attaching outboard engine on sailing boat

[wajaja78]

Hi guys,

I would like to fit an outboard engine (10-15 hp max) on my 18/24 quarter tonner sailing boat.

I want to be able to take it off easily if I have to to avoid it getting stolen.

Any advice / website on how to proceed to attach it?

Thanks!

 

[William_H]

Outboard on a sailing boat

I don't know what an 18/24 quarter tonner sailing boat is but assuming it is something like 24ft or less then an outboard will be eminently suitable. However the horsepower could be and should be a lot less if you propose to lift it off for storage.
The motors are usually mounted on a bracket on the transom to one side if you have a transom mounted rudder. The bracket consists of a thick board emulating a dinghy transom on which the motor is clamped. This is mounted on struts about 30cms away from the transom to give room for the front part of the motor.
Ideally the struts will allow the motor to be raised or lowered by about 30 cms. This because often the motor will need to be lower than the top of the transom where it can be difficult to service the motor.
Depending on the shape and weight of the hull the boat may be affected in fore and aft pitch by people on the bow (picking up a mooring) or by a lot of people in the cockpit. So it is desirable to be able to easily adjust the motor height while using it.
The cavitation plate is a plate sitting horizontal above the gearbox. This should be at or slightly below the water level when operating.
You will almost certainly find that you need a long shaft outboard for a sail boat. This has the leg about 12cms or so longer than the standard short shaft motor.(They are quite common) This will allow the motor to be deeper in the water while keeping the engine head out of the water and and as high as possible.
An outboard on a transom bracket does have limitations in that in a big sea the boat will pitch a lot and the motor when trying to drive the boat will become too shallow in the water and lose grip. Resulting in racing engine. This is also called cavitation.
So some boats resort to fitting the o/b motor into a hole cut in the hull forward of the transom. This often puts the o/b right in the middle of the cockpit. To me a real nuisance. To others it is vital. It is difficult to get the motor raised out of the water to reduce drag when sailing.
Other boats have a cut away transom so the motor mounts on the transom itself. One style had a hole cut just forward of the transom with a false transom fitted about 60cms forward of the real transom. The hole is opened out to allow the motor to swing up and aft through the transom.
All of these arrangements mean a lot of modification to the hull to make the o/b well.
So my advice is look at chandlers catalogues for O/B brackets and get one that has spring assistance and a good range of height adjustment and fit it to the transom.
If you do not have a transom ie canoe stern then it gets difficult. A recent thread had photos of options for mounting a bracket.
For my 21fter I have a home made canter levered bracket with 3 height adjustments using a 6HP long shaft. I have used it in rough water and while it is not ideal it is OK. Mostly I sail though. I can with difficulty lift the motor from inside the cabin out onto the bracket. (Tie a rope on to the motor first so you don't lose it if you drop it). good luck olewill

 

[TQA]

A 10 to 15hp four stroke is going to weigh at least a 100 lbs more than most people want to muscle around esp. if you are working from a dinghy.

If you are working from a dinghy then I would look for a 2 stroke saildrive around 6 hp.

Otherwise it is a job for some mechanical assistance. A boom extension and block and tackle might work.

 

[Seajet]

Knowing the Eighythene ( sp ?! ) 24, I'd think a 5hp outboard would do, that's the most powerful one gets before outboards become stupidly heavy, and the boat should be able to sail out of trouble if there's any wind at all.

I suspect the outboard may need to be on a track up & down the transom ?

It might be an idea to try to get hold of a secondhand 2-stroke such as a Mariner or Yamaha 5, they're a lot lighter than the 4-strokes which legislation insists on for new engines.

I have a 2-stroke Mariner 5, and have happily motored across the Channel Poole - Guernsey etc in calms and light winds.

Unless you fit remote controls, it will be a pain having to lean over or through the pushpit to adjust the throttle or change gear, getting into a tight marina and having to face backwards at the critical moment might be rather too interesting, though you might be able to broadcast your approach and sell tickets, followed by an appearance on Youtube !

Is the boat engine-less, or is this a case of an inboard packing up and this being the quick cheap solution ?

It must be said, an outboard on the back will do nothing for the looks of such a racy boat.

 

[Even Chance]

I have a 4hp 2 stroke yamaha on the back of my E Boat, and have happily motored across the Moray Firth at 5kts with it. I made a large cavitation plate out of 1/2" thick plastic for it and it made a HUGE difference to the drive. I can motor into the big tidal flows we have up here easily as well, and have but a few times wished for a wee bit more power to push against the flow around headlands etc.

 

[Even Chance]

Will also say that I dont have remotes, but I pushed a length of 20mm plastic conduit pipe ove the gear selector to make it easier to move/reach. The throttle arm is fixed into a slot in a wooden block on the transom so it cant move sideways and rotate the outboard. Im using an old British Seagull outboard mount. Solid as a rock!!

 

[Tranona]

Hi guys,

I would like to fit an outboard engine (10-15 hp max) on my 18/24 quarter tonner sailing boat.

I want to be able to take it off easily if I have to to avoid it getting stolen.

Any advice / website on how to proceed to attach it?

Thanks!

As already suggested a 5-8hp motor is more than adequate. The attachment will depend on the shape of your transom. You have a choice of two shaft lengths and it is more common to use the longer 21" leg so that you can get the powerhead high enough to operate the controls. The distance to measure is from the top of the mounting board to the static waterline. There are many different types of bracket, which can be fixed, run up and down on sliders or perhaps most common spring loaded types where the mounting board and engine can be lifted vertically out of the water when sailing. Usually it is not worth installing remote controls but a remote tank is useful to give extra range.

 

[Lakesailor]

If it is an Eygthene my comments were of no use.

 

[rob2]

Just for reference, here is a link to a Eygthene website. Origiunally the boat was designed to have an inboard petter mini-6.

http://www.eygthene24.com/boat.php

Rob.

 

[rob2]

Just for reference, here is a link to a Eygthene website. Originally the boat was designed to have an inboard petter mini-6.

http://www.eygthene24.com/boat.php

Rob.

 

[catalac08]

I think what is best for your needs is a 6HP saildrive engine. These have a higher gear ratio than a standard or long shaft engine which is better for pushing a displacement boat. They also have an ultra long shaft ( 25" shaft) which is about 4/5 inches longer than a normal long shaft engine and that will be in the water more of the time than a long shaft.
I know Tohatsu do a saildrive in this size and maybe some of the other manufacturers. I would try and source a good second hand 2 stroke saildrive engine which will be much lighter than a 4 stroke. Good luck with this.

 

[onesea]

Knowing the Eighythene ( sp ?! ) 24, I'd think a 5hp outboard would do, that's the most powerful one gets before outboards become stupidly heavy, and the boat should be able to sail out of trouble if there's any wind at all.

I suspect the outboard may need to be on a track up & down the transom ?

It might be an idea to try to get hold of a secondhand 2-stroke such as a Mariner or Yamaha 5, they're a lot lighter than the 4-strokes which legislation insists on for new engines.

I have a 2-stroke Mariner 5, and have happily motored across the Channel Poole - Guernsey etc in calms and light winds.

Unless you fit remote controls, it will be a pain having to lean over or through the pushpit to adjust the throttle or change gear, getting into a tight marina and having to face backwards at the critical moment might be rather too interesting, though you might be able to broadcast your approach and sell tickets, followed by an appearance on Youtube !

Is the boat engine-less, or is this a case of an inboard packing up and this being the quick cheap solution ?

It must be said, an outboard on the back will do nothing for the looks of such a racy boat.

Unless it has changed recently up to 6hp is single cylinder 6+ to 15hp is twin cylinder and that's where the weight is. I have 6hp (on 24') and would not want to lift any more on and off before sailing.

The remote controls I sore where a pain to connect and disconnect if you are lifting off each time, consider some 2" plastic drain pipe as tiller extension...

Then I did not opt for charging either the current it produces is very minimal.

I agree about the looks thing although if inboard is dead it might simply be not worth replacing? at around 4-6k

Just for reference, here is a link to a Eygthene website. Origiunally the boat was designed to have an inboard petter mini-6.

http://www.eygthene24.com/boat.php

Rob.

As I understand outboards although rated by Hp do not have same push as in boards, slower prop speeds and bigger props on inboards?

 

[Seajet]

Onesea,

that's where 'saildrive' outboards come in, with a prop & gearing designed to suit pushing a cruiser.

Such engines often have better charging systems too, and as my Mariner came with internal & external tanks I removed the internal one; when I lifted a friends' engine, identical but internal tank only ,I was surprised how noticably heavier it was.

Removing the internal tank doesn't just save a tiny bit of weight, it avoids spilling petrol in the locker when the engine is stowed for proper sailing.

I have a charging coil but only bother connecting it if motoring a long way in calms etc, the 30 watt solar panel usually keeps everything topped up and as you say standard charging is feeble, I think 3 amps.

However my 2-stroke Mariner 5 standard outboard ( in a well so no problems with controls etc ) pushes my Anderson 22 along fine; in fact I - and a chum with an identical set-up - had to slightly trim the prop to get full revs; with these engines 5hp is the largest relatively light engine available.

 

[Even Chance]

Seajet, yer a star!!!
Im not getting full revs on my 4hp Yamaha. If I take a wee bit of pitch off the blades by bending them slightly, I can get higher revs. I have a spare/old prop I can try it on that has a bent blade after a stone strike in a loch.
Will have to jig it to get em the same mind, and static balance.

 

[Seajet]

Even Chance,

don't know about bending prop blades, I actually filed a bit off; obviously one has to be careful to keep it even for balance / vibration, and go by trial & error, a little at a time.

 

[Even Chance]

Sounds good like.
By reducing the pitch instead of the swept area, you can increase revs whilst keeping the pulling power. Its a wee bit like a home brewed saildrive prop!
Ive made numerous props for model boats out of brass and stainless, in a jig that I developed. The blades are pressed in another home made jig on a fly press. The largest 'Ive made was for an 8 foot long scale model tug boat that was 4 1/2" diameter. My outboard prop aint that much larger!
Im willing to try it out on my old prop first. I'll post the results in the summer....