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-   -   overpowered searider (https://www.rib.net/forum/f8/overpowered-searider-8224.html)

dodl 17 December 2004 14:32

overpowered searider

Today i read a very interesting post from Rogue wave, about over engined seariders. He wrote he saw some of them with struts from the transom to the deck.

Now i don't really want to overpower my 470, but i really like the idea of 2x50HP on the transom. That's not much overpowered, but pretty heavy. Is the deck really that solid, so it's enough to put struts to the deck? I always thought they should go down to the hull/stringers. Although i could not find stringers, when looking into the hull through the big hole at the stern.

On the other side, maybe the deck is really that solid, since the force created by an expanding self righting bag should also be pretty heavy...

Rogue wave, would you think it is possible to mount 2x50HP (about 320-360lbs), by simply adding some struts from transom to the deck?

many thanks

PS: I know the discussion about pro's and con's with twin engine setups, but i like them. :D

Biggles 17 December 2004 14:40

Hi Dodl

For your information mine has two struts either side of the transom going from the transom on the inside and fixed to the floor. It looks like these were fitted when the boat was made. Also at some stage a piece of heavy duty stainless steel has bee added to the transom. I don't know if this was part of the original build. Should add some strength, unless its hiding something.

However in your case as you already know the condition of your transom you could put the plate over it. I'm no engineer but I assume it helps to spread all the forces.

If you want I can get some pictures for you.

Regards Biggles.

dodl 17 December 2004 14:45

Hello biggles,

Yes i also have those 2 struts. But a picture of this stainless steel piece would be very nice :D

By the way, this week on Tuesday i got mail. Many Thanks! :cool:


PS: How is your carb rebuild going?

Biggles 17 December 2004 14:53

Martin I will get the picture tomorrow.

The carb rebuild went well. They look like new, I learnt a lot and best of all they work. They fired up straight away even though the cylinders were full of 2 stroke for the winter.

Had a few minor problems along the way but had a spare set to refer to when I got stuck.

We must find somewhere reasonably priced to buy spares for the engine.

The jokers in the UK must all be called Arthur Daley...

Mastertech in Hawai sounded promosing but he took too long to get back to me because he'd been hit by a Hurricane.

Regards Nick.

ribraff 17 December 2004 14:55

Transom support
I think the Sea-rider would be more than capable of handling a couple of 50's, it might be an idea to remove the stainless knees on your boat and have some made, if you know anyone who is capable of GRP work you could have them custom build them from foam which is then encapsuled in fibre glass, this will spread the loading across the deck better than the stainless bars which avon use. This is of course all IMHO

Searider 17 December 2004 15:28

SS Struts / tie bars
The majority of Seariders should have SS tie bars from the transom to the deck as built. There are some exceptions to this however, my 4m had a moulded gelcoat finish inner moulding and this incorporated GRP knees between the transom and floor.

Kernow Buoy 17 December 2004 15:40

overpowered Searider
Who has?
Don't worry Duncan we'll get them for you. Well when I say we.....

Rogue Wave 17 December 2004 15:53

David Manning did a very good job on his sea rider there are pics on the forum somewher I'll have a search for them. I have a searider hull that used to have a 115 yammie and has a superb steel strengthening plate fitted. I'll take a photo of the thing and post it Probably take me about a month to get it together I exzpect.

I would bolt the strengtheners through the deck or glass in bigfootplates when doing the work.

Pete7 17 December 2004 16:04

1 Attachment(s)
Martin, I think you are right to be worried about the weight of 2 x 50hp engines on the stern of a 4.7m rib. If you do want twin engines how about something smaller. This is an Osprey Sparrowhawk 5.2m that was built in 91 to compete in the round Scotland Rib Race. The Engines are 2 x 30hp Suzukis which Osprey managed to get up to 40 mph out of it. Would you not choose two smaller engines and have a better balanced rib.

Dave Manning highlighted the problems of balance in this recent thread too.


The 5.4m Avon RW was talking about had substantial Ali plates that covered the inside transom including the engine mounting bolts and a similar sized plate on the deck joined with ali webs. This was fixed with screws and epoxy resin. Curiously I think this boat is destined for my orchard this weekend to await the spring and lots of TLC. It did hae a Yam 115 but it must have been quite a handfull on full throttle :eek:


CJL 17 December 2004 17:32

I'd be very very careful.

S/S only moves the forces around the boat.

If you beef up the transom great, it'll break somewhere else instead.

Boats have a rated transom for a reason.

Anyway have you thought about how the weight will affect the ride, afloat and on a trailer?


dodl 17 December 2004 18:11

Wow, so many replies...
Where to start?

Of course i am very careful, and indeed i thought i'll pass on it. Then i read the Post from Rogue wave. Well, the boat is rated up to 140kg on the transom. 2 50HP Mercs (which i have) are about 160-180kg. Right now i have 60 Litres fuel and the battery at the stern, which will move up front, since i build a new console, where the tanks can be installed.

I would not use SS struts, but want to laminate some Transom knees. My only concern was /is the stability of the deck. Knees would distribute the stress over a lenght of 25-30cm to the deck. 4, maybe 6 knees would be possible. They shall be of 20mm Plywood, mounted to transom and deck with 2" epoxy/microfibre fillet joints, glassed with two layers of biaxial tape. The boat is rated for 70HP. In fact 2x50 would be about the same as a single 75HP engine. I am sure the knees would be strong enough, but i do not know about the deck and the hull itself. Of course the transom itself would be strengthened with a ss plate an fillet joints all around.

Today i saw pics of a Bombard Explorer which runs with 200HP instead of 65. Compared to this, i am very conservative :D


Nick - great job with your carbs. And thanks for the offer of the pic's...

Biggles 18 December 2004 09:17


I have just E Mailed you the pictures of the transom.

Hope it helps.


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