Whitelighter
Well-Known Member
Ok ok so stern drives are harder than shafts.
Does that mean we agree I'm better at boat handling as well then
Does that mean we agree I'm better at boat handling as well then
Boat and engine efficiancy, drive type?
- Thread starter Robg71
- Start date
AdeOlly
Well-Known Member
I agree single outdrive boats at slow speed are a nightmare. Twins much better though. In a cross wind in a twin o/d it's easy enough to vary the revs so that the boat stays in a straight line.
To the OP - I'd be very wary about buying 15yr old outdrives. The Volvo drives of that vintage had a service life of 1000hrs before a rebuild was required. This was stated in the service manual....
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Deleted User YDKXO
Guest
I don't know about that. The Sealine S37 I once owned had twin outdrives and that wandered about just as badly as the single outdrive Searay I had a few years before that. I don't even think it's a wind issue. I just think that pushing a hull from the back rather than the middle is inherently unstable. Its like pushing a shopping trolley; they never go in a straight line
[2068]
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If you're wandering around all over the place at low speed with twin outdrives, they need adjusting!
>>The Volvo drives of that vintage had a service life of 1000hrs before a rebuild was required
Not many make it to 1000hrs without some sort of rebuild happening anyway: fishing line, damaged prop seals, etc. etc.
But then again, you can have gearbox gremlins, leaky glands, worn bearings, wonky shafts, etc. on shafts too.
Outdrives are fab if new or if they've been meticulously maintained.
General advantages of outdrives:
- If you hit something, they might kick up and stay waterproof
- Shallow water capability
- Better (faster, less fuel) at higher speeds (30kts +)
- Vectored thrust, if you know what you are doing
>>The Volvo drives of that vintage had a service life of 1000hrs before a rebuild was required
Not many make it to 1000hrs without some sort of rebuild happening anyway: fishing line, damaged prop seals, etc. etc.
But then again, you can have gearbox gremlins, leaky glands, worn bearings, wonky shafts, etc. on shafts too.
Outdrives are fab if new or if they've been meticulously maintained.
General advantages of outdrives:
- If you hit something, they might kick up and stay waterproof
- Shallow water capability
- Better (faster, less fuel) at higher speeds (30kts +)
- Vectored thrust, if you know what you are doing
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Deleted User YDKXO
Guest
The boat was almost brand new (ex dealer demo boat) and I did ask the dealer to check the alignment. He did do that but also said that they all do that, sir. But yes I suppose its possible the drives were out of alignment despite the dealer check but other outdrive powered boats I've had have exhibited the same tendency to the same or lesser degree. IMHO its a characteristic of the drive system
AdeOlly
Well-Known Member
I don't know about that. The Sealine S37 I once owned had twin outdrives and that wandered about just as badly as the single outdrive Searay I had a few years before that. I don't even think it's a wind issue. I just think that pushing a hull from the back rather than the middle is inherently unstable. Its like pushing a shopping trolley; they never go in a straight line
Hmm, well IMO it shouldn't have, as FP says it sounds like the drives on your old S37 were out of adjustment. On my Prestige as on my previous Seawings I can set up steering and throttle so that it goes in a straight line with only fairly minimal ongoing correction needed. I've had many, many hours practice at this trundling up and down Chi harbour! If there's a variable or gusty wind on the beam then more work is needed, and yes most likely more than would be needed on shafts. On my previous two single engine Sealines the steering input was continual at low speeds and a right pain. Anyway, I now have autopilot so have the option to cheat in this regard
[2068]
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No wandering on the current FP, which is a S28 with twin KAD32's.
Previous S24 on single KAD32 was all over the place.
Robg71
Well-Known Member
So, just out of curiosity, how much is a full overhaul, how much is a basic service on outdrives.
Is it something that can be done easily, does it need specialist tools.
At the moment, shafts are winning this, because the 20k difference in the boats i have been looking at is a lot of diesel.
Ok, i realise im not comparing like for like, but, i think for twenty plus year old boats, a lot are probably overpriced by a good way, and nothing is selling.
Is it something that can be done easily, does it need specialist tools.
At the moment, shafts are winning this, because the 20k difference in the boats i have been looking at is a lot of diesel.
Ok, i realise im not comparing like for like, but, i think for twenty plus year old boats, a lot are probably overpriced by a good way, and nothing is selling.
rafiki_
Well-Known Member
Rafiki is on twin outdrives, and while she is easy to handle, at displacement speeds, she is susseptible to the breeze. This is amplified when mooring, but if my alignment is wrong, I'll just go around again, and give it another go.
I don't think that shaft drive boats drive from the middle, as the props are at the stern, although not as far back as outdrives. The powertrain mass is more centralised, so the centre of mass is much further forward than on a sterndrive boat.
As for maintenance costs, the key is preventative maintenance, and Rafiki probably costs about £500 per year for the engines/drives, but I do some of the work myself. I think VP's are a bit more vulnerable to things like fishing line etc.
I don't think that shaft drive boats drive from the middle, as the props are at the stern, although not as far back as outdrives. The powertrain mass is more centralised, so the centre of mass is much further forward than on a sterndrive boat.
As for maintenance costs, the key is preventative maintenance, and Rafiki probably costs about £500 per year for the engines/drives, but I do some of the work myself. I think VP's are a bit more vulnerable to things like fishing line etc.
Scarron
Well-Known Member
You can handle outdrives fine if you practice!
Having just spent a few day in Venice idly watching the water taxi drivers practice their skills followed by a trip around the narrowest canals in a highly varnished all-wood one I am now convinced that I have nothing to fear in going from two to just one outdrive, it'll just take practice...
Their boat handling skills have to be seen to be belived, 30ish footers all on a single outdrive (more than 90% Volvo Duo-prop)
It can be done, and if you look after them with proper preventative maintenance they are reliable, (taxis here must do thousands of hours) and fuel burn will be at a minimum 70% of a shaft driven boat.
Same conclusion as always on here - It all depends how big a boat you want and how many hours you're realistically going to do.
Having just spent a few day in Venice idly watching the water taxi drivers practice their skills followed by a trip around the narrowest canals in a highly varnished all-wood one I am now convinced that I have nothing to fear in going from two to just one outdrive, it'll just take practice...
Their boat handling skills have to be seen to be belived, 30ish footers all on a single outdrive (more than 90% Volvo Duo-prop)
It can be done, and if you look after them with proper preventative maintenance they are reliable, (taxis here must do thousands of hours) and fuel burn will be at a minimum 70% of a shaft driven boat.
Same conclusion as always on here - It all depends how big a boat you want and how many hours you're realistically going to do.
gjgm
Well-Known Member
That assumes all goes well with servicing.
I had an outdrive explode (literally, through the casing). A new one isnt £500
rafiki_
Well-Known Member
That assumes all goes well with servicing.
I had an outdrive explode (literally, through the casing). A new one isnt £500
What was the root cause of the problem that resulted in the "explosion"?
tico
Well-Known Member
At a guess... no oil
I had an old VP290 sieze up when the top bearing siezed (no oil)
Took a while to rebuild it plus some clever engineering trickery but good as new after.
I had an old VP290 sieze up when the top bearing siezed (no oil)
Took a while to rebuild it plus some clever engineering trickery but good as new after.
[2068]
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Oh yes, shaftdrives are bomb proof, and new gearboxes are as cheap as chips, too ...
http://www.ybw.com/forums/showthread.php?t=324095
http://www.ybw.com/forums/showthread.php?t=324095
rosssavage
Well-Known Member
Outdrives transfer the thrust to the transom, hence rear drive. Shafts transfer the thrust (via the propshaft..) to the gearbox, and hence to the engines and via the engine mounts to the hull. In the middle.
volvopaul
Well-Known Member
The rough retail price of a Volvo dph drives is near on twice as much as it's equivalent gearbox in rated hp it can handle, plus the drive needs , far more servicing and eats anodes, and steering rams, which although there on now the 4th design they still leak am told.
epervier
Well-Known Member
Having had both types of drives, Sunseeker Portofino 31 with 290 dp and now with a Weymouth 32 on shafts, the shafts are a dawdle to use compared to the legs, but I can't make a useful comment as to economics as the two boats are worlds apart in hull design, I will add the current boat burns a lot less per hour than the previous one, but having said that, it max's out at less than half the speed of the seeker.
Portofino
Well-Known Member
When I took my boat ( outdrives) Sunseeker to the Med 7 years ago ,diesel was less than 80 cents now it's over € 1 . 50 , well nearly double / per L
My DPG legs have been serviced by VP agent ,no probs some 500 hrs clocked up
Fuel burn @ 27/28 knots cruise 60-70 L/ Hour that's 3000 rpm
@ 3200 then 30 knots and 75 L/ h On a pair of KAMD 300's Sterring ram is inside the boat , so no issues here.
Reading arrond the Forum generally fuel burn seems to be a bit of a taboo subject - think IPS that's 400 + Hp through a " leg " just connects to the engine in a different manor exits under the boat as opposed to the transom ,facing forward.I think they up to around 600 hp?
It fuel efficiency really folks
Driving well any fool can " learn" to drive/ park a boat ,car ,plane, heiicopter ,
Boats have bow thruster and some these days stern t,s and now we have the joy of Joyskicks - to park up .Driving issue today is a red herring
Think of your wallet @ 30 knots
My DPG legs have been serviced by VP agent ,no probs some 500 hrs clocked up
Fuel burn @ 27/28 knots cruise 60-70 L/ Hour that's 3000 rpm
@ 3200 then 30 knots and 75 L/ h On a pair of KAMD 300's Sterring ram is inside the boat , so no issues here.
Reading arrond the Forum generally fuel burn seems to be a bit of a taboo subject - think IPS that's 400 + Hp through a " leg " just connects to the engine in a different manor exits under the boat as opposed to the transom ,facing forward.I think they up to around 600 hp?
It fuel efficiency really folks
Driving well any fool can " learn" to drive/ park a boat ,car ,plane, heiicopter ,
Boats have bow thruster and some these days stern t,s and now we have the joy of Joyskicks - to park up .Driving issue today is a red herring
Think of your wallet @ 30 knots
baylabayla3288
Well-Known Member
When I compare my current Phantom 38 (twin TAMD 63p a' 370 hp on shafts) with my previous Princess 34 (twin kad 42, a' 230 on DP) it is like day and night difference in all aspects of handling in favour of the Phantom.
Surpricingly also the fuel consumption is better with the Phantom. I have just compleated 1000 NM this season so far and my average fuel consumption has been 3,9 l/NM (I cruise typically 20 to 24 knots with some 8 knots runs). With the Princess I did never get below 4, usually when loaded with fuel and holiday gear it was often more than 4,5. With the Phantom I measured a 50 nm run at 8 knots @ 1000 rpm where my fuel burn was 2 l/ NM (16 l/h). Adding to the economics I rebuilt both legs on the Princess at 900 hours due to water intrusion, gears missing, to much play, clutch slippage etc +3000€ per side.
I find it wery nice to have the full speed range usable, which is the case with the Phantom. With the princess, speeds between 8 - 18 were not usable due to the bow high attitude. At lower speeds a lot of steering was needed to keep the course. The large play in Volvo's power steering made things worse.
I must say that there are also many things in the Princess that were nice, for example no soot on the transom thanks to the exhaust exiting under water, super silent in the saloon due to engines aft and the slow speed course keeping problem was reduced if one tab was lowered. To be fair the princess was slightly underpowered and the Phantom ideally powered, this probably explains some of the fuel consuption issues. The princess topped 27 knots and the phantom tops 30 (both light), the Phantom accelerates much better and is less sensitive to load.
Some additional reasons to all this in general is that with shafts larger props (diameter) can be used that provides better allround performance at low and mid range speeds. Also because shaft engines are typically installed further apart relative to the beam of the boat and the props are more forward, closer to the pivot point, better low speed handling is a result. In addition larger wheels give a significant prop walk effect (I would not install a stern thruster) and shafts gives better longitudal wight balance (if not v drive).
My take on this is that if you use the boat for cruising mostly up to 25 knots and it is a relatively heavy deep v build, shafts are the way to go.
Sorry for the long post, hope it helps in the evaluation.
Surpricingly also the fuel consumption is better with the Phantom. I have just compleated 1000 NM this season so far and my average fuel consumption has been 3,9 l/NM (I cruise typically 20 to 24 knots with some 8 knots runs). With the Princess I did never get below 4, usually when loaded with fuel and holiday gear it was often more than 4,5. With the Phantom I measured a 50 nm run at 8 knots @ 1000 rpm where my fuel burn was 2 l/ NM (16 l/h). Adding to the economics I rebuilt both legs on the Princess at 900 hours due to water intrusion, gears missing, to much play, clutch slippage etc +3000€ per side.
I find it wery nice to have the full speed range usable, which is the case with the Phantom. With the princess, speeds between 8 - 18 were not usable due to the bow high attitude. At lower speeds a lot of steering was needed to keep the course. The large play in Volvo's power steering made things worse.
I must say that there are also many things in the Princess that were nice, for example no soot on the transom thanks to the exhaust exiting under water, super silent in the saloon due to engines aft and the slow speed course keeping problem was reduced if one tab was lowered. To be fair the princess was slightly underpowered and the Phantom ideally powered, this probably explains some of the fuel consuption issues. The princess topped 27 knots and the phantom tops 30 (both light), the Phantom accelerates much better and is less sensitive to load.
Some additional reasons to all this in general is that with shafts larger props (diameter) can be used that provides better allround performance at low and mid range speeds. Also because shaft engines are typically installed further apart relative to the beam of the boat and the props are more forward, closer to the pivot point, better low speed handling is a result. In addition larger wheels give a significant prop walk effect (I would not install a stern thruster) and shafts gives better longitudal wight balance (if not v drive).
My take on this is that if you use the boat for cruising mostly up to 25 knots and it is a relatively heavy deep v build, shafts are the way to go.
Sorry for the long post, hope it helps in the evaluation.
Momac
Well-Known Member
Shafts are a more expensive option when new, I believe, since setting everything up takes more skill and time. What could be better than mid engine rather than all that weight a the stern?
Annual service is a good investment with legs it seems.
By the way my boat is a single , with leg/duoprop . It used to wander about at slow speed.
Now it is hardly noticeable - most of the time.
Annual service is a good investment with legs it seems.
By the way my boat is a single , with leg/duoprop . It used to wander about at slow speed.
Now it is hardly noticeable - most of the time.