High thrust outboards

[Jock_S]

I have recently purchased a 19' Hardy Regatta. I propose to use it for coastal trips but also want to
trail it to inland waterways in the UK, France and Holland. I appreciate that a 40 / 50 hp is usual for
this boat. I've been reading Marian Martin's "European Waterways" and have noted that torque is
what really matters on inland waterways.

The questions are:

Would an 8 or 9.9 hp Yamaha high thrust have sufficient power and could I expect 4 to 6 knots?
Would it be as economical as a 40 / 50 hp standard 4 stroke outboard running at low revs?
Would a 50 hp high thrust outboard lift the boat onto the plane?
As a matter of interest, what effect would I get from a 25 hp high thrust?

I suppose I am really looking for multi purpose if this is possible.

Advice on pros and cons please!!

 

[jfm]

Re: High power outboards

Jock:
Imho there is much nonsense talked about torque. The laws of physics say that power is mainly what matters. You say you plan coastal trips and therefore I would strongly recommend the 50hp option. At times you will need speed (fighting a tide, bad weather approaching, fighting waves etc) and 10hp on that boat will be like having a food mixer dangling over the back. 25hp will be better but still too small imho. Even 50hp will not be blisteringly fast, but it will allow you to make good progress if you find say a 5knot tide running against you. With a 10hp you would be almost standing still. 10hp is fine for canals in that boat, but is not safe at sea imho, and doesn't do the boat justice. Ignore the "high thrust" claims, that's splitting hairs, basically 10hp is 10hp, laws of physics.

4 strokes are nice but it's questionable whether the cost is justified. Modern 2 strokes are excellent. If you want to run a 50hp outboard slowly for several hours on canals etc it will be fine, no harm done at all

Best wishes

 

[BarryH]

As JFM says, theres no substitue for power. The other angle you need to look at is, if you go for the smaller option it'll be running on the limit most of the time. Whereas if you go for the bigger option it won't. So the bigger option will be less stressed an last that bit longer. The smaller option will die sooner and the wear will be quicker.

As the yanks say " theres no substitute for cubic inches"

 

[kimhollamby]

Agree, plus...

...you'll find the difference between fuel burn on 50hp and 10hp on canals not worth worrying about.

However, the four-stroke does have an inherent advantage of being about 20 per cent more fuel efficient than a conventional two-stroke (the direct injection two-strokes that have equitable figures to four-strokes are not available down in the 50hp bracket). So sea range is better. Plus the four-stroke will be virtually inaudible at slow speeds and the exhaust fumes from it will be a bit less smelly on a hot canal day with a breeze into the cockpit if you have anyone onboard who is a bit sensitive to such things.

Look around for deals - the 50hp four-stroke market is hotly contested now.

Some might of course argue for having both; the 50hp as a main and a 10hp as an auxilary but that's a lot of weight, you've got to bolt an outboard bracket on to take the second motor and it cannot be easily used on its own effectively inland because only the main will be connected to throttle and steering gear.

If you do at all opt for a 10hp outboard, don't forget that the standard out of the box prop is unlikely to be much good for your boat; certainly worth checking.

kim_hollamby@ipcmedia.com

 

[Chris771]

Re: Agree, plus...

Many years ago when I had little canal boats 10 hp 4 stroke Honda or Yamaha seemed to be the thing to go for. Pushing Norman 20 and Buckingham 22 my Honda used to run at about half throttle at about 4/5 kts. Regarding propellors, I did experiment with a 1" finer pitch on my Honda 10hp, nett result was improved acceleration, higher revs, more noise, more fuel. So, I went back to the standard prop, it would slightly overtorque at full throttle and not pull max revs, but it was quieter and more economical and still easily exceeded canal speeds. For a 19' boat it should be fine on a canal with standard prop, giving better economy rather than performance. Something I always did was make an aluminium rudder to clamp on to the outboard leg, with the plate about 100mm aft of the prop. It always made steering much more positive and reduced the near continuous need to apply steering corrections that boats without a keel need at displacement speeds

Kim's comments about fuel consumption of 10 & 50 Hp engines at displacement speeds being the same surprised me, but I assume that his statement is backed by a comparative test somewhere.

When I was canalling, I noticed that most people who brought larger outboard engined boats from the sea eventually seemed to end up with a 10 HP. Of course for seagoing a larger engine is needed, horses for courses. I think it will be difficult to satisfy both criteria with a single engine.

Don't really think the wear and tear consideration for smaller engine running harder is particularly valid. I know some little Hondas that have been running for near on 20 years with regular maintenance. I think most people on this forum get fed up and change boats long before that stage is reached.

It never ceases to amaze that some canallers keep the same boat for half a lifetime of creeping along at walking pace...........but then at 4 mph......... performance and seakeeping are really not an issue.

Chris

 

[grays]

Re: High power outboards

If your using a 2 stroke on the inland waterways especialy high HP, you are asking for trouble. 2 strokes are designed to rev high. At low speeds they will not generate a high enough temperature to burn off the lubricating oil from the spark plugs. This will cause poor starting and unreliable tickover very bad news in locks etc. Go for the 50HP but make sure its a 4 stroke if you intend using it in the inland waterways.

<hr width=100% size=1>