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Old 08 December 2010, 04:24   #1
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10HP to 15HP, how much better?

hi all. my first post and end of first years boating.

I have had my zodiac futura (mark 1 ,airdeck, 1999, 11.5ft) for a year with a 10hp tiller yam 4stroke (2008 motor) and had loads of fun in it, but would like a bit more power. the 10hp when on the plane goes quite well, but it is its ability to get on the plane quickly in anything other than ideal conditions that is the problem. you have to coax it. heading back against the swell/waves can mean no planing. five minutes in one direction can be 20 back the other way.

so, to the solution. a 15hp 2stroke? i am looking at a late 2000's (must be as new as possible) merc, mariner or yam, (35kg max) motor. How much will this improve things? do any of you have experience of the same situation. is the 15hp the answer to all my problems. will the boat get onto the plane far more easily and quickly? will it be straight back on the plane after a tight turn? etc.

also, just out of curiosity, the weight of a 15 is about as much as i want to carry, but the boat will take up to 20hp. it seems imposible though, to buy a late (20004/2006) 20hp 2 stroke? they are all old 80's or early 90's. were they not made at this size in the 2000's ?

hope you can help
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Old 08 December 2010, 05:59   #2
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Firstly, Welcome to ribnet!

You pretty much hit the nail on the head there - 50% more power = more grunt to get on the plane. I can't give acual comment on that setup as I've never used one like it, but if it's OK-ish at the moment that should do the trick. (I went form 25 to 30 Hp on the back of an SR4. The time to plane was substantially reduced with a moderate power hike).

As for newish 2-strokes, I guess that is a popular size. Polwart has one, so they were made, but 20 is a bit of a no mans' land. Too big for generic cart-about-able SIBS, and too small for smaller Ribs. Hence I suspect not as many as those around and who have one want to keep it. If you can be patient, one will show up eventually.

Also any reason for 2004/6? To put it in perspective the museum on the back of mine is an early 80s machine according to the paint job. The desgn started life in the 60s..... Put another way a 2006 engine may be the same lump as one built in 1999 with a different paint job.

The thing with outboards is a 3YO one left out and driven with the wrong prop for all that time could be in far worse condition than a 10YO machine that has been looked after.....
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Old 08 December 2010, 07:14   #3
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thanks for the thoughts. a 15 has to be better. i am just wanting it to be loads better if i have to spend another 1000 or so. I hate spending 1000 and being disapointed.

the reason for as new as possible is i have been told so many times, buy as new as you can afford for reliability. i have had a number of modern classic bikes and cars and the breakdowns and tinkering are all part of the fun. not with a boat though. stranded at sea, no thanks. i want my boating to be as modern as possible.

this will now probably spark an old verses new engine debate. go for it, but any more thoughts on the 15hp upgrade would also be gratefully received
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Old 08 December 2010, 07:48   #4
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Country: UK - England
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Make: Honwave 3.8 IE
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Engine: Honda 15hp 4 stroke
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Hi there.
Just wanted to say that after adding the hydrofoils to my 15hp engine I noticed a marked improvement, especially ease of getting on the plane. Only 20, well worth it on my opinion.
Not everyone on here seems to like them but I would give it a try.

Jake
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Old 08 December 2010, 08:47   #5
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How about this, 18hp Tohatsu 2 stroke, weighs 41kg mind - same as their 15hp motor.

For sale but nothing to do with me
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Old 08 December 2010, 09:19   #6
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Quote:
Originally Posted by 9D280 View Post
As for newish 2-strokes, I guess that is a popular size. Polwart has one, so they were made, but 20 is a bit of a no mans' land. Too big for generic cart-about-able SIBS, and too small for smaller Ribs. Hence I suspect not as many as those around and who have one want to keep it. If you can be patient, one will show up eventually.
I do indeed! This was a late model about a year before they stopped importing 2 strokes in Europe. I had no problems sourcing it at the time. There are at least another 2 people with the same engine on here, so they were available but as 9d280 says those who have them will probably be happy with them. One other point is that, certainly for Yamaha, the engine was essentially identical to the 25 HP - so you could get more power for the same weight when buying new.

That 18 HP tohatsu that Willk has linked to is a highly regarded little engine, and just light enough for a normal human to be able to manouevre!
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Old 08 December 2010, 15:22   #7
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thanks to all for the input.
the tohatsu looks interesting, but a little to expensive, and in ireland. the 15 with fins added should do the trick it seems as i have never seen the elusive late 20hp in a year of consistent looking and the 25 is to powerful for my 20hp rated futura... would it be to dangerous to put a 25 on ?
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Old 08 December 2010, 15:38   #8
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... would it be to dangerous to put a 25 on ?
If it has a 20hp rating then its there for a reason, secondly putting on a 25hp would invalidate your insurance.

Hope you've got insurance

Jake
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Old 08 December 2010, 15:51   #9
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as we launch with transom wheels over the beach and the boat is small with a 10 hp i dont have insurance. is this really a problem? how many insurance companies are there taking money of us all of the time. if we do use a slipway occasionaly the insurance has been included in our launch fee
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Old 08 December 2010, 16:35   #10
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hey dogboy, i had a 15hp 4 stroke suzuki (2 yr old) on my 3.1mtr inflatable boat, fab engine and very frugal on fuel! also very versatile as can be put on other boats from fishing boat to inflatable.
its for sale at a sensible price if you intrested?
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