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Sizing an outboard


Mohsen

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Good afternoon hive mind,

 

I want to size a petrol outboard for a little 2x1m metal tender. I’ve never done this before so want to make sure it’s not under powered (like the current electric one is) nor so muscular I’ll look like James Bond in the Lea.

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Ignore the nest, those squatters have moved on. 

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Don't underestimate the weight of lifting and carrying the thing (including fuel). If you want to leave it on all the time, and want something that will push it against the flow on a river, or tidal waters a 4hp may be better. Something like the old Johnson seahorse can be picked up fairly cheap on ebay, and are relatively light. 

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I've got a 5hp Suzuki 4 stroke on a GRP dinghy of about the same size. I used to have a 4hp 2 stroke on one of those aluminium punts on the Thames and it was fine. With the outboard and yourself at the back you might need some ballast on a rubber mat on the floor behind the bow bench - unless you've got someone else sitting on the middle bench.

 

You'll also need something to prevent it getting nicked unless you're removing it from the boat every time. Like generators, outboards have good resale values and get stolen by scrotes.

Edited by blackrose
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3 hours ago, Tony Brooks said:

I would have thought 5 HP would be plenty, that equates to about 3.73 KW to give you some kind or comparison. I expect a smaller one would do, but not sure they are even made.

 

Just make sure you get a short-shaft.

 

I use a 2hp 4-stroke Honda on my boat tender and it pushes against the tides with no problem.

 

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10-8-29e.jpg

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1 minute ago, Alan de Enfield said:

 

Just make sure you get a short-shaft.

 

I use a 2hp 4-stroke Honda on my boat tender and it pushes against the tides with no problem.

 

20191221-113227.jpg

 

20200727-151416.jpg

 

10-8-29e.jpg

That's the same outboard I have, and it copes admirably in tidal waters.Used on a 9ft inflatable avon (the boat, not the river).

Edited by rusty69
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2 minutes ago, rusty69 said:

That's the same outboard I have, and it copes admirably in tidal waters.Used on a 9ft inflatable avon (the boat, not the river).

 

Our Avon is 3.2 metres (10' 5") and copes with two aults and the dog on trips ashore.

Tides in the Menai can run at above 5 knots and we have coped with them.

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1 hour ago, Alan de Enfield said:

 

20191221-113227.jpg

 

5 hours ago, blackrose said:

You'll also need something to prevent it getting nicked unless you're removing it from the boat every time.

Keeping the boat in the dining room seems to be one option...

Edited by David Mack
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10 hours ago, rusty69 said:

Assuming non tidal waters a, 2hp will push that along. Get a two stroke if you want something light to carry that doesn't drop the back end too far. 

 

^^^^This

Many years I had a 3 meter fibreglass dinghy, so larger and probably considerably heaver than your boat @Mohsen I had a 2hp Johnson two stroke which was very simple and reliable, and powered the boat perfectly adequately on a river. It was also light enough to take off and sling over the shoulder….I used to walk quite a distance carrying it like that! So that’s what I’d recommend.

 

Edited by booke23
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10 minutes ago, Mike Hurley said:

I also had a Honda 2HP four stroke on an inflatable that i used on the Avon and K and A and in the sea, worked well, even after i dropped it off the pontoon in Saltford marina.

They are remarkably resilient. Ours took a dunk in salt water once when the dinghy flipped in a strong wind just after disembarking. 

 

I was able to get it out pretty quick, drained the oil and fuel and it started first pull after refuelling and new oil. I think it actually ran better afterwards. 

 

A similar thing happened to the guy on the boat behind. His engine dropped off the back of the tender after it flipped, and was on the sea bed submerged for a, couple of hours. That ran again too without much effort. 

 

Both small 4 stroke hondas. 

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4 minutes ago, rusty69 said:

They are remarkably resilient. Ours took a dunk in salt water once when the dinghy flipped in a strong wind just after disembarking. 

 

I was able to get it out pretty quick, drained the oil and fuel and it started first pull after refuelling and new oil. I think it actually ran better afterwards. 

 

A similar thing happened to the guy on the boat behind. His engine dropped off the back of the tender after it flipped, and was on the sea bed submerged for a, couple of hours. That ran again too without much effort. 

 

Both small 4 stroke hondas. 

 

 

I dropped mine (salt water) after taking it off the tender and trying to climb the ladder off the bathing platform back onto the deck.

 

It took a couple of hours of throwing a grappling hook (yes - it was attached to a line of which the bitter end remained on board) before it was recovered.

Washed it down, drained fuel and oil and replaced - it still wouldn't start after about 10 million 'pulls'.

 

Removed the carb and (long story short) found that there was a 'bubble' of water stuck in the jet and the petrol could not remove it. Blew it out, reassembled and it started first pull.

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9 minutes ago, Alan de Enfield said:

Removed the carb and (long story short) found that there was a 'bubble' of water stuck in the jet and the petrol could not remove it. Blew it out, reassembled and it started first pull

Those small carbs can be a right pita. If you leave fuel in them for any length of time, the jet gets blocked. 

 

Probably the same with most carbs come to think of it. 

 

If you watch the flower of gloster thing on you tube, the young girl in the dinghy loses her outboarde (e4 I think). The young man fetches it for her. Thankfully for him it must have been fairly shallow. I wouldn't fancy swimming with a outboard. 

 

 

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17 minutes ago, rusty69 said:

Those small carbs can be a right pita. If you leave fuel in them for any length of time, the jet gets blocked. 

 

I've always turned off the fuel and let the engine run 'dry', then, close the air vent.

It was particularly important in the days of 2T fuel as the petrol would evaporate leaving the oil to solidify in the carb - not an easy job to clean it out.

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Just now, Alan de Enfield said:

 

I've always turned off the fuel and let the engine run 'dry', then, close the air vent.

It was particularly important in the days of 2T fuel as the petrol would evaporate leaving the oil to solidify in the carb - not an easy job to clean it out.

Thats what I do too, and always drain the carb bowl at the end of the season.

Just now, rusty69 said:

Thats what I do too, and always drain the carb bowl at the end of the season.

There is always the other option, of course. Oars:

 

Simple is good - complex is bad !

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I use an old 5hp two stroke on a 19' GRP cruiser on the canal. Pushes it along at a fair chat and it weighs just over half a ton. Not the lightest engine though for lifting on and off repeatedly. Suspect it would be a bit excessive for a little punt type boat. Also have a Mariner 3.3hp which can move the cruiser no problem. At about 13kg it's a lot lighter but with no reverse gear it's spin round to go in reverse. Something like that, or the 2.5hp version would I think be plenty for a little aluminium tender

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I've had three of those little Honda 2 outboards (same model as in the dining room picture). 

 

Great outboards. One given away as not needed at the time, second one stolen and still have the third one. 

 

However on the dink I now have an Aquamot electric 1.6kw outboard which does the same job as the 2hp outboard but less range being battery powered. 

 

Another great outboard is the Yamaha Malta. Some say these are the best small outboard. 3hp 2 smoke very nicely made and very high quality. Not heavy. 

 

 

Edited by magnetman
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1 minute ago, magnetman said:

I've had three of those little Honda 2 outboards (same model as in the dining room picture). 

 

Great outboards. 

 

However on the dink I now have an Aquamot electric 1.6kw outboard which does the same job as the 2hp outboard but less range being battery powered. 

 

Another great outboard is the Yamaha Malta. Some say these are the best small outboard. 3hp 2 smoke very nicely made and very high quality. Not heavy. 

 

 

Seen quite a few of those over the years. Really seem to last and the owners I've talked to spoke very highly of them. Always found Yamaha engines to be decent quality

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1 minute ago, BilgePump said:

Seen quite a few of those over the years. Really seem to last and the owners I've talked to spoke very highly of them. Always found Yamaha engines to be decent quality

 

The worst outboards were / are Suzuki.

 

I was looking for a new outboard and went to a Suzuki dealer and he actually told me not to buy a Suzuki as it was far too complex and would regularly breakdown.

 

My No2 Son has a Suzuki 8hp for his little 14 foot cuddy fishing boat and it has been nothing but trouble. He had to send it away for a service to Suzuki as no dealers would work on it - it came back from the service and has never run since.

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7 minutes ago, BilgePump said:

Seen quite a few of those over the years. Really seem to last and the owners I've talked to spoke very highly of them. Always found Yamaha engines to be decent quality

Yamaha arrr good. 

 

Interesting outboard was the Yamaha F4 four stroke unit which they produced for a few yars before the 4,  and 6 were the same base model..

 

This outboard was quite light at about 18kg rather than the 25kg of the new F4. It also had a built in tank as well as the option of a remote tank. A very nice little outboard that one. Not many about as after a short time as with other makers the 4, 5 and 6 were produced as the same actual unit which makes the 4 very heavy for what it is. 

 

I've not had one but would be very tempted by one of them. 

 

 

It is this one. The carrying ring is on the front not the back. 

 

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Nice outboard I believe. 

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14 minutes ago, Alan de Enfield said:

 

The worst outboards were / are Suzuki.

 

I was looking for a new outboard and went to a Suzuki dealer and he actually told me not to buy a Suzuki as it was far too complex and would regularly breakdown.

 

My No2 Son has a Suzuki 8hp for his little 14 foot cuddy fishing boat and it has been nothing but trouble. He had to send it away for a service to Suzuki as no dealers would work on it - it came back from the service and has never run since.

My own experiences would echo that sentiment. Had a little old two stroke one which was totally unreliable. Also bought a little cruiser with a beautiful looking four-stroke Suzuki 9.9hp on the back. Engine was immaculate inside and out except it just wouldn't work (knew that when bought it). Never got it to fire up, despite engineer looking at it, and in the end bit the bullet and sold it for parts.

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Hondas are the way to go if the funds are in place. That little BF2 in the living room is about 12.5kg which is good for a 4 stroke. Also has a water cooled leg,/exhaust which makes it quieter than the newer full air cooled types. Plus there is no silly lawnmower clutch to go wrong. 

 

A far better outboard than the newer type. 

 

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