I do agree that there are unknowns that would bring about pains. Its just a matter of which pains are worse.

I don't think i'd do the conversion unless all other projects are complete and I'm feeling the need to do another big one and have the capital I am wanting to burn - unlikely to happen.

That said, maybe someone will come out with some way to drive a externally mounted shaft/prop that wouldnt have a hole through the boat. Maybe some big ass magnet on the interior and exterior to rotate the prop.

Anyways, The question is definitely more curiousity than actual action. I really appreciate the comment and makes me realize that I too have found that this one statement "- Obviously things I am not thinking of" brings about headaches due to the unexpected nature of things.
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Old 10-04-2020, 14:36   #4
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Re: Converting from shaft drive to sail drive - Questions

YouTube has a video on that . look under "sailing UMA".
I just watched it last night.
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Old 10-04-2020, 18:35   #5
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Re: Converting from shaft drive to sail drive - Questions

The OP already stated that video was the inspiration of his question.
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Old 10-04-2020, 20:25   #6
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Re: Converting from shaft drive to sail drive - Questions

I have to agree with tkeithlu as I often find myself in the same position.

Sometimes you just have to rethink the problem. Do I try for better access or settle for easier implementation?

My previous boat had a number of very-hard-to-get-to items. One of the worst was the pump on my vacuum operated toilet. The solution was to make 6" long nuts out of hex brass bar to go on the hold down bolts (I have done this one with counter bores so that they slip over the bolt and align the threads for easy starting)

Similar problem with starter motor retaining nuts. By welding two nuts onto the ends of a piece of SS tubing about a foot long and running a tap through them I extended them out all the way to the front of the starter motor where they were easy to get at.

Plenty of little USB or Wifi TV cameras available today and the old torch and mirror trick still works well.

I think you are better off with the V drive than a sail drive, I just watched a guy pull off two props less than 12 months old which looked like mice had been chewing on them.
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Old 11-04-2020, 08:34   #7
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Re: Converting from shaft drive to sail drive - Questions

Stick with your shaft...the list of problems with saildrives is far greater...Ive converted my boat to a shaft after having a series of saildrives..
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Old 11-04-2020, 08:57   #8
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Re: Converting from shaft drive to sail drive - Questions

Another option would be to convert to diesel electric drive. This would allow you to move the engine to any position that gives access to the drive train, adds the possibility of a very controlled low power electric drive for maneuvering. It would probably be no less efficient than the V drive while avoiding cutting a large hole in the bottom of the boat. Putting in a sail drive is a major piece of engineering requiring stress calculation beyond most unless you are a structural engineer and if you get it wrong could substantially weaken the hull.
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Old 11-04-2020, 10:03   #9
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Re: Converting from shaft drive to sail drive - Questions

I have a V drive also. A Hurth 150V/ZF MI15V IIRC. To get access to the shaft seal pull the transmission off. It is actually pretty easy and it takes me about 45 minutes each way. With a PSS there is very little maintenance on the seal. If you have standard packing I could see this as a big PITA but for the PSS it is no big deal. I can see and touch the PSS, just can't take it apart without removing the transmission.

A saildrive requires a haulout to change the gear oil - an annual event which in my case would triple my haulouts. With all the other negatives of saildrives I would not want one.
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Old 11-04-2020, 10:23   #10
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Re: Converting from shaft drive to sail drive - Questions

I would never have a sail drive, I know all the new boats seem to have them, basically you have a big hole under your boat, you can plug a shaft hole, can't plug that giant hole for the shaft drive, seen it go gad many times
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Old 11-04-2020, 10:39   #11
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Re: Converting from shaft drive to sail drive - Questions

I would not have a saildrive period. The only reason they are now used so much on new production boats is because the are cheaper. Bad for long term ownership and agree totally with Mirelos
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Old 11-04-2020, 11:47   #12
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Re: Converting from shaft drive to sail drive - Questions

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I would never have a sail drive, I know all the new boats seem to have them, basically you have a big hole under your boat, you can plug a shaft hole, can't plug that giant hole for the shaft drive, seen it go gad many times

"seen it go bad many times"???? I personally have a saildrive, that I replaced the seal on after 25 years. It was as good as the new one. Flexible, no cracking, no cuts, no wear. Also have a handful of boater friends with saildrives that have had the same experience. VP recommends replacing the seal every 7 years, but obviously they are way over built and engineered, so I completely doubt your statement With a saildrive, I have no alignment issues, less vibration, no dripping water, better angle of attack, and test have proven they are more hydrodynamic than shaft drives. Change out the zincs once a year and you're good. The only negative I see is you need to haul the boat in order to have the saildrive/ transmission worked on. Yea, there's a big hole in the bottom of my boat, but there are a lot of holes in the bottom of my boat. BTW I was neither here nor there concerning saildrives before I had one. I had more problems and issues on boats with shaft drives than my saildrive. Would I go through the expense and time to replace a shaft with a saildrive? Probably not, but I wouldn't not buy a boat because it had one.
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Old 11-04-2020, 12:26   #13
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Re: Converting from shaft drive to sail drive - Questions

you hit a hard object with a shaft, you may bend your prop or shaft...sail home, haul out and repair...with a sail drive you hit a hard object and you'll be taking in gallons of water., friends and family that work on yards for first hand experience
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Old 11-04-2020, 12:40   #14
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Re: Converting from shaft drive to sail drive - Questions

Doesn't need to be a hard object. A few years ago a friend was following me down a flooded river. I noticed some branches caught on something and attempted to turn. It hit my keel and the boat rolled once and I was clear. He hit it with one of his sail drives, split the rubber boot and flooded his engine compartment. It was a rope across the river, used by net fishermen which normally lay on the bottom but which the current and fouled trees had lifted to the surface. They do make a nice compact installation though.
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Old 11-04-2020, 13:01   #15
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Re: Converting from shaft drive to sail drive - Questions

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Doesn't need to be a hard object. A few years ago a friend was following me down a flooded river. I noticed some branches caught on something and attempted to turn. It hit my keel and the boat rolled once and I was clear. He hit it with one of his sail drives, split the rubber boot and flooded his engine compartment. It was a rope across the river, used by net fishermen which normally lay on the bottom but which the current and fouled trees had lifted to the surface. They do make a nice compact installation though.

Don't see how he split a rubber boot without causing serious damage to his engine or saildrive. Both parts are bolted together and don't move independently. And it is rubber...
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