DRAGONFLY Trimarans User Forum

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DF920 Motor

These are archived postings from the first Dragonfly User Forum from 2001-2006. Lots of useful information to be found here!

Here you will find all the information about the Dragonfly 920 Motor.

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Controls | Inboard | Propeller | Tiller Linkage | Service | Tips

Remote control f. outboard
[from: Malcolm Ratcliffe, UK, 5 Oct 2005]
Re: My question no 2 from 15 Sep 2005. Have a look at www.powertiller.net
A simple outboard motor remote control to fit on the tiller.

Re: Honda electric tilt for DF920 ?
[from: Larry, USA, 20 Sep 2005]
The engine mount is longer on the Honda and extends lower than the Yamaha, so a Honda would not fit a DF-920 that was made prior to the factory switch to Honda. The problem is that the Hull/deck joint will interfere, so you would need a stand-off bracket to move the Honda aft far enough to clear the seam (about 5+ centimeters). If you can’t find a bracket on the market you could fabricate one with aluminum I-beam stock and marine plywood or teak. The electric tilt would be a nice upgrade, but it also adds weight all the way aft.

Honda electric tilt for DF920 ?
[from: Malcolm Ratcliffe, United Kingdom, 15 Sep 2005]

I currently have a manual start 9.9hp Yamaha 4 stroke on my DF920, extra long shaft, with tiller handle controls. It works fine, and there is nothing wrong with it. However, one day when I can afford it, I fancy changing to maybe the Honda 9.9 hp as fitted to current 920s, with electric start. I have a few questions, though, and wonder if you lot out there might have some answers and comments?

1) Do you need remotes with the Honda, or can you easily reach the tiller handle version controls.

2) If you have remotes, would they fit fore and aft in the cockpit, because all the ones I’ve seen have been fitted to the aft face of the cockpit, i.e. transverse. I had a catamaran with that arrangement some years ago, and did not like it:- in panic situations, you could easily push the lever the wrong way!

3) I notice that on some USA Honda Websites, that the Honda 9.9hp electric start is also available with electric tilt. Has anybody got this, or would know if such a USA spec engine might be obtainable in UK? My present Yamaha is very hard to tilt up, and I doubt that my wife would be strong enough to tilt the engine up out of the water. Thanks, Mal

Re: Honda BF15 or BF20 outboard motor
[from: Tony van Wouw, Canada, 4 Apr 2005]
The BF15 is actually identical to the BF20 except for a restrictor plate between the carburetor and the intake manifold. The full power of the engine can be made available by simply boring out the restrictor plate to the throat size of the carburetor.

Honda BF15 on DF920 Extreme
[from: Colin Innes, United Kingdom, 3 Jun 2004]

I have just taken delivery of a new 920E and I have fitted a Honda 15 which is 4.5 kg heavier than the 9.9 and is much more powerful the mounting bracket was stenghened by Jens Quorning but not a large alteration. The engine works very well and has plenty of power I do not think the 20 is necessary as you do not do a lot of motoring! also it has the great advantage of a power tilt which does make life a lot easier and is very useful if you need to get the engine down and your hands are full!

The boat is great I am just getting used to how it all works which takes a little time.

There appears to be confusion over the Yamaha 9.9 it is still in production but the casing has now expanded to make it too wide to fit

Good sailing

Re: Anti-cavitation plates, do they work?
[from: Darryl Brathwaite, Caribbean, 26 May 2004]
Anti-cavitation plates, do they work?
Steadier, smoother, drive when motoring or motorsailing to windward in choppy seas.

Anti-cavitation plates, do they work?
[from: Bo Wetzel, 18 Feb 2004]

Has anybody tried to use one of the fins (see photo), which are sold for outboard motors, on the DF920 to reduce the cavitation problem (sucking air from above into the propeller) when using the boat in slightly rough sea conditions (waves) ?I used these things ones on a semi-rigid inflatable and found they work for starting to plan earlier and therefore reducing fuel consumption. So maybe it helps with the cavitation problem?

Please click on the photo to see it enlarged

Mounting one of the new Honda 20hp outboards?
[from: Tony van Wouw, Canada, 29 Jan 2003]

Has anyone considered mounting one of the new Honda 20hp outboards? The weight of these units is not much more than the Yamaha. Any idea as to what the speed might be with a 20hp engine?

Based on my preliminary investigations an offset bracket would have to be made since the transom clamp is about 10 cm longer than the Yamaha clamp. Additional bracing to take the higher torque could be provided by extending the bracket to the bottom of the transom.

31 March 2002, Yamaha 9.9FT discontinued!
According to Jens Quorning Yamaha has stopped production of the 4-stroke Yamaha 9.9FT.
All new Dragonfly 920s will be fitted with the HONDA 10BF which has a similar performance.
The benefits of this new motor are: Quieter running, longer shaft, which means the propeller is 7 cm deeper in the water. Apparently it is also easyer to tilt the motor as it is better balanced. Unfortunately the motor cost more than the Yamaha and needs a larger/modified support. Looking forward to hearing from the first person who fits one to an existing 920.


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Inboard Engine for DF920-57
[from: Ernst Fellner, Germany, 26 May 2002]

The DF920-57 hat from new an Yanmar 2GM-Saildrive fitted. Jens has built it in following my suggestions and drawings. Jens preferred an 1 Cyl 9 PS Engine because of weight. But I think the 2 Cyl is the right choice. Extra weight compared to an 9.9.PS Outbord is ca. 80 kg, but the Engine ist closer to the center of gravity, and is much more secure because the propeller will not come out of water in high seas. Max. Speed with Flex-o-Fold 2-Blade Prop is 8,0 kn. The Cockpit Floor is raised about 10 cm in the rear part. A drawing ” als Anlage”. I think this is much better than an outbor engine. I told Jens that a boat which costs about 100 000 Euro should have an inboard engine. The extra weigt is merely one Person in the cockpit. Disandvantage is that you can not fall dry.

The extra cost in October 1999/May 2000 were as follows:

Motor 2GM20 SD: 18.380 DM (9.400 Euros)

Tank, Folding-Prop, Exhaust, extra bettery etc: 4.320 DM (2.209 Euros)

Fitting of Motor: 1.500 DM (767 Euros)

Raising of Cockpit Floor: 2.250 DM (1.150 Euros)

These were the cost at building stage of a new boat, it might be different when converting an existing Dragonfly.

Pictures can be seen on the home page of my son:www.dragonfly.martinfellner.de/

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Propeller on Yamaha 9.9
[from: Larry, USA, 20/10/2001, whippet@nstsystems.net]

The standard propeller (11 3/4 x 9 1/4)on the Yamaha 9.9 is the correct one. I experimented with a steeper pitch (11 3/4 x 11)to see if I could get more top speed, but it overloaded the engine without increasing top speed.

I have a tachometer and could do objective measurements. With the standard prop the boat averages about 6-6.5 knots at 4,000 RPM (I consider that cruising speed), and does 7-7.5 knots at 5,000 RPM. With the higher pitch prop, the engine rans rougher, and could not exceed approximately 4,200 RPM and 7 knots. The slow speed thrust was notably better with the standard prop.

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Easy to make Tiller-Motor Linkage
[from: Bo Wetzel, France/UK, 25/10/2001]
I’ve made a simple (and cheap: approximately €20) tiller-outboard motor linkage which immproves navigation under power at low speed (in harbours for example) dramatically.

Click on the photo to see the details and how to make one (with photos!).

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Check for salt deposits in cooling pipe
[from: Bill Fraser, UK, 10 Aug 2002]
Yamaha 9.9hp: You can throw the pipe cleaner away if you clean the plastic hose connector just inside the motor cover – mine was clogged with salt crystals and now the water flows fine.

Pipe cleaner for cooling water outlet on outboard motors
[from: Bo Wetzel, France, 14 May 2002]
Not long ago I was given a pipe cleaner (yes, a fury length of wire, which is normally used by pipe smokers to clean their pipe!) and a handy tip by Bill Fraser. He told me that a pipe cleaner is very useful for unblocking the water outlet at the top of the leg just below the actual motor which normally gives a healthy spouting of cooling water. The pipe cleaner is ideal for keeping this cooling water outlet free of salt deposits.
It worked for me! Thanks Bill! A handy and easy way to keep your outboard motor’s cooling water flowing.
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Check your Pull-Starter on the Yamaha 9.9
[from: Francis Muret, France, 30/10/2001, fr_muret@club-internet.fr]
Priodically check your pull starter assembly. Make sure locking nut on the vertical axis is secure otherwise the horizontal splint might get lost. If the splint is not there the ring will not come up and the pull starter will not engage.
[Vérifier périodiquement le contre-écrou de l’axe vertical du lanceur. Sinon la goupille horizontale peut s’échapper, la bague ne se lève plus et le lanceur ne s’enclenche plus.]

Secrurity Switch prevents Yamaha from Starting
[from: Francis Muret, France, 30/10/2001, fr_muret@club-internet.fr]
The cut-out is normally in the OFF position. It’s only ON when inserting the security plastic bit. To overcome problems with this cut-off switch simply disconnect the black or the white cable on the motor.
[Le coupe-circuit de sécurité ou le bouton d’arrêt restent OFF. Essayer de démarrer en débranchant alternativement l’un des 2 fils du circuit (noir et blanc sur mon moteur.]
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