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Old 12 April 2008, 17:23   #1
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175 for 150?

Swapping a 175 opti for my 3 year old 150, will I notice any difference? How much? In accelleration? In WOT?

What about a 200?

Thanks

Bruce
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Old 12 April 2008, 17:57   #2
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Yes
16%
Yes
Yes

33%

Now for the interesting bit you haven't asked about... the handling.

The 175 will make the RIB handle no differently as it's essentially the same engine as the 150 (except that the increased acceleration may make the handling feel better) but the 200 will have a detrimental affect as the RIB will be more tail heavy, so it'll lift the nose more in a head sea and come down tail heavy more in a following sea.

So if you've spent the last couple of years blasting around on a flat Solent, the 200 is the way to go. If you've been going as fast as you can through rough seas, the 175 may have a big advantage for you.
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Old 12 April 2008, 18:52   #3
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Ok Anecdote from Jono. 135 and 175 on similar boats and the difference in performance is about 5 or 6 knots (from a base of I guess 40) - I am quoting from memoory here.

On your calc, that should be (if the maths is right) 11 or so knots. Why half of what expected?

If I can get from gps 2way properly done 43/44 on my 150 to a 16% speed increase, gr8. If I get 3/4 knots why bother?
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Old 12 April 2008, 19:10   #4
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'cos all I've done is compare HP... which is academic. Jono's anecdote sounds sensible, but it's all based on that "similar" word... were there any other differences?

The difference in speeds is all down to the laws of physics... it's a classic case of E=MC2 (Can VBulletin do superscript?)

The important question here is what exactly do you want? Do you have specific speed you want to reach? Do you want to just go as fast as possible? If that's the objective, just order an ETEC 300.
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Old 13 April 2008, 04:51   #5
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Why don't you ask a Solent owner that has a 200 on the back, that'll give you a much more accurate Idea of performance in terms of top speed and handling.
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Old 13 April 2008, 06:09   #6
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Bruce, the Commodore of Portsmouth Sailing Club has a 6.5m Solent with a 150 opti on the back. Might be worth emailing him and asking him about performance if your still interested in the 150. His email address on is on the PSC website.

Edit: I should have read this thread properly. You already have a 150 so the above is of no use at all! For some reason I thought you currently had a 175....
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Old 15 April 2008, 19:31   #7
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Quote:
Originally Posted by brucehawsker View Post
Ok Anecdote from Jono. 135 and 175 on similar boats and the difference in performance is about 5 or 6 knots (from a base of I guess 40) - I am quoting from memoory here.

On your calc, that should be (if the maths is right) 11 or so knots. Why half of what expected?

If I can get from gps 2way properly done 43/44 on my 150 to a 16% speed increase, gr8. If I get 3/4 knots why bother?
Because, for a given increase in power, you'll generally only get half of that in terms of proportional speed increase, so Jono's anecdotal figures make sense.
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Old 16 April 2008, 13:00   #8
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I had a 6.5m Crompton - 52mph @ wot with a 150, 60mph with a 200, approx increase of 15%
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Old 16 April 2008, 15:23   #9
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I have a 150 hp Opti on my Solent 6.9 but in hindsight should have got the 175 Opti just for that little bit of extra grunt maybe upgrade later
Have a 200 Etec on my other Solent 6.9 and it has a much bigger wow factor
The Jackeens have a 200 Etec on their 6.5 have a chat with them as they have same size boat as you .
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Old 20 April 2008, 09:46   #10
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It goes quite well with the 150 Bruce!
I wouldn't think you would notice that much of a difference with the 175, certainly not enough difference to constitute the additional outlay.
200HP would give the grin factor but it may upset the handling slightly, it seems relatively well balanced at present and a good overall package.
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