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Old 28 October 2017, 13:43   #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, 14:37   #2
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Go for it
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Old 28 October 2017, 14:55   #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, 12:37   #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, 14:00   #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, 14:14   #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, 17:23   #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, 02:46   #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, 04:39   #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, 06:26   #10
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You'll be fineIf you're worried, just buy some 40hp stickers


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Old 19 November 2017, 08:26   #11
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problem solved a just brougt i set of carbs from a 50hp off ebay ! that should do the trick
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Old 19 November 2017, 08:54   #12
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i had over powered (between 10-40hp over) boats for years, insurance was reasonably straight forward back then, it put the price up ofcourse but so long as you have it in writing the size of the engine on your policy and you tell them you have exceeded the maximum recommended then you have done all you can.

if you have an accident and there is evidence you have exceeded the maximum hull speed permitted then you may have a problem but normal theft shouldn't be a problem.

this is a topic best discussed with your own insurance company and not left to chance on the interweb though.
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Old 19 November 2017, 10:06   #13
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Just had a customer who had an ďaccidentĒ with a dock and claimed damage to his tube from it. The inspector for insurance was very thorough and checked everything . Capacity plate and motor along with many photos. She even checked to see if motor weighed too much for the boat. Definitely was the most thorough inspection I have ever seen by insurance company.
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Old 19 November 2017, 11:45   #14
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I repowered a searay sundancer from 2x 165hp diesels to 2x300hp diesels the largest engines searay fitted to the boat was 2x260hp petrols i got a survey report stating the installation was acceptable sent it to the insurance company and they never quibbled
I would always make the company aware though as you would expect them to use it as a get out clause if the shit hit the fan
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Old 19 November 2017, 11:48   #15
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problem solved a just brougt i set of carbs from a 50hp off ebay ! that should do the trick
Nahh a 50 hood and data plate was the answer
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Old 19 November 2017, 15:29   #16
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Completely agree with insurance checking everything to the dot, if it's proven you falsely tried to deceive the insurer in any kind of accident you'd better hope you don't own any assets when you get sued. If it's a public liability case where you've injured someone be prepared to do time too.
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Old 19 November 2017, 15:31   #17
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Just to further add, any investigation into a serious claim could find its way back to you knowingly and willingly talking about it on this public forum.
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Old 19 November 2017, 16:59   #18
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Just to further add, any investigation into a serious claim could find its way back to you knowingly and willingly talking about it on this public forum.
Nothing wrong with discussing it on here the question has been asked and so far is not answered is it an offence / does it void insurance if you overpower a boat so far no definitive answer
Clearly my post regarding a 50 hood was tongue in cheek following my previous cautionary post
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Old 20 November 2017, 03:49   #19
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Completely agree with insurance checking everything to the dot, if it's proven you falsely tried to deceive the insurer in any kind of accident you'd better hope you don't own any assets when you get sued. If it's a public liability case where you've injured someone be prepared to do time too.
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Just to further add, any investigation into a serious claim could find its way back to you knowingly and willingly talking about it on this public forum.
Not sure who the comment was directed at, but I am sure you have read the whole thread. The OP is not deceiving anyone, he has downgraded his engine so it only outputs 50HP and is therefore within spec. The alternative would have been to be open to the insurer that his boat had a 70HP engine on it, which at least in the UK others have done in the past without issue.

As for "doing time" I'm sceptical. Especially since in the OP he was clear his intention was never to see if he could drive it maxxed out. Of course even with an underspecced engine he could still end up the wrong side of the law if he drives it dangerously, but its not obvious what the imprisonable offence would be for doing the opposite?
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Old 20 November 2017, 12:52   #20
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I'm more interested in how 50hp carbs are going to fit onto a 70hp and run when it's a totally different engine.
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