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70 footer inboard to outboard conversion - madness?

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70 footer inboard to outboard conversion - madness?

Old 10-08-2019, 03:45 PM
  #21  
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Default 48 jarrett

Thanks, this is exactly what I was looking for : not quite 70 yet but definitely something. I will try to find more.

https://www.jarrettbay.com/carolina-...achts/hull-20/

thanks to all for the contributions, seems disturbing to some but not all
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Old 10-08-2019, 04:01 PM
  #22  
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Default Why outboard at such a cost...

as an answer to some questions: there are some places in Europe where inboard maintenance is just about being available for regular abuse from mechanics, like purposely getting engines to break just for additional work etc. (Happened to me already)

At the end of the day, outboard boating for me is about trust that one will enjoy boating rather than worry about the next scam
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Old 10-08-2019, 04:12 PM
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Originally Posted by KR98 View Post
There was a thread on here a while ago, 48' Jarrett
Aw yes the stripper pole boat
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Old 10-08-2019, 04:32 PM
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A 70’ er isnt going to behave like she was built to behave without diesels in her belly.
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Old 10-08-2019, 05:15 PM
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Some issues to think about (not exhaustive by any means):

1. Any 70’ ish sportfish is going to have around 3500-4000hp in twin diesels. Just replicating that power in outboards will be difficult and expensive.

2. Effect on COG and subsequently stability etc will be severe.

3. Converting the diesel fuel system to gasoline - wouldn’t even begin to guess at what that might entail.

4. Do they make outboards with long enough legs to reach clean water on a big sporty?
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Old 10-08-2019, 05:17 PM
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Hey Go for it. Thats what money is for, being first to try something everyone says is impossible.
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Old 10-08-2019, 05:20 PM
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If you put quad outboards on an old heavy 70' hull, wouldn't the props just cavitate when you try to throttle up? Can you put big enough wheels on them to get that kind of weight moving?
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Old 10-08-2019, 05:20 PM
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I saw a 48 Fountain EC that had been converted to OB's, looked like it ran pretty good
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Old 10-08-2019, 05:34 PM
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Nothing 4 or 5 seven marine 627’s wouldn’t take care of.
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Old 10-08-2019, 05:39 PM
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Just use (5 or 6) 7 marine 627 motors with Duoprop setups! Pretty sure you will get anything up on plane and moving. Sport fish style boats typically don't seem to draw much water in the stern so outboards could reach clean water off a bracket no problem.
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Old 10-08-2019, 05:42 PM
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1800 HP isnt nearly enough for a 70 footer. That boat will weigh twice what that JB does easily.

The JB with the stripper pole did 46 WOT with quad 350's. But it was purpose built from the ground up. A ship pilot owns it.
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Old 10-08-2019, 05:43 PM
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Originally Posted by jgren View Post
Just use (5 or 6) 7 marine 627 motors with Duoprop setups! Pretty sure you will get anything up on plane and moving. Sport fish style boats typically don't seem to draw much water in the stern so outboards could reach clean water off a bracket no problem.
a bracket with 3,600+ HP. Rrrrrright
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Old 10-08-2019, 05:43 PM
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Originally Posted by Pierre_l View Post
understood

what is the biggest boat ever converted so far - sound like bertram 35 or so have been done?
64’ Viking

64' Viking with twin outboards....
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Old 10-08-2019, 05:46 PM
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Originally Posted by fireisland1 View Post


a bracket with 3,600+ HP. Rrrrrright
Nothing a little bracing won't take care of.
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Old 10-08-2019, 05:49 PM
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Originally Posted by jgren View Post
Just use (5 or 6) 7 marine 627 motors with Duoprop setups! Pretty sure you will get anything up on plane and moving. Sport fish style boats typically don't seem to draw much water in the stern so outboards could reach clean water off a bracket no problem.
This is what would be required. But $5-600k sure would buy a nice sporty with diesels in it.
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Old 10-08-2019, 05:50 PM
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Originally Posted by alwhite00 View Post
Nothing 4 or 5 seven marine 627’s wouldn’t take care of.

now were talking...
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Old 10-08-2019, 05:54 PM
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Originally Posted by jgren View Post
Just use (5 or 6) 7 marine 627 motors with Duoprop setups! Pretty sure you will get anything up on plane and moving. Sport fish style boats typically don't seem to draw much water in the stern so outboards could reach clean water off a bracket no problem.
Enough hp on an Armstrong bracket would likely do it.
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Old 10-08-2019, 06:03 PM
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Originally Posted by jgren View Post
Just use (5 or 6) 7 marine 627 motors with Duoprop setups! Pretty sure you will get anything up on plane and moving. Sport fish style boats typically don't seem to draw much water in the stern so outboards could reach clean water off a bracket no problem.
Makes sense. You’re at around $500k or so just in bare engines before conversion, rigging etc.
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Old 10-08-2019, 06:04 PM
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I would like to clarify some wrong information here in this post.

Jarrett Bay built the Razorback Express as an inboard express boat. It was bought a few years ago and converted to the blue boat that you see on these pages. This work was not done by JBBW. It was not purposely built that way. Jarrett Bay had nothing to do with what it has become.

My momma told me that if you can’t say anything nice....

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Old 10-08-2019, 06:05 PM
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Originally Posted by Locke N Load View Post
This is what would be required. But $5-600k sure would buy a nice sporty with diesels in it.
It would also buy a lot of maintenance and upkeep on a set of diesels already in the boat.
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