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Old 02 September 2012, 16:12   #11
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Country: UK - Scotland
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Quote:
Originally Posted by pluto2 View Post
The engine is Merc 90 four stroke spinning a 13x21 prop. When powered up to 30 knots and over, it gets a bit unnerving coming off a wave and down on to your port tube. The hull is in good shape, cant see anything odd about it, just wondering why this is happening, anyone else experience it I wonder ?
Its an offset issue ... you dont have enough of it The worst hull that did it for me was an 8.5,.. and 40 gallons of contained water inboard and on the starboard side would'nt cure it

If its as bad as you say with only a 90 .. it would suggest little or no offset at all.. can you measure the position of your engine on your transom ie how much off centre it is, and report back ?
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Old 02 September 2012, 17:01   #12
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Is your outboard too deep in the water?

I have this same problem with my 5.8 RIB and Suzuki DT200 running a 25 pitch prop only a lot worse. It hits the water so hard that it feels as if the tube will rip off.

My engine looks a lot deeper than it should but I can't lift it anymore so I need major surgery to fix it and that will be the project over the next few months. I hope it will work for me.
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Old 02 September 2012, 17:15   #13
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Country: Ireland
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Hi Bigmuz7,
Thanks, I'll check that in the next couple of days, but from what I think its in the dead centre of the transom, I had never heard of off before now,
Pluto2
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Old 02 September 2012, 17:19   #14
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Hi Kubcat,
Yes, the engine is mounted right down on the transom, no space above it, I had never thought there shoulb be till now.
Pluto2
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Old 02 September 2012, 17:20   #15
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two components....engine needs to be offset to the right. A 90 may be small to some peeps on here but once it would have been thought of as quite a beast. In the past I've had exactly the same issue with a 35hp Volvo Penta!!
The trim tab is unlikely to have any noticable affect, they've never done any good for me.
Second component may be driver error. The trim setting needs to be right at speed. It is surprising how many boat owners think the trim switch is just an on/off thing
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Old 02 September 2012, 17:24   #16
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Country: Ireland
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Hi Wavelength,
When you say offset to the right, do you mean to starboard or port?
And yes you could be right , my management of the trimming switch wouldnt be the best Id say as I havent much experience of this RIB(Only got it a few months ago)
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Old 02 September 2012, 17:35   #17
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RIBase
Definitely an off-set issue (my opinion)! If you are running a normal rotation engine (prop spinning clockwise) then the engine will naturally tip the boat to the port (left) hand side. If your engine is in the centre of the transom, you will get a lean on the boat at higher speeds. Some pics would be useful!!!
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Old 02 September 2012, 19:27   #18
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starboard for the usual clockwise rotational prop.. always offset in the direction of rotation.
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Old 02 September 2012, 19:45   #19
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Quote:
Originally Posted by wavelength
starboard for the usual clockwise rotational prop.. always offset in the direction of rotation.
I missed that it was starboard, mine slams to port so maybe a different issue.
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Old 03 September 2012, 15:28   #20
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no it leans to port I think he said
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