Power requirement, etc. for 22' trailer-sailer

I'm getting conflicting advice on an outboard for a 1970 Van De Stadt designed Mark 1 Pandora trailer sailer - LOA 21'10"/6.65m, LWL 18'9"/5.72m, Beam 6'11"/2.11m, Displacement 2427lb/1100kg, Ballast 980lb/444kg.

Intention: usual pottering, but sole auxillary for sailing in coastal waters.

Option 1: 2.3hp-4hp 2 or 4 stroke - Lightweight. Cheap. May just about be powerful enough.

Option 2: 5-8hp 4-stroke with battery charging - Perhaps the obvious option.

Option 3: 15hp Johnson 2-stroke - 1 on offer locally... cheaper and lighter than 8hp 4 stroke.

Option 4: two x 2.3-2.5hp units - offering security of two independent power supplies.

I've asked around and have been encouraged towards each one of the first three options (option 4 just struck me a moment ago).

Option 1 would be cheapest and lightest and if it would do the job it would be my preferred option... but several people have been saying I need at least 9-10hp... and I'd perhaps have to investigate solar panels for battery charging.

Note: may have the option of an ultra lightweight 3.5 hp 2-stroke Tohatsu whilst stocks last.

Option 2 seems the safer route... but it's too expensive to leave on the transom(where it wouldn't be insured)... might not be that easy to handle at 55lb/25kg... and I understand that I have to stow it vertically on a mount in the cabin unless I drained the sump first.

Option 3 seems overkill and would cost as much as an 8hp fourstroke, but might not weigh that much more (74lb/34kg) and could presumably be laid horizontally on the cabin floor when at the mooring.

Option 4 could cost the same as option 2.. but how would two 3.5hp units perform compared to one 6hp unit? Not sure. I'd also still be missing the charging circuit...

Any thoughts on the size requirements / anything else would be much appreciated.

 

What you have is a moderately fat little trailer sailor, but it's not a tub. It was typical of the era. A few HP will be more then enough to push this boat anywhere you want. Anything over this is just a waste of fuel as the prop beats the water into foam trying to work.

5 HP would be the maximum you'll ever need. Twins are silly and an electric trolling motor would get you around crowded anchorages or up channels in a pinch. I use a 50 pound trolling motor on my 19' LWL, 2,200 pound sailor. It will lose it's "legs" trying to bring you home in a calm if more then an hour away, but other wise is a light weight, easily stowable option that doesn't stink or make noise,

 

You have noted some points to consider. Others that I think worthwhile:
1. You want a separate fuel tank. A small outboard with its own tank will spill fuel when stowed. Should get in the habit of running fuel out before stowing motor.
2. I do not know your hull but if the outboard is hard to reach for easy pull start and controlling then electric start and remote controls are nice. I expect your transom is set up for an outboard and the controls should all be accessible,
3. 4HP will be enough in good weather. To make way in heavy weather you want a motor with enough power and speed potential to get the hull to squat in normal running. This will be around 8HP.
4. You can get large diameter props on low speed outboards that will give higher thrust and are better matched to your load condition. The motor needs to have enough torque to swing the prop in heavy weather.
5. I expect the 4 stroke will give better fuel economy and maybe wider torque range. Setting up a nice bracket to correctly store the motor when moored would be good for any unit.
6. I agree weight is an issue for handling. Handling more than 20kg in an awkward situation is not easy unless you are used to handling such weights.
7. A long shaft reduces risk of the prop aerating when in a seaway. You can get yacht outboard with 25" shafts. Needs to be long enough to suit the mount.
8. The charging current on the small outboards needs to be checked. It is not much on some. I would go for a solar panel anyhow if the boat is moored because you may need to have a bilge pump powered.

Maybe someone with recent experience and ideal choice will chime in.

Rick W

 

That's encouraging as I could save a fortune with a Tohatsu 3.5hp 2 stroke unit at 13kg: £450 plus just £20 on the insurance sounds appealing though they are now exceedingly rare! I guess it would double up as a tender outboard as well...

The four stroke version costs more and weighs more without, as I understand it, offering more.

Sounds like you'd perhaps point me towards the Tohatsu 6hp Saildrive (123 cc / 7.5 cu.in. with 12V charging, hi-thrust prop, seperate 12 litre fuel tank and fuel-line) would cost around £1,000 and weigh 27kg - probably my preferred option right now.

Edit: Honda equivalent (perhaps without the high thrust) would presumably be the Honda BF5 5 H.P Outboard Standard Shaft - Battery Charging. Weight: 27Kg; Displacment: 127cc - Comes with a 6 year warranty (leisure use only). 12 Litre remote fuel tank.; 3 amp charge coil - with 6 Year Warranty.

The next step up in the Tohatsu range is the 209 cc / 12.8 cu.in. 8hp unit which would cost half as much again and would weigh 37kg (80+lbs): that would meet you spec nicely... but would cost almost as much as the boat did and would seriously increase the insurance costs!

Edit: the 8hp Tohatsu costs as much as the monster that follows... which is the same weight, has twice the HP and would presumably do as much on tickover (quietly for a 2 stroke) as the smaller 4-stroke would at (noisy) full throttle!

NEW & UNUSED Mariner 15HP 2-stroke long shaft outboard engine. Last of the 2-strokes!
Only 35KG in weight, 262cc 2-cylinder, manual start, F-N-R Gears (gear shift on tiller handle), complete with 12.5 Litre fuel tank & line, 2 Year manufacturers warranty.

 

Query: how much performance difference would I find between:

1. 5hp (Honda) or 6hp (Tohatsu) single cylinder 123-127cc 4 stroke (25kg)

2. 6hp twin cylinder 197cc 4 stroke (35kg)

For the sake of 10kg on an 1100kg boat... would I get a significantly smoother engine? Less noise? More torque? Ability to drive a higher thrust propeller and run with fewer revs?

ps. Same dealer is offering an "as new" 2 year old honda BF6 twin (with manufacturer's warrantee) for less than I can get the honda 5hp single cylinder unit new!

 

The Honda BF6 is probably tough to go past. It ticks a lot of the boxes you have. Is it long shaft?

Power - should be enough unless you get in heavy blow. Will certainly push you up to hull speed in still air.

Torque - better across the range so can swing a bigger prop if fitted.

Fuel consumption - should be the most efficient of any outboard in this size.

4-stroke - no fuel to mix (don't underestimate the nuisance mixing can be) but then some care in storing

Weight - reportedly the lightest 6HP on the market - what weight?

Tank - external

Electric - supposed to be 5A charge capacity - how does this compare with the others?

Price - competitive but used - unless used in commercial operation and/or stored badly it should be in good condition. You will not use it much if it is purely a sailing auxiliary.

Comfort - smoother with 2 cylinders and less smell without burning oil. Should also start easier with twin cylinders.

By the way I have used a 4HP on a 24ft trailer sailor and it was OK for getting in and out of tight spots or getting home after wind had left. Would not be adequate for use in any decent wind and sea. So 4HP will work but I would consider 6HP as the minimum if it has to cope with some weather.

Rick W

 

Well... we've taken the plunge: at £775 the "as new" Honda BF6 (2007 model) ticked too many boxes:

* Near enough immaculate, and with 2-3 years of warrantee remaining

* Only 10Kg heavier than a 5hp, single cylinder, 127cc version

* With limited bent back (by previous owner) it's an 8hp unit

* Twin cylinder, 197cc block should be smoother/quieter, generate more torgue and drive higher-thrust prop

* Drives a 5amp charging circuit compared with 3amp on the 5hp version

Will collect next week and feedback once tested!

 

Hope it is a winner.

Looking forward to test report with photos and data -will be useful for others having a similar dilemma.

Rick W

 

I changed an 8hp. Honda for a 6hp Tohatsu(4 stroke) on a 30' yacht.
Tohatsu was a lot lighter and more compact, better charging system and better economy. Performance difference was barely noticeable.
Peter

 

Check the specs on the engine. All outboards (or any engine for that matter) have "base models" upon which they tweak to get more power. The tweaks are typically just different size jets and/or some timing adjustments.

For example a 20 HP Johnson is the base for the 20, 25 and 30 HP models. Upping the jet sizes to the next size and cranking in a couple degrees of advance will make it a 25 HP. Changing up three jet sizes and adding a little more advance will make it a 30 HP. Honda is no different, so check which you have.

In other words, does the head from the 6 HP fit on the 10? Or is it an up sized 5? I happen to know that the 8 HP Honda is the same as the 9.9 HP engine.

The quick way is to check the bore and stroke of the engines just above and below the HP rating you have. For example the 8 HP Honda is a 222 cc engine with a 58x42 mm bore and stroke. The 9.9 is exactly the same, meaning it's the same engine.

 

The new Honda 8hp might be 222cc... but as I understand it, my 197cc 6hp unit (manufactured 2007) was the earlier 8hp unit.

The dealer has pointed out a small bracket that served as a stop on the throttle to limit the maximum revs so that the unit was nominally 6hp. This stop has already been bent down and out of the way: I'm assuming that means I now have an 8hp unit.

ps. For a comparison chart see p16 of http://www.hondaireland.ie/images/ContentBuilder/Marine_Brochure_2006.pdf