Surface drives or outdrives

[mark.saunders]

I have been looking around to get a bigger craft and was wondering what is it that determines if surface drives are needed instead of outdrives? what are the criteria anyone know?

[Toffy]

don't know, but I 'd like to follow this thread

[PerformanceDodge]

Originally Posted by mark.saunders

I have been looking around to get a bigger craft and was wondering what is it that determines if surface drives are needed instead of outdrives? what are the criteria anyone know?

I am no expert, but from practical experience there are a lot of pro’s and cons, based on efficiency, maintenance, cost of repair, application and life span. Depends a lot on what type of boat, whether its left in the water and how deep your pockets are..

Stern drives
Good maneuverability. Relatively efficient as can be trimmed to suite conditions and speed. Corrode if boat left in the water, probably 10 year life span if maintained well i.e. cleaned of once a year anti fouled and new anodes. Duo props have better grip, get on the plane quicker but when props corrode or damaged twice as many props to replace. Props can usually be changed whilst boat is still in the water. Single prop drives easy to change if sports boating and changing to suit conditions or activity. Single drive duo prop prevents stern walking and more stable, better turns at speed.

Shafts
Good maneuverability. Not as efficient as always pointing down at a slight angle and dragging a long shaft thought the water and no trim facility. Generally low maintenance, clean off once a year and new anodes. Run over a sand bank or hit a submerged object easy to damage a prop or shaft and its boat out of the water to repair. More expensive for props as usually bronze.

Surface drives
Poor maneuverability. Very efficient, as low drag and usually can be trimmed. Ideally suited to high speed craft. Low maintenance, very expensive props.

Jet drives
Good maneuverability. Very inefficient, no danger of props in the water. Good for jet skies, shallow water and rescue boats.

My preference would be. Sports or race boat up to 40 feet, stern drive. 40 feet plus sports cruiser shafts. 40 feet plus race boat or fast cruiser surface drives.

But this is only mu humble opinion

[Cookee]

Originally Posted by freddy21

I am no expert, but from practical experience there are a lot of pro’s and cons, based on efficiency, maintenance, cost of repair, application and life span. Depends a lot on what type of boat, whether its left in the water and how deep your pockets are..

Stern drives
Good maneuverability. Relatively efficient as can be trimmed to suite conditions and speed. Corrode if boat left in the water, probably 10 year life span if maintained well i.e. cleaned of once a year anti fouled and new anodes. Duo props have better grip, get on the plane quicker but when props corrode or damaged twice as many props to replace. Props can usually be changed whilst boat is still in the water. Single prop drives easy to change if sports boating and changing to suit conditions or activity. Single drive duo prop prevents stern walking and more stable, better turns at speed.

Outdrives can last much longer than that if anodes ore maintained. Less efficient than surface drives due to mechanical losses from the bevel gears and drag of the gearbox.

Shafts
Good maneuverability. Not as efficient as always pointing down at a slight angle and dragging a long shaft thought the water and no trim facility. Generally low maintenance, clean off once a year and new anodes. Run over a sand bank or hit a submerged object easy to damage a prop or shaft and its boat out of the water to repair. More expensive for props as usually bronze.

Surface drives
Poor maneuverability. Very efficient, as low drag and usually can be trimmed. Ideally suited to high speed craft. Low maintenance, very expensive props.

Nothing wrong with the manoeuvrability of a surface drive boat, I should know I drive one. Arnesons are trimmable although with less effect than outdrives. Props needn't be much more than any other props. Arneson's publically admit that the only reason they don't sell more is that they don't offer a full package in terms of a full engine and drive although they do offer a gearbox and drive package.

Jet drives
Good maneuverability. Very inefficient, no danger of props in the water. Good for jet skies, shallow water and rescue boats.

My preference would be. Sports or race boat up to 40 feet, stern drive. 40 feet plus sports cruiser shafts. 40 feet plus race boat or fast cruiser surface drives.

But this is only mu humble opinion

In my opinion surface drives are good for down to 30' or maybe less although application vary. Obviously you're not going to bother with slower boats and anything under 50 mph isn't going to benefit as much from the surface drive advantages.

[mark.saunders]

if a retro fit was in order how do you decide what to do? is it personal choice!!!

[Cookee]

Originally Posted by mark.saunders

if a retro fit was in order how do you decide what to do? is it personal choice!!!

Ok - what hull and what power? there is a cost implication as well .........

[Toffy]

http://www.arneson-industries.com/pa...ucts&id=drives

[andy21]

http://www.arneson-industries.com/pa...ravoConversion

This looks interesting... Guessing it's mega bucks!

[mark.saunders]

I was looking at either a tomahawk 37 or apache 45, then re engining it to make it go like it looks!!! but I don't understand why some boats end up with surface drives and some with outdrives, it doesn't seem to have anything to do with engine Hp when you reach a certain size or indeed boat length. is it down to boat-hull style!!!! or simply personal preference.....

[Marinautic]

Originally Posted by andy21

http://www.arneson-industries.com/pa...ravoConversion

This looks interesting... Guessing it's mega bucks!

Last time I enquired, a complete drive, with transmission was around $22k

Originally Posted by freddy21

Surface drives
very expensive props.

If you go with the Bravo Conversion, you can use Merc props with an adapter

[Cookee]

Originally Posted by mark.saunders

I was looking at either a tomahawk 37 or apache 45, then re engining it to make it go like it looks!!! but I don't understand why some boats end up with surface drives and some with outdrives, it doesn't seem to have anything to do with engine Hp when you reach a certain size or indeed boat length. is it down to boat-hull style!!!! or simply personal preference.....

Considered putting an engine and drive in a Tomahawk for racing but I don't think they would stand as they were built for small diesels originally, I still fancy one and I'm sure it would be great as a leisure boat upgraded with sensible power. Sunseeker use a different fixed surface drive (Trimax) as standard although they offer Arnesons as well now.

Given the choice and the budget a Tomahawk with Arensons and a pair of Yanmar 370's would be perfect.

[mark.saunders]

I wonder what that would get up to cookee

[Cookee]

Originally Posted by mark.saunders

I wonder what that would get up to cookee

Good question - our raceboat does 70mph with the 260's so it will do that with a bigger heavier stepless hull easily I would think - ASD6's or 7's would do the trick - it would make it a very expensive old boat though! Yanmar BY260's would be more sensible and still go over 50mph I would think?

[Boatless-Again]

I think the comments on surface drives are bit off. Everyone seems to try and say they are difficult to dock and such but the actual operators never complain of this. Reading the comments of operators that have converted claim they are basically the same as an I/O (well that is from the operators that are using Arnesons at least) The boats are not all fast, I googled them and there are many smaller slower boats on youtube for example that are neither large, fast nor expensive. Propeller cost issue, Mercury makes the propellers for the boats that are under 15M so that is a mute issue and there are some very expensive bravo propellers out there also. I guess my point is that there are good and bad but the bad rumors are worst than the bad facts.

[Athito]

I spoke to Arneson a while back when I was thinking of re-engining my Sunseeker Superhawk 37 (same hull as Tomahawk).

I was really interested in the Bravo conversion kit...they would not recommend it for continuous salt water use due to corrosion issues and suggested I go ASD8 instead which is brass not aluminium.

Bravo Conversion Kit #7M $23,125.00 each

Many boats in the US are trailered so salt water corrosion is less of an issue.

With the Yanmar or Cummins 480's they suggest the ASD8 In Line Drive assembly with Twin Disc Gearbox MG5061A with the 1.54:1 reduction ratio for example, is a very common package.

The ASD8 in inline units cost $16,020 each plus accessories.
http://www.arneson-industries.com/pa...oducts&id=asd8

ASD8i drive units which incorporate an in line drive unit with a transmission that slides onto the input shaft of the drive. These are made in Bronze so if the boat stays full time in salt water this would be a smarter choice. This will require some transom work and the engine will go forward some 6" I believe though.
http://www.arneson-industries.com/pa...cts&id=asd8i-8


RikWimp@Arneson-Industries.com is the guy to talk to - really helpful.