Saildrives vs Inboard

[Open-d]

I would like to discuss the issue of saildrives vs inboards. I am not a fan of saildrives as they appear to be weak and vulnerable. Further, they concentrate weight to the rear instead of centered.

However, they are popular.

Please discuss. Pros and Cons.

[Tin Tin]

So as we are in the multihull section of the forum, we are usually talking two engines. When we first looked at buying a cat in 2001 80% of them had the engine "indoors" ie. accessible under a bunk or cupboard. Those boats all smelled of old diesel/oil etc, were difficult to service etc. We ended up with outboards as my wife felt ill with that smell. Since then many cats had engines installed in the rear of the hulls behind a sealed wall. We bought one on those in our second cat and loved it. Easy to work on engines (and sail drives) , separate engine compartment, easy to keep clean and dry and free of muck. Also less noise and vibration.


Now of course this loads weight into the sterns, so they design the hulls with that in mind of course. If you are a sailing perfectionist and want the weight centered and use shaft drives then go for it, if you can find a modern cat like that now days.


Sail drives are surprisingly robust, usually hung behind protecting keel or skeg. The positives and negatives include but not limited to:


Positives:
1 Engine/SD can be lifted straight out, no manhandling through the saloon

2 Easy to service and keep clean
3 No internal odours
4 More efficient prop drive angle

5 No bent shaft, alignment, balancing, cutless bearing, dripping seal issues




Negatives:
1 Need more anti corrosion care underwater
2 Clutch wear in older models
3 Oil seal maintenance complicated - but may be so on shaft gear box too
4 Weight concentration at rear (although some old model cats have sail drives further forward in the middle of the hull sloped to one side - looks like a headache to work on)
5 Potential for catastrophic damage from mooring line wraps around prop where SD becomes unseated and breaks seal


......there maybe more

[StuM]

Do you mean
Saildrive v shaft drive
or

Outboard v inboard?

[Jammer]

Originally Posted by Open-d

Please discuss. Pros and Cons.

Short answer is that saildrives require more care, don't last as long, and are harder to repair when they fail. But they result in a boat with more usable space for the dollar spent initially, and have various minor benefits when new (or nearly so).



Pros

- Quieter
- Less vibration
- Somewhat more efficient
- Do not have the alignment problems that tend to plague inboard (direct) drives over their service life
- Generally offer more flexibility in engine placement to the boat designer and result in less wasted space


Cons

- More vulnerable to damage from floating and submerged debris and and obstacles. More likely to catch lines from e.g. lobster pots.
- More likely to require repairs that demand a haulout, notably seal failures and gearcase/clutch failures. On an inboard these are less common and do not require a haulout to address
- Are more prone to failures that require specialized parts. It is not uncommon to replace the entire saildrive, which must then be ordered from the original manufacturer. In contrast most inboard problems involve standard parts that are available anywhere e.g. cutless, shaft log and packing, shaft.
- Typically require replacement of the boot roughly every 10 years, which requires removal of the saildrive and engine.
- Prone to failures due to grounding and stray current problems. In theory the risk can be mitigated through use of isolation transformers etc which perhaps are a good idea anyway. The fact remains that people who know what they are doing nonetheless experience saildrive corrosion failures due to stray current.

[boatpoker]

******

[Open-d]

Originally Posted by Tin Tin

So as we are in the multihull section of the forum, we are usually talking two engines. When we first looked at buying a cat in 2001 80% of them had the engine "indoors" ie. accessible under a bunk or cupboard. Those boats all smelled of old diesel/oil etc, were difficult to service etc. We ended up with outboards as my wife felt ill with that smell. Since then many cats had engines installed in the rear of the hulls behind a sealed wall. We bought one on those in our second cat and loved it. Easy to work on engines (and sail drives) , separate engine compartment, easy to keep clean and dry and free of muck. Also less noise and vibration.


Now of course this loads weight into the sterns, so they design the hulls with that in mind of course. If you are a sailing perfectionist and want the weight centered and use shaft drives then go for it, if you can find a modern cat like that now days.


Sail drives are surprisingly robust, usually hung behind protecting keel or skeg. The positives and negatives include but not limited to:


Positives:
1 Engine/SD can be lifted straight out, no manhandling through the saloon

2 Easy to service and keep clean
3 No internal odours
4 More efficient prop drive angle

5 No bent shaft, alignment, balancing, cutless bearing, dripping seal issues




Negatives:
1 Need more anti corrosion care underwater
2 Clutch wear in older models
3 Oil seal maintenance complicated - but may be so on shaft gear box too
4 Weight concentration at rear (although some old model cats have sail drives further forward in the middle of the hull sloped to one side - looks like a headache to work on)
5 Potential for catastrophic damage from mooring line wraps around prop where SD becomes unseated and breaks seal


......there maybe more

Thanks. I like the access for rear-engines with saildrive. Thanks.

[Open-d]

Originally Posted by StuM

Do you mean
Saildrive v shaft drive
or

Outboard v inboard?

The former.

[robert sailor]

Saildrives are popular with manufacturers because they are quite a bit cheaper and far easier to install with unskilled labor. Most knowledge purchasers prefer shaft drives even in Catamarans although very few manufacturers give them that option.

[Open-d]

Originally Posted by robert sailor

Saildrives are popular with manufacturers because they are quite a bit cheaper and far easier to install with unskilled labor. Most knowledge purchasers prefer shaft drives even in Catamarans although very few manufacturers give them that option.

Thanks.

[Tin Tin]

Originally Posted by robert sailor

Saildrives are popular with manufacturers because they are quite a bit cheaper and far easier to install with unskilled labor. Most knowledge purchasers prefer shaft drives even in Catamarans although very few manufacturers give them that option.

Why would a sail drive be less expensive than a simple shaft drive? Did a manufacturer tell you this?

[Chotu]

Originally Posted by Tin Tin

Why would a sail drive be less expensive than a simple shaft drive? Did a manufacturer tell you this?

Labor is the majority cost of building a boat.

It's cheaper to cut a hole and install a saildrive.

[warren2]

I have volvo saildrive and you cant attach a rope cutter - big problem

[mglonnro]

I think all new Gunboats and Outremers come with saildrives. To me, that is good evidence that the pros outweigh the cons.

[jmh2002]

I prefer the various retractable propulsion options

[a64pilot]

Originally Posted by mglonnro

I think all new Gunboats and Outremers come with saildrives. To me, that is good evidence that the pros outweigh the cons.

Pros for the manufacturer?
However one assumes if you can afford either new, then buying a replacement sail drive every few years is no big deal, plus I don’t believe many new boat buyers keep that boat for too many years.
Many buy new cause simply put they can afford it and trade up every few years like they do their car, cause they can afford it.

Shaft drive is cheaper to own and maintain, but if your buying a new Gunboat, that’s likely irrelevant.