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Old 14 April 2008, 06:06   #1
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Country: Germany
Make: RIBCRAFT 5.85
Length: 5m +
Engine: 150AETX Yamaha
Join Date: Mar 2004
Posts: 86
Ribcraft 5.85 with 150 Yamaha 4 Str.

Hi there,

need your help /advice please. I'm thinking about to buy some new 150hp Yammi instead of the one i got now (100hp Yammi). The transom of the boat is cut to XL-Shaft (508mm, 20''). So, should i buy 150hp with XXL (635mm 25'') and change the transom to 636mm (25''), what will cost a lot of work and money or will the boat work fine with a 150hp, 20'' on the back?
Maybe here are some owners of this combination:
5.85 with 150hp 25'' or 5.85m with 150hp 20'' on the back.

TXS a lot

Oliver
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Old 14 April 2008, 06:40   #2
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Country: Netherlands
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Make: Brig F360S
Length: 3m +
Engine: Yamaha 70hp
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Lower transom = engine lower to water = point of rotation lower
Higher transom = engine higher to water = point of rotation higher

With a high transom theoretically the boat will fall more from left to right than with a lower transom, so more chinewalking. But I don't know if that theory does apply in real world boat setups.
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Old 14 April 2008, 07:23   #3
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Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,298
Stick with 20" (Longshaft actually - XL is 25")
As you say, there'd be a lot of cost and work involved in adapting the transom to 25" and it wouldn't be as sturdy as a 25" transom from the factory.
Your new engine will be heavier than the old one, so you may have issues with the balance of the boat and the stern will sit lower in the water. You may also have some (more) backwash coming over the transom when she comes off the plane. If this is a problem, consider a (bigger) bilge pump to clear the deck.
Have you considered lighter ways of getting more power? Soozook 140, Optimax 150, etc?
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Old 14 April 2008, 07:41   #4
DJL
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Make: Ribcraft 6.5
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I've got a Yam F150 AETX (XL-25.3") on a Ribcraft 585 which was fitted from new. I have no problems with chine walking etc.

Obviously if you can I'd stick with 20" - its going to be easier, cheaper and probably stronger than extending the transom.

However, knowing how mine sits in the water, I think a 20" F150 may sit just that little bit to low.

I would work out the weight difference between your current engine and the F150 (about 50kg?) and see how low the boat sits in the water with the extra weight at the back.
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Old 14 April 2008, 15:53   #5
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Country: UK - England
Town: Bursledon
Boat name: Mustard
Make: Ribeye 785
Length: 7m +
Engine: Yamaha 200/Merc 6
MMSI: 235068693
Join Date: Oct 2006
Posts: 618
I went for a 150 two stroke which was amost exactly the same weight as the 90 four stroke I removed. It is a longshaft, not extra long. I wouldn't want a lower transom but can't tell you how high it is. I can take some dimensions if it is a help.

The boat is pretty stable at WOT, but we are still trying different props. We haven't got full top speed yet.

I think I might worry about the weight of a 150 four stroke. We do have a wide seat in the rear of the boat, though.

Anything else I can answer?
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Old 15 April 2008, 04:46   #6
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Country: Germany
Make: RIBCRAFT 5.85
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Quote:
Originally Posted by JABS View Post
I went for a 150 two stroke which was amost exactly the same weight as the 90 four stroke I removed. It is a longshaft, not extra long. I wouldn't want a lower transom but can't tell you how high it is. I can take some dimensions if it is a help.

The boat is pretty stable at WOT, but we are still trying different props. We haven't got full top speed yet.

I think I might worry about the weight of a 150 four stroke. We do have a wide seat in the rear of the boat, though.

Anything else I can answer?
TXS @ all.

Tony, the transom is 20,47'' (52 cm) whitch is a little bit to much for L-Shaft but not enough for XL. I got one side-by-side console with 2 jockeys and a 40 gal. tank. So, not so much weight at the back of the boat. But the new Yammi 150 is a little bit more than 200kg. My problem is that i'm afraid of that the upper casing of the engine is allmost dipping into water. Right now the boat is "naked" without any engine at the back and i will not fix the old 100, 20'' just to find out how it works. On the other side i would not buy a new 150, 25'' just to find out that the 150, 20'' would do the job too.
So i'm - let's say confused right in the moment.

Really dont wanna take a look for Evenr..., Mercur... 2 or 4 Str. ' cause all the stuff (wires, gauges) are fitted to Yamaha.

So what is the better decision? 20'' and leave the transom as it is or 25'' leave the transom as it is / spend some work/money to the transom? If the boat is running with 20'' perfectly and the upper case of the engine will not touch the water i would prefer "leave it as it is".
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Old 15 April 2008, 05:29   #7
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Buying a 25" and leave the transom as it is, isn't a serious option...
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Old 15 April 2008, 06:17   #8
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Country: UK - England
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Boat name: Mustard
Make: Ribeye 785
Length: 7m +
Engine: Yamaha 200/Merc 6
MMSI: 235068693
Join Date: Oct 2006
Posts: 618
I wold not think that increasing transom height is job that could be done by anyone other than Ribcraft, who are the most helpful bunch of people you will ever meet.

I will measure my transom at the weeken.

My engine weighs 183kg. Take into account the weight of the rear seat and this suggests you will be OK.

Why not email Ribcraft and ask for advice?
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Old 15 April 2008, 13:03   #9
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Quote:
Originally Posted by JABS View Post
I will measure my transom at the weeken.
This would be perfect!

Thank you
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Old 15 April 2008, 16:07   #10
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Country: Ireland
Town: cork
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Make: HUMBER DESTROYER 5.8
Length: 5m +
Engine: 140HP sUZUKI
Join Date: Dec 2007
Posts: 262
have a suzi 140 on the back of my destroyer. There isn't much between the top of the transom and the water, how much freeboard should there be ? the engine is 186kg so wouldn't think its too heavy. The 5.8 destroyer is rated up to 205kg engine.
Haven't had anyone sitting on the back bench seat yet so will see hoe close the water is too the top of the transom then. have the anchor in the locker in the stern which adds a few kg's.
just wondering from others and even humber owners how much freeboar they have at the transom
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