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Thread: Sailing catamaran auxilary propulsion

  1. #1

    Default Sailing catamaran auxilary propulsion

    Hi,

    As most of you know, I am looking for a smaller sized cat (limited by my budget) for extended cruising...

    We all would like to use the wind our sails all the time but we know this is not possible, therefore most of us have some kind of auxilary propulsion installed...
    In looking at so many boats available I did notice a lot of different setups, I guess all have their pro's and con's...

    But let me throw in here some thoughts, feel free to comment/add info etc to this... It might just help me in selecting a boat with a suitable propulsion system...

    Let me list what I have seen so far and added thanks to comments (on cats < 40ft) :


    1. Single outboard
    2. Dual outboards
    3. Single inboard with a steerable drive leg
    4. Single inboard on saildrive or propshaft in one hull
    5. Single inboard on saildrive or propshaft in one hull assisted by outboard next to opposite hull
    6. Single inboard powering hydraulic motors on dual saildrives or propshafts
    7. Dual inboards on saildrives or propshafts
    8. Dual electric motor on saildrives or propshafts
    9. Dual e-pod mounted under the hulls
    10. Hybrid systems


    I have not seen any gasoline inboard yet on a cruising mutihull, I guess they are around but I would never opt for this...

    A plus on the inboard engines mentioned in the thread is that they can be equipped with large alternators to supply electric power while motoring. They can also be used to produce hot water, so you can take your shower while motoring...

    I did see diesel outboards (did not list initially but adding this for completeness ;-). I was told Yanmar stopped production of these but it seems they are still available, long lasting and fuel efficient, however they seem to cost a furtune and will sink a dinghy (110 kg for the 27HP), therefore not so easy to lift off and carry to a shop in case of failure either.

    My ideas on the above listed setups :

    1 - Single outboard - Most economical setup (at installation), gasoline is more expensive than diesel, gasoline fumes can ignite, easy maintenance, in case of failure lift it off and take it to a shop, steering through rudder linkage, can be lifted to reduce drag, not a big electric power producer (only small alternators possible) ++ depending on the boat, steering can be more efficient with a steerable outboard compared to dual outboards ++

    2 - Dual outboards - Also economic setup, do not need to be linked to the rudders is mounted next to the hulls, steering through rpm variance or even one fwd and the other reverse, gasoline is more expensive than diesel, gasoline fumes can ignite, easy maintenance, in case of engine failure lift it off and take it to a shop, can be lifted to reduce drag, redundancy through dual engines, not a big electric power producer (only small alternators possible)

    3 - Single inboard / steerable leg - Probably most economic diesel setup, hydraulic steering of the drive leg adds complexity, hydraulic circuits and pumps, diesel is less expensive than gasoline, leg can be lifted to reduce drag

    4 - Single inboard in hull on saildrive or propshaft - not as heavy as dual setup, not sure about how weight has to be balanced, no engine maneuverability capability at all so bad for tight docking or anchoring situations

    5 - Single inboard in hull on saildrive or propshaft assisted by outboard next to opposite hull - as above but maneuverability problems solved by the outboard, economical solution (gasoline outboard only required when maneuvering) , redundancy through dual engines, accessibility to diesel engine, shaft/saildrives sometimes troublesome.

    6 - Single inboard hydraulic on dual saildrives or propshafts - steering through prop rpm variance or even one fwd and the other reverse, hydraulic circuits & motors, accessibility to hydraulic motors and saldrives sometimes troublesome

    7 - Dual inboards / saildrives or propshafts - steering through prop rpm variance or even one fwd and the other reverse, redundancy through dual engines, heaviest setup of all, smaller cats tend to be impacted by this weight located far aft (dramatically reducing load carrying capabilities of the whole boat), accessibility to engines, shaft/saildrives sometimes troublesome

    8 - Dual electric motor / saildrives or propshafts - larger battery bank (and space/weight) required - can be powered through generator for longer trips - batteries can be recharged through 'natural' sources, solar, wind, even props under sail (= drag), silent propulsion (as long as there is no need for long trips and the generator is required to power the engines)

    9 - Dual e-pods - no inside space required for motors, larger battery bank (and space/weight) required - can be powered through generator for longer trips - batteries can be recharged through 'natural' sources, solar, wind, even props under sail (= drag), silent propulsion (as long as there is no need for long trips and the generator is required to power the engines)

    10 - Hybrid systems - Same as options 8 and 9 but with minimal battery capacity thus saving space and weight, apart from short (timewise) maneuvering (docking/anchoring) the generator will supply power for motoring purposes.

    I suppose on a smaller boat the heaviest setups are to be avoided, the gasoline outboards have the advantage only one type of fuel is to be carried onboard since most of us carry a dinghy with an outboard.

    On this, I have already seen a few dinghies with small electric outboards and these seem to do very well so a boat carrying only diesel could charge the batteries for the electric dinghy and as such avoid the need for gasoline...

    There you go, most stuff we all know but I had a few spare moments

  2. #2

    Default Re: Sailing catamaran auxilary propulsion

    Quote Originally Posted by notly1988 View Post
    Hi,

    As most of you know, I am looking for a smaller sized cat (limited by my budget) for extended cruising...

    We all would like to use the wind our sails all the time but we know this is not possible, therefore most of us have some kind of auxilary propulsion installed...
    In looking at so many boats available I did notice a lot of different setups, I guess all have their pro's and con's...

    But let me throw in here some thoughts, feel free to comment/add info etc to this... It might just help me in selecting a boat with a suitable propulsion system...

    Let me list what I have seen so far and added thanks to comments (on cats < 40ft) :


    1. Single outboard
    2. Dual outboards
    3. Single inboard with a steerable drive leg
    4. Single inboard on saildrive or propshaft in one hull
    5. Single inboard on saildrive or propshaft in one hull assisted by outboard next to opposite hull
    6. Single inboard powering hydraulic motors on dual saildrives or propshafts
    7. Dual inboards on saildrives or propshafts
    8. Dual electric motor on saildrives or propshafts
    9. Dual e-pod mounted under the hulls
    10. Hybrid systems


    I have not seen any gasoline inboard yet on a cruising mutihull, I guess they are around but I would never opt for this...
    I had 2 x 2 stoke 16hp inboards with shafts on our 44ft cat. Perfect, maintenance was almost zero, a couple of spark plugs and a new air filter every year, no oil of oil filter changes, they would sustain 4.5 - 5 knots on one engine, very very light 50kg per side including transmission. Fuel was never a problem could even be started by hand. Unfortunately, the stupid eco regs (I used 3000ltrs in 10 years of cruising) prevented forward manufacture and spare parts. Also I installed the propellers too close to the surface so thrust was limited in rough waves when trying to moor or anchor. I now have diesel sail drives which use more fuel and are an expensive maintenance nightmare by comparison. OK rant over.


    A plus on the inboard engines mentioned in the thread is that they can be equipped with large alternators to supply electric power while motoring. They can also be used to produce hot water, so you can take your shower while motoring...

    I did see diesel outboards (did not list initially but adding this for completeness ;-). I was told Yanmar stopped production of these but it seems they are still available, long lasting and fuel efficient, however they seem to cost a furtune and will sink a dinghy (110 kg for the 27HP), therefore not so easy to lift off and carry to a shop in case of failure either.

    My ideas on the above listed setups :

    1 - Single outboard - Most economical setup (at installation), gasoline is more expensive than diesel, gasoline fumes can ignite, easy maintenance, in case of failure lift it off and take it to a shop, steering through rudder linkage, can be lifted to reduce drag, not a big electric power producer (only small alternators possible) ++ depending on the boat, steering can be more efficient with a steerable outboard compared to dual outboards ++
    This is the least expensive and lightest option. The amount you will spend on fuel will be minimised because of the low weight. Getting into harbours and slips in marinas can be very challenging, stopping is the hardest bit. Duel engines are much better at steering.

    2 - Dual outboards - Also economic setup, do not need to be linked to the rudders is mounted next to the hulls, steering through rpm variance or even one fwd and the other reverse, gasoline is more expensive than diesel, gasoline fumes can ignite, easy maintenance, in case of engine failure lift it off and take it to a shop, can be lifted to reduce drag, redundancy through dual engines, not a big electric power producer (only small alternators possible).
    Dual outboards have the added advantage of keeping the props out of the water when not used, permanently immersed propellers are expensive (folding/feather) and/or time consuming to keep from being fouled. They also don't require such regular anode changes if at all. Check the prices of shaft and leg anodes.

    3 - Single inboard / steerable leg - Probably most economic diesel setup, hydraulic steering of the drive leg adds complexity, hydraulic circuits and pumps, diesel is less expensive than gasoline, leg can be lifted to reduce drag
    Terrible

    4 - Single inboard in hull on saildrive or propshaft - not as heavy as dual setup, not sure about how weight has to be balanced, no engine maneuverability capability at all so bad for tight docking or anchoring situations
    Terrible

    5 - Single inboard in hull on saildrive or propshaft assisted by outboard next to opposite hull - as above but maneuverability problems solved by the outboard, economical solution (gasoline outboard only required when maneuvering) , redundancy through dual engines, accessibility to diesel engine, shaft/saildrives sometimes troublesome.
    Terrible, the worst of all things

    6 - Single inboard hydraulic on dual saildrives or propshafts - steering through prop rpm variance or even one fwd and the other reverse, hydraulic circuits & motors, accessibility to hydraulic motors and saldrives sometimes troublesome
    Terrible, noise, ineffeceint, lots of maintenance no redundancy, heavy

    7 - Dual inboards / saildrives or propshafts - steering through prop rpm variance or even one fwd and the other reverse, redundancy through dual engines, heaviest setup of all, smaller cats tend to be impacted by this weight located far aft (dramatically reducing load carrying capabilities of the whole boat), accessibility to engines, shaft/saildrives sometimes troublesome
    You have pretty much nailed it, you do get a hot shower when you arrive somewhere. Sail drives are much more trouble than shafts

    8 - Dual electric motor / saildrives or propshafts - larger battery bank (and space/weight) required - can be powered through generator for longer trips - batteries can be recharged through 'natural' sources, solar, wind, even props under sail (= drag), silent propulsion (as long as there is no need for long trips and the generator is required to power the engines)
    You have pretty much nailed it, batteries are either very expensive or heavy, sail drives are much more trouble than shafts

    9 - Dual e-pods - no inside space required for motors, larger battery bank (and space/weight) required - can be powered through generator for longer trips - batteries can be recharged through 'natural' sources, solar, wind, even props under sail (= drag), silent propulsion (as long as there is no need for long trips and the generator is required to power the engines)
    You have pretty much nailed it, batteries are either very expensive or heavy. The whole set up is expensive.

    10 - Hybrid systems - Same as options 8 and 9 but with minimal battery capacity thus saving space and weight, apart from short (timewise) maneuvering (docking/anchoring) the generator will supply power for motoring purposes.
    These systems are very expensive lots of electronic controllers not very reliable

    I suppose on a smaller boat the heaviest setups are to be avoided, the gasoline outboards have the advantage only one type of fuel is to be carried onboard since most of us carry a dinghy with an outboard.
    Answered you own question 2 x 9.9 Yamaha high thrust outboards

    On this, I have already seen a few dinghies with small electric outboards and these seem to do very well so a boat carrying only diesel could charge the batteries for the electric dinghy and as such avoid the need for gasoline...
    Unless you are OCD about charging it will always be flat when you most need it. Rigid rowing dinghy, with sailing rig???

    There you go, most stuff we all know but I had a few spare moments
    Petrol should be treated with respect but it is less dangerous than gas (butane/propane) most boats cook with gas. Using propulsion engines to charge is wasteful and increases the maintenance, fit solar and perhaps a standalone petrol generator for the odd time you might need it (battery charging, angle grinder on the beach etc)

    Assuming your limited budget will mean second hand boats then these choices will many be determined by what is available. I once had a friend that had a petrol power boat and was planning to convert to diesel, based on his usage it would have taken close to 75 years to break even. You really don't use much fuel on a catamaran and even less on one that sails well.
    Last edited by Peter; 9th August 2018 at 02:13 PM.

  3. #3

    Default Re: Sailing catamaran auxilary propulsion

    Some of the latest Honda outboards have charging facilities.

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