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Old 19 February 2009, 15:35   #1
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Bigger engine than Rated

Hi all,

My 4m rib is rated to a 40hp. Ive got a 1990 40hp mariner 2 stroke engine, can i put a 2005 50hp johnson four stroke engine on the back?

Thanks
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Old 19 February 2009, 16:41   #2
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I think it comes down to the weight of the engine Ali but them more experienced will be able to tell you more. I will say from experience, insurance can be a bit of a pain.
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Old 19 February 2009, 17:01   #3
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I think it comes down to the weight of the engine Ali ...
If that were the case, then the boat would come with a max weight limit for the motor, rather than a max hp (or both)
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Old 19 February 2009, 17:09   #4
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If that were the case, then the boat would come with a max weight limit for the motor, rather than a max hp (or both)
There you go, you know better than me. Was only going of what you and others have said before about the weight being more important. Will bow out
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Old 19 February 2009, 17:33   #5
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Part of the question may relate to how much spare underwear is available
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Old 19 February 2009, 18:06   #6
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.. Was only going of what you and others have said before about the weight being more important...
I don't recall this.

What did I say on the subject?
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Old 20 February 2009, 03:28   #7
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Taking that weight / HP argument to the logical conclusion, my 1970s vintage hull is plated for 60Hp, no mention of weight. Back then most engines were properly lighter, as a 2 cyl premix was the norm for that ballpark HP. The transom isn't plated for weight, so in theory I could hang a hypothetical nice new 60Hp 4- stroke that weighs in at 170Kg on it.

One call to Humber they confirmed it was rated to 110Kg (which would have been more than enough for any 60 or pair of 30s of the era)


Technical arguments aside, your insurance salesman will be rubbing their hands all the way to their annual bonus if you exceed the ratings!
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Old 20 February 2009, 04:15   #8
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thanks for your help everyone, i've decided ive got to find out what the maximum weight the boat can take. Does anyone know how i can get hold of the makers of Ocean Ribs.
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Old 20 February 2009, 04:27   #9
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I don't recall this.

What did I say on the subject?
There's lots of threads on the subject of moving to 4 stroke which more HP from a 2 stroke mate. Some of which you've joined in. I wanted to stick a 50/60 hp 4 stroke on a SR4 and was advised against it. Chill

But like I say, I'll bow out of this one as I really don't know much about the subject. Always use the collective knowledge of this forum and you have let me tap in to your knowledge so much I owe you far to many pints. The 703 springs straight to mind
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Old 20 February 2009, 04:29   #10
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thanks for your help everyone, i've decided ive got to find out what the maximum weight the boat can take. Does anyone know how i can get hold of the makers of Ocean Ribs.
http://rib.net/forum/showthread.php?...ght=Ocean+ribs
going off the above link they are from Windsor Marine?
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Old 20 February 2009, 04:31   #11
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http://rib.net/forum/showthread.php?...ght=Ocean+ribs
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Old 20 February 2009, 05:39   #12
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Is the max engine output on a boat linked to the CE markings on the plate.

In other words the boat is only issued with a CE plate if the engine dose not exceed X horsepower you may find that by changing the engine the boat may not be CE compliant.

But it may be as simple as weight but if it was then you would have a max weight on the CE plate not max hp.
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Old 20 February 2009, 07:25   #13
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There's lots of threads on the subject of moving to 4 stroke which more HP from a 2 stroke mate. Some of which you've joined in. I wanted to stick a 50/60 hp 4 stroke on a SR4 and was advised against it....
While I may have joined in a debate or two on 2 stroke v 4 stroke, I don't recall advising anyone that fitting a motor more powerful than recommended would be acceptable.
DHD (chilled )
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Old 20 February 2009, 08:40   #14
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While I may have joined in a debate or two on 2 stroke v 4 stroke, I don't recall advising anyone that fitting a motor more powerful than recommended would be acceptable.
DHD (chilled )
No I've never read that statement from you. Only advice to watch the extra weight on the transom.
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Old 20 February 2009, 09:14   #15
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How old is the boat it'll be fitted on? I'm thinking it'd be a really bad idea to overpower a boat with a 4 stroke if the boat was built when 4 strokes weren't widely available.

I''m not saying overpowering is a good idea-but it'd be far worse to add weight the boat is likely not designed for plus overpowering it by 25%.

Personally, I wouldn't do it anyway.
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Old 20 February 2009, 10:30   #16
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Quote:
Originally Posted by ali_seton View Post
Hi all,

My 4m rib is rated to a 40hp. Ive got a 1990 40hp mariner 2 stroke engine, can i put a 2005 50hp johnson four stroke engine on the back?

Thanks
How many would you ask for the Mariner?
Is it a 6E9? Longleg?

Mike
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Old 20 February 2009, 12:22   #17
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How many would you ask for the Mariner?
Is it a 6E9? Longleg?

Mike
im looking for around 1199 as it has new top engine mounts
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Old 20 February 2009, 12:23   #18
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How old is the boat it'll be fitted on? I'm thinking it'd be a really bad idea to overpower a boat with a 4 stroke if the boat was built when 4 strokes weren't widely available.

I''m not saying overpowering is a good idea-but it'd be far worse to add weight the boat is likely not designed for plus overpowering it by 25%.

Personally, I wouldn't do it anyway.
the boat was built in 2002 or 2003
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Old 21 February 2009, 11:01   #19
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thanks for your help guys...

i looked at those links you sent me and made a few phone calls to dealers of ocean ribs and some people who make them. They say that the maximum rating is a 50hp but it is reccommended to a 40hp, so they said that the johnson would be fine.

Im still not 100% sure that i feel happy putting that engine on the back. ill do some more homework and make some more calls!

thanks everyone
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