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Old 03 July 2016, 13:48   #1
Member
 
Country: Spain
Boat name: Aquaholics
Make: Valiant
Length: 4m +
Engine: 40hp johnson
Join Date: Jul 2016
Posts: 10
Outboard engine height

Hi guys
I'm new to this so I hope I've posted in the right place.
Anyway I've recently got a 4m valiant rib and a mate gave me a 40hp Johnson 2 stroke.
Got it all set up and when I took it out on the med it will not plane.
I mean as I open up the throttle It picks up speed but then the revs max out and the rib slows.
I don't think the outboard is sitting in the water enough and starts taking air (maybe)
The ac plate is level with the water when this happens.
I have noticed the ac plate is higher than bottom of the rib but i can't drop it any more.
Help please guys as it's the summer and need to get out on the sea.
Thanks
Matt from spain
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Old 03 July 2016, 14:40   #2
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Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Mercury
Length: 3m +
Engine: Suzuki Outboard/25/4
MMSI: 235074042
Join Date: Oct 2011
Posts: 3,573
You have a short shaft engine Matt for a 15 inch transom your transom will be 20 inch long shaft engine required
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Old 03 July 2016, 15:05   #3
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Country: Spain
Boat name: Aquaholics
Make: Valiant
Length: 4m +
Engine: 40hp johnson
Join Date: Jul 2016
Posts: 10
Well that's just great.
I've spent a small fortune on the outboard.Is there anyway of sorting it apart from cutting the transom which I don't really want to do?
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Old 03 July 2016, 15:07   #4
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Country: Spain
Boat name: Aquaholics
Make: Valiant
Length: 4m +
Engine: 40hp johnson
Join Date: Jul 2016
Posts: 10
What sort of boat would this engine go on just out of intrest?
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Old 03 July 2016, 15:12   #5
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Country: UK - England
Town: East
Boat name: Seaflyer
Make: Humber
Length: 6m +
Engine: Evinrude
Join Date: Feb 2014
Posts: 199
A short shaft engine would fit possibly on a SIB.
You might be able to get something like this: -
Johnson Evinrude Extension Kit #379877 #378798 40 HP 1960s - 70s * L O O K | eBay
Good luck
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Old 03 July 2016, 15:19   #6
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Country: UK - Scotland
Town: Denny
Boat name: Hebridean Storm
Make: Coastline
Length: 6m +
Engine: Honda 130hp
MMSI: 235107505
Join Date: Mar 2013
Posts: 841
Quote:
Originally Posted by Matspain View Post
Is there anyway of sorting it apart from cutting the transom which I don't really want to do?
Sorry but not an option,
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Old 03 July 2016, 15:27   #7
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Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Mercury
Length: 3m +
Engine: Suzuki Outboard/25/4
MMSI: 235074042
Join Date: Oct 2011
Posts: 3,573
As tango says don't cut anything try and get a leg extension or its part ex for a long shaft.

Cheers
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Old 03 July 2016, 15:42   #8
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Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: reiver 3.8/regal3760
Length: 10m +
Engine: 40hp 2st 2x6lp 315
Join Date: Jul 2009
Posts: 1,502
If you've got a good engine and your going to keep the boat cut the transom and go boating.
I've got a 40 yam short shaft on my little 3.6m rib and it's fine keeps the centre of gravity low and doesn't cause any problems at all
If you think you might want to upgrade the engine in the near future then maybe a bad idea to cut the transom but if the engine is likely to stay with the boat then absolutely nothing wrong with a short shaft engine on a small rib
I owned mine for 15 years and use it for all manner of things from diving to waterskiing with no problems at all
Mine runs 2"high so only dropped the transom by 3"
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Old 03 July 2016, 16:51   #9
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Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 60hp + aux
MMSI: 235087213
Join Date: Jun 2007
Posts: 3,270
RIBase
Out of interest, how is that enging secured? Only looks like the bottom two bolt holes are being used?

Get a long-shaft engine and sell in the standard shaft. Cut the transom and you'll ruin the boat. Just my tuppence worth.
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Old 03 July 2016, 17:54   #10
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Country: UK - Scotland
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Length: 10m +
Engine: 40hp 2st 2x6lp 315
Join Date: Jul 2009
Posts: 1,502
Presumably secured with the thumb screw clamps
Can someone explain what the big problem is with cutting the transom, I don't see the issue if the engine is to remain on the boat long term
Back in the 70's & 80's many boats were built as short shafts engines up to 70hp were available as short (or more correctly standard shaft)
My pal raced a power boat with an 85 yamaha converted to short shaft to lower c of g I've been running my rib 15 years with a short shaft
The boat in the picture doesn't look like it's in the first flush of youth & the op already has an engine he's spent good money on
OK in an ideal world he would buy a long shaft but depending on budget that could be fraught with problems let alone the time it may take to find the correct engine then fit it and hope it actually works once in the water
Cutting the transom he's out on the water enjoying his boat immediately
It's a no brainer to me
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