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I looking into replacing an outboard for a Tiki 21. I've used a 4HP Yamaha 2-stroke and feel it a bit under powered against wind and tide. When it's working hard it's noisy and drinks up the fuel.

I wondering if a 6HP 4-stroke would be a better choice. Any advice or experience would be appreciated.

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Most of the 6 HP outboard  are just power reduced 8 HP. Weight and dimensions are equal.  

At the moment I m also looking out for a Motor. I will go on 5 Hp cause of weight and the 5er is really smaller, but I m also unsure If it will be powerful enough going against tide and wind. 

I saw a mono going against river Rhine ( 3 knots stream ) with 5 Hp, looked like possible.

I m also curios what the other say and how many knots they make with their motors ? 

Joerg

Mate, i have spent a bloody frustrating day lifting/taking out a 6hp tohatsu sail drive motor for my tiki 26.The thing is heavy, real heavy, surely on a 21 a lighter motor would be better?

cheers paul.

I have a Honda 5hp on my Tiki 21. It has more than enough power and will push the boat at more than 6 knots in calm water. In my opinion, it is not the power so much as stopping the propeller from ventilating - in a chop the prop ventilates and I can't use more than half throttle. I changed to a smaller pitch prop which helped a lot, but still need to set the prop lower (than the design measurement).

Roger 

I run a 5hp 4 stroke Mariner long leg on ours. Weight to power ratio seems really suitable for her and it pushes her along at 5 knots in the calm just above idle quite easily. I live on a lake so cannot say against a current but wold imagine it to be a well suited motor.

Useful comments ... I note that nice new Suzuki DF4, 5 and new 6 HP engines weight 25kg. I think that is lighter than the 4HP I have been using. But, if I look for a second hand engine (i.e. one that doesn't cost more than the boat!) it will be older and have a smaller power to weight.

I'm wondering also if with a more powerful engine, it might not be flat out against the tide and therefore a bit more relaxing and use less fuel.

5- 6 knots gives not really  spare for security in wind and tide. I lower my mounting about 20 cm. 

Weight and dimensions depends to manufacturer, for example mercury has 6 hp and the power reduced version is 5hp by same weight and size. The best solution is a ultra long shaft length, normally hard to get used on market

I can't overemphasize the ventilation issue - once there is a chop I can't use all of my 5hp, so more power doesn't help. The key thing is to get a longer shaft (25"), or set the motor several inches lower than to plan.

Having read these helpful comments and read other sailing forums comments I think I would currently choose:

  1. 4-stroke: Less noise and better fuel consumption (i.e more range, less weight of fuel on board) Also no messing with pricey marine 2T oil
  2. 5HP: Just that bit extra for English Channel tides
  3. Long shaft: as long as possible but clear of the ground when drying (length ?)
  4. Appropriate prop diameter / pitch for sail boat (not clear on the best spec.? but the standard might not be the best)
I have a 6 hp slonf shaft for my 26. Neither has been in the water. Not very helpful, am I?

These boats really need the 25" shaft. 

I think we should remember that these are AUXILIARY power. These are SAILboats and should be sailed, outboards are only meant as a bit of extra help (as an alternative to warping/rowing?).

About the issue of ventilation, would it help to place the outboard forward, near the center of the boat?

Interesting stuff .. thanks. Here's some metrics from various manufacturers' websites. I can't find much data on older 2-strokes (or 4s for that matter). From this, it looks like you're stuck with around 25kg and can get 6HP for that weight.

Generally shafts are limited to 20''. So is a mod to the transom a good plan to get lower in the water?

Mercury (new)
Power (HP) 3.5 4 6
Long Shaft Length (inches) 20 20 20
Weight (KG) 18 26 26
Yamaha (new)
Power (HP) 2.5 4 6
Long Shaft Length (inches) 15 20 20
Weight (KG) 17 27 27
Honda (new)
Power (HP) 2.3 5 8
Long Shaft Length (inches) 20 20 20
Weight (KG) 14 28 43
Tohatsu (new)
Power (HP) 3.5 4 5
Long Shaft Length (inches) 20 20 20
Weight (KG) 18.4 26 25
Mariner (new)
Power (HP) 2.5 4 6
Long Shaft Length (inches) 20 20 20
Weight (KG) 17 25 25
Suzuki (new)
Power (HP) 4 5 6
Long Shaft Length (inches) 20 20 20
Weight (KG) 26 26 26
Evinrude (new)
Power (HP) 4 6
Long Shaft Length (inches) 20 20 & 25
Weight (KG) 26 26

Here's a link to the spreadsheet. Feel free to add information: https://docs.google.com/spreadsheet/ccc?key=0AiYW8mnScb0udDlKNHZrZk...

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