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Old 28 October 2017, 14:43   #1
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Excessive Power

Hi I have recently bought a 4.2 Zodiac Pro for dive purposes and I was considering stripping my speedboat and using the 70hp Mercury for the Zodiac.
The Zodiac is rated at 40 but surely this must be purely down to power and not weight as the Mercury is only 80k.
The horsepower seems excessive but I was thinking of winding in the throttle stop at the engine, has anyone else out there had the similar circumstances
Thanks Mike
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Old 28 October 2017, 15:37   #2
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Go for it
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Old 28 October 2017, 15:55   #3
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You donít have to push the throttle all the way.

Every over powered boat I had just had too much unbalanced weight.

I wouldnít hesitate if you know the 70 is a good reliable motor that fits in the weight limit of the hull. Why buy an unknown history outboard if you have a perfectly good one.

And then there was my lightweight aluminium 5.6m Dockitjet with 200hp that started to chine walk until the tube separated from the hull. The hull that didnít float all that well without tubes. All I will say is donít exceed the designed hull speed by too much.
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Old 18 November 2017, 13:37   #4
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You donít have to push the throttle all the way.

Every over powered boat I had just had too much unbalanced weight.

I wouldnít hesitate if you know the 70 is a good reliable motor that fits in the weight limit of the hull. Why buy an unknown history outboard if you have a perfectly good one.

And then there was my lightweight aluminium 5.6m Dockitjet with 200hp that started to chine walk until the tube separated from the hull. The hull that didnít float all that well without tubes. All I will say is donít exceed the designed hull speed by too much.
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Old 18 November 2017, 15:00   #5
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Just keep in mind that if things go pear shaped any investigation will focus on manufacturers recommendations & you may be required to justify your actions in court.
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Old 18 November 2017, 15:14   #6
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I know what you mean , but the 70 is 25 kilo lighter than a 40hp four stroke , and being 37 years old it must have lost a few pony's over the years !
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Old 18 November 2017, 18:23   #7
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Just keep in mind that if things go pear shaped any investigation will focus on manufacturers recommendations & you may be required to justify your actions in court.
I'll second that. Being over the rating of the hull also means you are uninsured, even if you get an insurance, the insurance company will use that as a legal get-out to stick the boot into you. Don't do it.
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Old 19 November 2017, 03:46   #8
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You'll be fineIf you're worried, just buy some 40hp stickers
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Old 19 November 2017, 05:39   #9
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I'll second that. Being over the rating of the hull also means you are uninsured, even if you get an insurance, the insurance company will use that as a legal get-out to stick the boot into you. Don't do it.

That rumour circulates from time to time. Every time it does, nobody can cite a single case where it has definitely happened, and yet people have definitely made claims where it has not been a problem.

It would obviously be wise to tell your insurer the actual size, but if youíve adjusted the max power throttle stop it wonít be 70hp.
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Old 19 November 2017, 07:26   #10
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You'll be fineIf you're worried, just buy some 40hp stickers


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