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Old 01 November 2016, 13:21   #1
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70hp on an Avon SR4?

Hi there, just bought my first rib, avon sr4, just doing some work to her before i take her out, hopefully in the next couple of weeks, only slight concern is the engine (evinrude 70hp) - slightly over powered - been told as long as i am sensible it will be fine, the transom will be OK, good condition, any advice would be greatly appreciated, thanks alex
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Old 01 November 2016, 15:09   #2
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Hi
70 HP on a SR4 with the original transom will NOT be fine. Besides, you have no idea of telling(exept drilling) if the transom is slightly wet.
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Old 01 November 2016, 15:15   #3
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Thanks for your useful input
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Old 02 November 2016, 08:16   #4
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Welcome to RIBnet Alex r, some of the SR4 nutters will be along shortly to assist. They know their stuff - have a think about their replies. I've moved your post to increase it's exposure a bit.

w.
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Old 06 November 2016, 13:30   #5
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Quote:
Originally Posted by willk View Post
...some of the SR4 nutters will be along shortly to assist...
...or maybe not!

You've communicated to me by PM that your engine is a 1981 and possibly well under 70hp in actual output. No harm, 70hp is a lot to dial into an SR4 - they can get dangerously squirrelly with a 50hp, being prone to chine walking at higher speeds.

Older SR4s can have issues with weakened/rotten transoms. Applying a lot of power through one such as that will likely end in unhappiness. I presume you've had your transom checked for wet timber/movement?

Obviously we'd all be interested to hear how the 70hp Evinrude runs on your RIB.
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Old 06 November 2016, 14:09   #6
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A older 70 is overweight and overpowered, not a good recipe dude.personally i wouldn't.
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Old 06 November 2016, 14:13   #7
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Originally Posted by willk View Post
...or maybe not!

You've communicated to me by PM that your engine is a 1981 and possibly well under 70hp in actual output. No harm, 70hp is a lot to dial into an SR4 - they can get dangerously squirrelly with a 50hp, being prone to chine walking at higher speeds.

Older SR4s can have issues with weakened/rotten transoms. Applying a lot of power through one such as that will likely end in unhappiness. I presume you've had your transom checked for wet timber/movement?

Obviously we'd all be interested to hear how the 70hp Evinrude runs on your RIB.
excuse my ignorance but whats chine walking
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Old 06 November 2016, 14:18   #8
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going to be a crazy fun boat until it goes wrong tho . seriously I wouldn't be running it flat out if It was mine it may out perform the hull and turn into a bit of a handful .steady away and it may be fine
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Old 06 November 2016, 14:21   #9
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excuse my ignorance but whats chine walking
When at speed it jumps left to right. with that hull design it generally can start at 36 knots if weights and balance dictate.
an ideal weight and engine size is a lightweight 40hp - 50hp max
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Old 06 November 2016, 15:30   #10
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When at speed it jumps left to right. with that hull design it generally can start at 36 knots if weights and balance dictate.
an ideal weight and engine size is a lightweight 40hp - 50hp max
ah gotcha had that on my old brig I think it was quite bad if the motor wasn't trimmed up enough
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