Surface drives - retrofit?

rbcoomer

rbcoomer

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Ok, probably going to be certified for this, but here goes anyway... :rolleyes:

As many will be aware already, I'm rebuilding an early Fletcher Arrowbolt - slow progress due to work, funds etc, but still moving on slowly. (I will update that thread soon :p ) Much of reason for doing was to learn some new skills and for the knowledge gained in doing in the first instance. The project is shortly going to get a cash injection to push forward and part of this will be used to replace the 5.0 V8 with a 5.7. This will yield a few extra horses and has focused attention to the ageing Alpha One drive. Whilst I don't believe there are any issues with this, it's going to be marginal on HP so that got me thinking about alternatives...

As I've replaced the transom and not yet cut out for the drive, I have a blank canvas and that started me thinking about surface drives! Whilst a new Arneson setup is a bit excessive on a cost basis, I started wondering about used and other types of surface drive - Levi, SeaFury, SDS, Q-SPD etc. Pricing data seems quite elusive, but I'm guessing if I need to ask, it will be eye-watering! I did find an entry level Arneson used in the US for $7500, but aside of the cost, shipping a pallet from the US won't be cheap either. I wondered if anyone had done anything similar and was willing to share experiences - good/bad?

Thanks :)
 
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If I were to go this route, I would be tempted to KIS... ie', not an articulated drive (Arneson etc., due to the complexity of the hydraulics... and price), but a simple straight shaft ... and there should be some nice packages out there.... http://www.q-spd.com/

You don't use the articulated drive fro boat trim anyway and to keep good steering is achievable with rudders...

Remember that surface drives gives significant lift to stern, so you need to seep some pro advise...
 
rbcoomer said:
I wondered if anyone had done anything similar and was willing to share experiences - good/bad?
Click to expand...
Never done that, but the answer to your good/bad question is bound to be the latter.
A single surface transmission on a 21' boat is a recipe for nightmare maneuverability.
Just to give an idea, at maneuvering speed you should expect to barely be able to steer on the prop walk side while going forward, and wherever the wind pushes you while reversing - I kid you not, it's that bad!
And as also DM1 said, a hull designed for a trimmable transmission is likely to not benefit at all from a surface prop on shaft.
If you are aiming for higher speed (as the move from the 5.0 to 5.7 block suggests), I'd rather consider a big outboard. A great combo for the Fletcher would be a Mercury Racing 2.5 EFI - the glorious 2 stroke engine whose revving limit is the sky...! :cool:
You need a bit of luck in finding a good used one though, because I don't think it's produced anymore.
Good luck anyway, whatever repowering you will go for.
Looking forward to your updates! :encouragement:
 
Divemaster1 said:
If I were to go this route, I would be tempted to KIS... ie', not an articulated drive (Arneson etc., due to the complexity of the hydraulics... and price), but a simple straight shaft ... and there should be some nice packages out there.... http://www.q-spd.com/

You don't use the articulated drive fro boat trim anyway and to keep good steering is achievable with rudders...

Remember that surface drives gives significant lift to stern, so you need to seep some pro advise...
Click to expand...

Thanks Alf - I'll take that as a sanity check! :encouragement:

I think cost of new and availability of used will likely put the brakes on the idea, but in terms of efficiency and simplicity, I'd like to investigate a bit further and will make some more enquiries as you never know what these things turn up sometimes.

I agree that the Q-SPD looks interesting, but it might not when I know the price! I have given a little consideration to stern lift. I'm adding some extra weight to the stern by means of a diesel heater and associated small tank, separate domestic battery and also a radar arch which will be just forward of the engine, so there are already a lot of unknowns. These are all being designed to be removable, so I'll have some scope for balancing, but envisaged that I'd need some forward weight and prop with some lift for the Alpha drive anyway. Transom angle also looks to be an issue with some types (and a factor in reversing the boat with surface drives), but my fibreglass skills have improved significantly. The hull needs painting anyway so back to the blank canvas in terms of fabricating a pod of some form below the swim platform (also still to be remade) if necessary. The other important factor might be engine positioning, as although I've not yet refitted engine bearers etc, scope to move forward (e.g. for an internal gearbox etc) is limited by bulkhead, fuel tank, rear seat etc. Only the bulkhead is fitted at the moment (and could still be moved), but overall vessel LOA at 21'4" would limit significantly.

Unfortunately, I have a bit of inner 'mad scientist' and not in a hurry so challenges like this have enormous appeal - a bit of an Achilles heel! :rolleyes:

Cheers,

Robin
 
MapisM said:
Never done that, but the answer to your good/bad question is bound to be the latter.
A single surface transmission on a 21' boat is a recipe for nightmare maneuverability.
Just to give an idea, at maneuvering speed you should expect to barely be able to steer on the prop walk side while going forward, and wherever the wind pushes you while reversing - I kid you not, it's that bad!
And as also DM1 said, a hull designed for a trimmable transmission is likely to not benefit at all from a surface prop on shaft.
If you are aiming for higher speed (as the move from the 5.0 to 5.7 block suggests), I'd rather consider a big outboard. A great combo for the Fletcher would be a Mercury Racing 2.5 EFI - the glorious 2 stroke engine whose revving limit is the sky...! :cool:
You need a bit of luck in finding a good used one though, because I don't think it's produced anymore.
Good luck anyway, whatever repowering you will go for.
Looking forward to your updates! :encouragement:
Click to expand...

Ah, a sanity check! :D

I'll ponder that whilst I go and do some work on the little Fletcher... (Other project - just moved the tank to the bow to improve balance.)

I have read about and understood the issues around reverse etc, but perhaps not appreciated 'how bad', so thanks. (Just that mad inner scientist to convince now :D )

P.S. not all about speed, the efficiency of the hull/fuel etc were main driving factors. Looking at a repower engine and the 5.7 is the same cost as a 5.0, so hence the power jump.
 
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Ok MapisM, I've had another look and some further thoughts on the low speed manoeuvrability... :)

How much would the rudder 'cowl' in the Levi design (e.g. http://www.levidrives.com/index.php/drive-type-secection/ld-240-250 ) alleviate prop-walk issue in your opinion? (I'm guessing not-a-lot?) This looks to be a fairly simple design and relatively straightforward to implement (aside of squeezing a reduction gearbox inside the boat).

I could add stern/bow thrusters to compensate for lost low speed manoeuvrability, but does seem counter-productive from a cost perspective!

Getting back to the directional thrust I fear... :nonchalance:

Outboard not really an option on a fuel cost basis as well as swim platform. I have a friend who has a couple of the Merc race engines - one on a 17' Fletcher! I gather they need a rebuild quite often once you start running 7K and above - sounds expensive! Also not really looking for a raceboat (although 50kts+ would be interesting!), more something a bit different/challenging to put together and as efficient as I can get it without going to diesel/turbocharged etc. I'm probably going to have spent 15K by the time I've finished, so 2-3K on a drive would be ok (ish) - but not another 10... I thought that if I'm going to have to look for s/h Bravo etc then a surface drive might be an interesting variation/alternative.

Perhaps I should stick with the Alpha One and lay off the throttle, but that sounds like a cop-out somehow! ;)
 
Have you thought about jet drive. Not sure if you could get the engine far enough forward but a jet fletcher would be awesome!! :)
 
RobWales said:
Used to own a Bayliner 2556 which had a 5.7 V8 running through an alpha one which was a factory fit, no worries with that engine and drive combination.
Click to expand...

Repower quote 300hp, the Alpha One Gen II is rated for 300hp from what I can see, but mine looks quite old... It's what I'll probably stick with, but just wanted to explore the options and the extra efficiency/speed caught my interest! I can't see that I'd be able to source anything for the cost of a new Alpha One, Gen II however, but hence the question if anyone had done similar - especially given the hostility from some quarters towards stern drives. Not that I share this view, and I think they are quite suited to many sub 30' sports boats. (I've also seen the costs of replacing cutless bearings, p-brackets, shaft seals etc, so even shafts aren't the holy grail! ;) )
 
rbcoomer said:
(I've also seen the costs of replacing cutless bearings, p-brackets, shaft seals etc, so even shafts aren't the holy grail! ;) )
Click to expand...

Ah but those are crazy marina prices where all the staff have to be paid..............:encouragement::encouragement::encouragement:
 
rbcoomer said:
I'm probably going to have spent 15K by the time I've finished
Click to expand...

For that budget you could get a brand new 300hp outboard, weighing just 240 kgs, and a hydraulic jack plate. You'd need transom mods of course, but it sounds like you could do those yourself. Fuel burn would be no worse than a petrol inboard and strendrive, maybe better.
 
rbcoomer said:
Outboard not really an option on a fuel cost basis as well as swim platform.
Click to expand...

but a mincemeater of a propeller protruding down there and under the bathing platform is okay on a 17 footer??

:p

Jet would be nice :D
rooster tail would be nicer :D

Genuine Q, shouldn't you have a properly designed hull at the aft section for either of them to work?

cheers

V.

PS. waiting for the thread update, last one must have been two years ago after some floods or something :p
 
RobWales said:
They all look old after 6 months submerged...... :-)
Click to expand...

True! :D

longjohnsilver said:
You're mad :):):)
Click to expand...

Yes :encouragement:

longjohnsilver said:
Ah but those are crazy marina prices where all the staff have to be paid..............:encouragement::encouragement::encouragement:
Click to expand...

No comment! ;)

Nick_H said:
For that budget you could get a brand new 300hp outboard, weighing just 240 kgs, and a hydraulic jack plate. You'd need transom mods of course, but it sounds like you could do those yourself. Fuel burn would be no worse than a petrol inboard and strendrive, maybe better.
Click to expand...

That's the whole boat budget including boat, trailer, quite a lot of timber and resin etc... :D

vas said:
but a mincemeater of a propeller protruding down there and under the bathing platform is okay on a 17 footer??

:p

Jet would be nice :D
rooster tail would be nicer :D

Genuine Q, shouldn't you have a properly designed hull at the aft section for either of them to work?

cheers

V.

PS. waiting for the thread update, last one must have been two years ago after some floods or something :p
Click to expand...

I only meant that the lack of a splash well and presence of a swim platform makes fitting an outboard tricky. I could loose the swim deck and fit a jack-plate, but a decent outboard 250-300hp would cost more than a new V8 (even with staff discounts LJS ;) )

Rooster tail... hrmm, yes - now that you mention I think my budget just went up a few percent... :p

Yes and no on the stern design - there's quite a bit of info out on the web (some probably best taken with a pinch of salt), but some of the surface drives have been designed to replace standard outdrive. I accept the benefit for some stern lift for reverse, but would probably look to directional drive units due to points illustrated by MapisM. (Appreciate that this adds cost, an articulation point and complexity)

Thread update on my list, not a huge amount of progress, but some. Lots of other priorities, career change and fiscal squeeze all impacted...

Thanks for all the input - not going to do anything hasty, but will keep looking! I quite like the Saro STP-300 SXR, but not the price tag - inevitable I guess as far less volume than the Volvo's and Mercruiser kit. :cool:
 
Fit the 5.7 litre and stick with the outdrive. Surface drive refit wI'll be a nightmare, you would need to consider, transom angle, if fixed drive the running angle of boat which would be trial and error as it is a one off, off set transom position due to the torque of single surface drive(my race boat need two inch offset) , inability to maintain slower speeds on plane , even big v8's struggle with torque on surface drives at slow speed when prop fully submerged, if considering trim able drive like arnesons then hydraulic trim and steering packs need to be considered .... Stick with the outdrive..
 
XPS said:
Fit the 5.7 litre and stick with the outdrive. Surface drive refit wI'll be a nightmare, you would need to consider, transom angle, if fixed drive the running angle of boat which would be trial and error as it is a one off, off set transom position due to the torque of single surface drive(my race boat need two inch offset) , inability to maintain slower speeds on plane , even big v8's struggle with torque on surface drives at slow speed when prop fully submerged, if considering trim able drive like arnesons then hydraulic trim and steering packs need to be considered .... Stick with the outdrive..
Click to expand...


That's far too sensible! But thanks - I think you're right :encouragement:
 
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