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Old 10 September 2010, 17:26   #1
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Newbie!!!!! What HP advice?

I am new to Sibbing and have recently bougth a Prowave 320 Airdeck ( i know its a generic import and no match to the avon or zodiac)

It is rated to take a 15hp but i read somewhere that a 15 and a 20 weigh the same and i also read on rib net another bit of advice to a newbie that it is better to go bigger and not use full power.

so is it better to ignore the rules and get a 20hp

Any suggestions welcome.
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Old 11 September 2010, 01:48   #2
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Quote:
Originally Posted by lockieboi View Post
I am new to Sibbing and have recently bougth a Prowave 320 Airdeck ( i know its a generic import and no match to the avon or zodiac)

It is rated to take a 15hp but i read somewhere that a 15 and a 20 weigh the same and i also read on rib net another bit of advice to a newbie that it is better to go bigger and not use full power.

so is it better to ignore the rules and get a 20hp

Any suggestions welcome.
Hi there just my opinion but it comes down to could you/should you?

answer = yes/no

Yes you could put a 20hp on, but should you?

Do you have insurance? You'd be an idiot not to, not just for theft etc but the 3million liability is essential, and all for roughly 60-70. So if you have insurance and then decide to put on an engine above the manufacturers stated rating, is your insuarnce valid? Will they pay up when something goes wrong?

Simply No. If you want a bigger engine then change the boat.

Best wishes

Jake
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Old 11 September 2010, 03:10   #3
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No 15 hp motor weighs the same as a 20 hp.

They use a different block. 6 is shared with the 15, and 20 is shared with the 25, with most manafactuers, the weight's being the same between each model respectively.

Not so much power, but weight is important. Yes you can have more power, and it will be fine, provided you don't drive in a manner that will upset the handling of the boat, and do not operate the boat at speeds unsuitable for the conditions.

The weight however, will have a noticible impact on the way the boat handles and performs, and you especially do not want to fit a motor any heavier than what the transom is rated at. Also consider insurance as mentioned above, and any manafactuer warranty on the hull itself, that can be voided.

A 320 hull, with a 15 will get along very well, especially one up, and still perform reasonably well 2 up.

I wouldn't reccomend going any larger than the 15, unless you plan or carrying a fair bit of weight, along with a bit of exp. Even within the reccomendations, an in-experienced or careless operator, can still end up in hot water. (or very cold water in your case UK...)

As your new to sibbing, i definately reccomend staying within all of the manafactuer's recomendations, atleast until you familiarise yourself with the boat, boating in general, rules, and so forth.

BB
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Old 11 September 2010, 03:40   #4
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No 15 hp motor weighs the same as a 20 hp.

They use a different block. 6 is shared with the 15, and 20 is shared with the 25, with most manafactuers, the weight's being the same between each model respectively.
That's a very bold statement BB, you suggested something similar recently on another thread. I'm no engine expert but the most basic search reveals that you're talking, well, complete nonsense.

See Yamaha specs attached.
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Old 11 September 2010, 03:43   #5
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His current motor is a 2 stroke, and unless someone specifically states that he/she is looking at a 4 stroke, then i have little reason assume otherwise. That chart you have just provided us with is for the 4 stroke range of portables.

I guess i could have been more specific, but i woudln't give the advice of buying a 115lb 15 hp motor to be used on a SIB.....

And i did say, as with "most manafactuers" yes some differ, i know that Yamaha do not share the same cu di between the 6 and the 15, rather the 6 and 8 are different, and the 9.9 is shared with the 15, and yes the year of the model will make a difference also...
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Old 11 September 2010, 03:54   #6
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Thanks for all the advice, some very valid points.
Perhaps I will stick with the manufacturers recommendations and defiantly look at insurance.
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Old 12 September 2010, 10:38   #7
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FYI.

i have a 3.5m rib and it goes well with 15hp on it. about 23mph wot. thats 2 up and 20ltrs fuel.
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Old 12 September 2010, 11:25   #8
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Quote:
Originally Posted by lockieboi View Post
It is rated to take a 15hp but i read somewhere that a 15 and a 20 weigh the same and i also read on rib net another bit of advice to a newbie that it is better to go bigger and not use full power.
I wouldn't assume that all advice on Ribnet is necessarily good advice! There are some people on Fibnet who are obsessed with how fast their boat is - and bragging about how many horses they have is all part of the same mantra. Apart from causing you warranty and insurance problems, the boat might simply be scary to use with too much power (although only 5HP extra it is 33% "over" the advice of the manufacturer).

Quote:
Originally Posted by willk
I'm no engine expert but the most basic search reveals that you're talking, well, complete nonsense
now, what was it you said the other day about diplomacy?

You are of course right - and google tells us that Mariner and Tohatsu 4 strokes at 15 and 20 HP are also the same weight, and heavier than their sub 10HP cousins...

Quote:
Originally Posted by busboy
His current motor is a 2 stroke, and unless someone specifically states that he/she is looking at a 4 stroke, then i have little reason assume otherwise. That chart you have just provided us with is for the 4 stroke range of portables.
except that 2 strokes are no longer available ("with the exception of new tech 2 strokes - which AFAIK is only available as an Etec in this size range - and makes the 4 strokes seem like lightweights!). So unless someone specifically says that are looking for a 4+ yr old engine then its probably reasonable to assume they are talking 4stroke at this size.

Quote:
Thanks for all the advice, some very valid points.
Perhaps I will stick with the manufacturers recommendations and defiantly look at insurance.
I'd say you'll be fine with 15 HP, no point paying the extra pricetag for 5HP you "never plan to use".
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Old 12 September 2010, 13:09   #9
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now, what was it you said the other day about diplomacy?
...it was getting to me
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