Auxiliary Power with Outboard

[peterincalgary]

We have an Allied Seawind 30, modified full keel about the same displacement, when our engine seized up, suspected ring failure the local mechanic suggested a 9.9 L/S, I upped it to 15 HP, I had to make a bracket to get it in the water mostly out of 1" sq aluminium, heavy on gas, and in tight quarters can be a bugger, otherwise it works.

Pitty

[thomm225]

My 5 hp 4 stroke outboard works fine on my 6600 lb Bristol 27. It has the extra long 25” shaft and is on a 4 position adjustable bracket.

It’s in the water as low as the diesel’s prop was on the deepest setting.

I can use it in waves up to 2.5 feet or so.

It’s much better for docking than the diesel ever was. Reverse works fine also plus the motor will turn through about 200 degrees which means it is excellent for docking

[alansmith]

Letta, I will tell you some things I know. When you add a four stroke engine to the stern of a sailboat you will need to get the engineering correct. For example.. is your stern plumb ( straight up down)? Is it sloped( which way)? If you use a pivoting outboard bracket, such as a Garelick or scorpion, you will need to have someone fully understand the travel distance of the bracket that you propose to buy. Then you need to understand the length of the outboard engine’s leg. Why is that important? Because the cavitation plate above the propeller has to be X amount of inches below the waterline. Another thing that has to be addressed is the safety involved of not falling overboard when deploying and retrieving the outboard. The job takes a little strength and can be technique dependent. I’m not a sexist when I say a man has some advantages over a woman in upper body strength. Yes, there are women who are stronger than some men. Please don’t be offended.

The other thing is that most outboard bracket manufacturers require the transom to be beefed up. This not only means thicker but stress is also addressed. My trimaran requires a 2” thickness for my 9.9 hp Suzuki. She weighs in at close to 115 lbs. My skin was only about an inch thick where the mount was. I thickened mine with 1/2 G10 on the inside and outside of the fiberglass to satisfy the Garelick manufacturer’s requirement.

What I recommend for you Letta is use your dingy and outboard as your safety. Keep your primary plant in good shape. Have towing insurance. Trying to beef up your transom would be pretty expensive. You will add a lot of expense and complications. A diesel is a better engine than an outboard. Outboards have their own pluses like cost and serviceability. Trimarans that are light and fast … rarely see a diesel on them.

Wish you luck.

[Adelie]

If you want if for maneuvering in harbor, a 6hp SailPro(high thrust) will do fine. Get the extra long shaft. A lowering bracket and shaft length should be fine.

The Southern cross is about 2,000lb less and but also 2’ shorter. I would expect you could make 6kt with the 6hp.

If you want to be able to hit hull speed against a little wind or seastate I’d get a 9.9hp high thrust.

Any bigger than that’s not worth the money. Prop will start coming out of the water and you will need to be sailing anyway.

Make sure to use backing plates in the stern when you mount the bracket.

[zstine]

Originally Posted by chasfgr

Probably because most don't realise that the gearing is much lower.
The troubles with a transom mounted outboard are manifold, only to be used by the experienced in relatively calm conditions.
My first boat had a 15hp Johnson, on the back - I found that a 2 hp did nearly the same job with far less hassle.
Anticipation is the name of the game.

Outboards don't reverse well because they exhaust through the hub of the propeller. When in reverse they suck the exhaust gas through the prop.

Any 9.9hp extra long shaft will do fine for on a 30ft. Yes, it has limitations specific to large seas, but many get by just fine with them.

The OP needs to decide if he wants a remote throttle and shift. Having those makes driving into a slip where he may need to shift and use throttle a lot easier, however it makes the install more permanent, more difficult.

[Calif.Ted]

Actually an auxiliary auxiliary engine, like wearing a belt and TWO pairs of suspenders. While I understand your concerns it seems extreme to add another outboard to the mix.
I once strapped a 2HP dinghy engine to the swim ladder to get me 1/2 mile in the middle of the night in a pouring rain.

[thomm225]

Originally Posted by zstine

Outboards don't reverse well because they exhaust through the hub of the propeller. When in reverse they suck the exhaust gas through the prop.

Any 9.9hp extra long shaft will do fine for on a 30ft. Yes, it has limitations specific to large seas, but many get by just fine with them.

The OP needs to decide if he wants a remote throttle and shift. Having those makes driving into a slip where he may need to shift and use throttle a lot easier, however it makes the install more permanent, more difficult.

These opinions are always so out there on outboards. Almost as bad as the new gen anchor guys that don't know how to use anything else.

Mine moves the boat fine in reverse, and I come out of my slip every time using reverse.

I do not have remote controls because I refuse to have all that crap on my boat so I use the outboard by hand no external controls just my hands

My 5 hp outboard also works pretty well in waves if you have to get back straight into the wind and have a time limit......

https://www.youtube.com/watch?v=ri0c5GnZ1I8

And on flat water.....

https://www.youtube.com/watch?v=uNl2tPRC-Tw

[Movinon1]

I have a 2 cycle 15hp mounted on a kicker swing down bracket. My stern has a swing down transom/swimstep that allows me access to motor. The kicker bracket is just to keep outboard out of the water. Without the swim ladder, I could not get at the outboard to start it. While under way, I fold the handle up perpendicular and adjust speed, shift gears, and turn off in this position. I'm using a 2 cycle because of weight difference. My 36" Islander weighs about 18,000, and the 15hp will push her along at about 4-5 knots. Have used it on several occasions when the Perkins was being ornery, and darkness was approaching.
Haven't had to, but it could be used as a stern thruster, with the Perkins. I also mounted a small pivoting hoist that I leave connected to the outboard to partially relieve the weight off of the bracket, and to help in mounting it on the dingy. Keeping a can full of gas on board is a pain, but manageable.

[NorthCoastJoe]

My backup is a Guide paddle, in low wind conditions I get one knot paddling at the bow and two knots for short burst. Otherwise sail it. I have done that going into my slip at a marina. I and to paddle about 200 meters.

[Jammer]

Originally Posted by FabioC

Has anybody implemented (or at least studied) something like this on a larger boat (say a high-freeboard 35')?

Probably not at 35'. In the 1960s/1970s there was a period of experimentation with outboards in wells, in some cases on somewhat larger vessels than the 25'-27' maximum size for outboard-equipped sailboats today.

In principle, this could be an extra peace of mind... on many boats, we store the dinghy's outboard on the stern rail anyway, so if somehow some sort of bracket could be devised to be able to lower the outboard to the water... the intended use would be only in case of an emergency (say, losing main engine power just windward of a rock, or something like that), and just to get you to safety to give time until you can raise sails, or drop anchor, or whatever...
[....]

Outboards are an inexpensive, reliable way to get basic propulsion in and out of a harbor and in light airs and calms. They don't do well in heavy seas because the air intake isn't protected from a following wave and because the prop typically goes airborne especially on the unfavorable tack.


Sails and the inboard (if equipped) should be seen as backing each other up.

[Boatguy30]

I would invest this time and energy into making sure the existing inboard is functioning 100%. Maybe check the fuel tank for sludge, check exhaust elbow for carbon, etc.

[boatman61]

Fitted a Suzuki 8.8LS 2X on a Wauquez 37 that I had to take from Seville, Spain to Figuera da Foz, Portugal.
The main engine was dead and needed a rebuild but the new owner wanted her back in Portugal to do a full refit ASAP.
You can see the O/B bracket on the stern as she's launched..
We motored at around 5kts down the Guadalquiver to the sea where we raised sail.. then from just between Lisbon and Peniche we had to start the engine as the wind died, it pushed us along at around 4.5 kts the remaining 100+nm, should add that was not full throttle varied between 2/3rds and 3/4 every so often.
It works...

[Don C L]

Hi Letta, On my 29' old school boat, the outboard is the only auxiliary I got, and it works fine. But, I will say, my boat has no provision for an inboard. If you have a working inboard, stay with that and don't bother with a back-up. Make sure the engine you have is in top shape and go with that. If you MUST add an out board I believe the best option for you is a 9.9 with the power prop or "high thrust" option. The "power prop" is built to maximize its effect in reverse and allow the exhaust to pass both directions. In my boat (that weighs around 8500#) I can motor at about half throttle, go nearly 6 knots and get about 8 mpg which ain't too bad. I carry 15 gallons and I use the engine quite a bit where I am. I happen to have a Tohatsu 9.8, but Yamaha and Hondas are probably the preferred brands. I am happy with mine. You need to have a mount that will allow the engine (most likely the 20" longshaft) to fully submerge and stay that way even in swells, and yet be able to bring the engine up all the way out of the water. I was lucky, the previous owner of my boat was an engineer who fashioned a pretty nice mount/hoist that does the trick. You are welcome to see it in my albums. As far as being around million dollar boats, NO engine will stop you on a dime, but my engine with the special prop puts a lot of thrust in reverse and will certainly slow you down pretty quick. BTW are you sure your O'day 30 REALLY weighs 12,000#? Sounds a bit high to me for that boat. Good luck.

[valhalla360]

An outboard can be a good option...if the boat is designed to accommodate one.

Modern 4 strokes are reliable, powerful and fuel efficient. Especially if you can get a fuel injected model (the smallest still use a carb).

The problem is mounting the engine where it can keep the prop in the water without waves swamping the power head. On a bigger high freeboard boat, that gets more complicated if it wasn't originally designs for an outboard. This is where the extra long 25" shafts come in and help but may or may not be enough.