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Old 02 August 2018, 03:38   #1
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Country: UK - England
Town: Whitehaven
Boat name: Cerberus
Make: Destroyer 5.8
Length: 5m +
Engine: 115hp Merc 4st
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Performance - What Can I Expect?

So I've decided that, having upgraded almost everything else on my rib, its time to upgrade the hull and tubes (Can't help thinking about Trigger's broom). The typical sea state up this end of the world is choppy, which my current zodiac, although capable, isn't very comfortable in. I'm looking for a longer, deeper V hull so I can get out more and not be limited to a few trips a year. I'm very keen to keep my engine, as I've had it from new and it's only got 40 hrs on it.

I'm planning a shopping trip next week but could use some input from the forum before I go. Can anybody give me an idea of the performance I can expect from the following, with a Merc 115 4st (the current 2.1l model)?

Humber Destroyer 5.8
Destroyer 6m
Ocean Pro 5.7
Ribcraft 585
Vipermax 5.8 or 6.2

I know with the engine I have I'm not going to get stellar performance but my current boat tops out at about 37-38kts with light loads and to be honest it's fast enough. We rarely get seas calm enough to go flat out anyway.

Thanks,

Phil
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Old 02 August 2018, 03:52   #2
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Country: UK - England
Town: suffolk
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Make: Nautica/ribcraft
Length: 5m +
Engine: Yamaha 115 & 60 4str
Join Date: Jan 2015
Posts: 413
check out xs ribs ,they have prices on their site for hull only ,seem good english built ribs with a strong tornado heritage i think ,no expert but have been on a similar thought train
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Old 02 August 2018, 04:31   #3
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It's going to depend more on the weight within the boat rather than the specific model of boat - console type, seating, fuel tank, anchors etc.
25-28ish knots for a well specced boat.
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Old 02 August 2018, 04:40   #4
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Boat name: Excel Chalanger
Make: Highfield 380 Excel
Length: 4m +
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Quote:
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It's going to depend more on the weight within the boat rather than the specific model of boat - console type, seating, fuel tank, anchors etc.
25-28ish knots for a well specced boat.
I have just returned from a wee adventure down south​ and there seems to be a lot of ribcraft down there most of the 585 that I saw where 150/175 Suzuki if u are buying new most manafactorers will be more than happy for you to taste run rib just give them a call
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Old 02 August 2018, 05:16   #5
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i wouldn't put that engine on those boats.

Without knowing the max engine size of all the boats listed i would be wanting a merc 150 on them if they will take it and leave that engine on your current boat.

it isn't about top end really, just mid range and with a 6m ish boat that engine will struggle, i had the 100hp version of that engine on a 5.6.....wouldn't do it again unless a smaller boat.
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Old 02 August 2018, 07:00   #6
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Country: UK - England
Town: Whitehaven
Boat name: Cerberus
Make: Destroyer 5.8
Length: 5m +
Engine: 115hp Merc 4st
Join Date: Oct 2012
Posts: 434
As stated, I'm not looking to change the engine. The max hp for most of them is 150hp. Max for the destroyer 5.8 and vipermax 5.8 is 130hp. I'd be looking for a double console and 4 jockey seats but generally go out lightly loaded. With the 5.8's I'm not that far of max hp. Will I really only get mid 20s?

Phil

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Old 02 August 2018, 09:14   #7
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i suspect you will see 30-32 ish knots on the boats mentioned with your current engine if i had to guess (which i am obviously). i suspect you won't like the performance of a deeper V/heavier boat and marginal power so be careful.
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Old 02 August 2018, 10:06   #8
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Boat name: Hebridean Storm
Make: Coastline
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<<<Will I really only get mid 20s?>>>


Phil
No. Lightly loaded it'll do better than that. Probably between 30 & 35kn.

The issue is more the bottom end torque/hole-shot that might disappoint and that can be mitigated against to a degree by using a vented prop.. eg. Lazer, Tempest etc....
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Old 03 August 2018, 01:07   #9
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As stated, I'm not looking to change the engine. The max hp for most of them is 150hp. Max for the destroyer 5.8 and vipermax 5.8 is 130hp. I'd be looking for a double console and 4 jockey seats but generally go out lightly loaded. With the 5.8's I'm not that far of max hp. Will I really only get mid 20s?

Phil

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I was out with orwell boy and he has a Yam 115 4 stroke on a 19 foot rib so similar size to what you are looking at. Lightly loaded he gets about 32 knots if I remember correctly
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Old 03 August 2018, 10:48   #10
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Country: UK - England
Town: suffolk
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Length: 5m +
Engine: Yamaha 115 & 60 4str
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Posts: 413
check out yesterdays posted drone film on here ,mine is 115 on 19ft (5.8m) ,plenty fast enough for me ,seems plenty of power throughout range ,and i,d rather pay for a 4 cyl service than a six .
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