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Old 07 December 2011, 13:09   #1
hamster's Avatar
Country: UK - England
Length: 4m +
Join Date: Aug 2006
Posts: 196
Searider flooding hull


What do people use to block off their flooding hulls?

I want to be able to block off the flooding hulls on two of my 4m seariders so that when they are used as safetyboats on the sea they plane easier and use less fuel.

They will only be used on the sea occasionally though and I want them to flood when back on the lake here as they spend a lot more time at displacment speed so I want them lower in the water and more stable.

I'm therefore looking for a tempory thing that I can use to block the rear hole when I choose to. I can fit some screw bung fittings to the front holes so these can be blocked as well when necesarry.

I've seen various things on here that people use in the past but can't easily find them from doing a search.


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Old 07 December 2011, 14:39   #2
Country: Germany
Town: StPetersburg Russia
Boat name: Ocean Devil
Make: Scorpion 8.6m
Length: 8m +
Engine: Yanmar 315hp
MMSI: 211579640
Join Date: Aug 2009
Posts: 636
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Hi ,
I found a very nice SS cover in one of the shops in Germany - have a look :

Pinnendurchfhrung 99,90 € - SVB

It fits perfectly well . All you need to open / close it is a 3/4" drive ratchet or similar .

Regards - Jürgen
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Old 07 December 2011, 15:13   #3
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 2,061
I don't think that you'll save any (much) fuel by blocking off the flooding hull.
In a well set up boat i'm not convinced it helps you plane much earlier.

My 4m has the hull open and "only" 30hp. It has the standard Avon Rescue console and is propped to give about 26knots flat out (I haven't checked the rpm).

I never have any problem getting on the plane and the water drains out in an instant. You can even get it to drain out gently at about 6 ot 7 knots.

My previous 4m might have benefited from having the hull blocked. It had the back to back seating and a 50hp all manual 2 stroke. Would do 37knots 2 up but took a while to get on the plane. With 4 up if there was any chop it sometimes wouldn't plane, or would take forever.

Don't forget that the purpose of the flooding hull is to give the boat stability at rest when there are some waves - ie when you're sat in it as a rescue boat, on the sea!
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Old 07 December 2011, 15:34   #4
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,667
Wot searider said......

...but mine had a 25Hp!
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Old 07 December 2011, 16:28   #5
hamster's Avatar
Country: UK - England
Length: 4m +
Join Date: Aug 2006
Posts: 196
Thanks guys

Searider - What prop are you running on your 30hp?
Ours 'only' have yam 30's on the back which is plenty for most jobs, especially with lots of different people driving the boats.
I've just been out for a spin in both boats though and found they were only reaching 4500 and 5000rpm with 11 x 13" and 11 x 12" props respectively. The 12" props pull a lot better and gives better high speed (25kts vs 22kts on flat water with 2 people onboard) however I'd like a bit more grunt when the boat has a bit of water in it as well as a couple of wet kids on board and kit etc. I've just ordered a couple of 11 x 11" props to try which will hopefully help get the revs up higher and get the boat planning easier.
I think I'll stick with the 11 x 12" prop when using the boats on the lake and use thew 11" on the sea as they get used by lots of different people on safety boat duty who like to have a bit of a spin when my backs turned so I'm hoping that by over proping the boat it'll help keep their speed down as well as my fuel bill if the engines can't rev as much it'll hopefully help them last a bit longer.
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Old 07 December 2011, 17:14   #6
Nick Hearne's Avatar
Country: UK - England
Town: Bucks
Boat name: Blue & Ding Dong
Make: Ribeye,SR4 & Bombard
Length: 6m +
Engine: 115,50 & 15Hp Yams
Join Date: Feb 2004
Posts: 3,252
I blocked mine off to get on the plane faster to get me waterskiing!
But it made little difference & ended repropping, I think it would be better left open as it would have more weight up front to keep the bow down at take off!
The best advantage being blocked is you can keep to a speed with ease as when open you have to keep playing around with the throttle as she starts to take off as the water drains out! At rest she feels very light with out the extra weight of the water in the hull which I do not like
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