Sink or not sink?

[javelin]

We've converted our 5.6 searider from a twinn 55 to a single 55hp.
The question is whether to block the sinking holes or to allow it to take on water.

It will be used as a safety boat, moving sailing marks about etc on the sea so much of the time it will be just pottering around at 4 or 5 knots, essentially waiting for trouble.

There are those who say we'd use a lot less fuel if we blocked off the holes.
Whilst others say we'd be better off with a more stable platform.

Your thoughts?

[HUMBER P4VWL]

We had a 5.4 searider for over 10 years. We sunk for 2 and floated for the rest. Have to recommend blocking it up. Less fuel especially if pottering around. Much quicker to get up on the plane, useful for getting to rescues. Also still just sits on the tubes so perfectly stable. Also, the transom is so low to the waterline on seariders, any extra height will stop waves sloshing over the back. The only advantage of sinking is if you were hauling massive weights in and out of the boat at stand still, is diving, it sits even more on the tubes, then cruising back to shore it empiries out. For you pottering round, on and off plane, seal it up!

[JSP]

Originally Posted by javelin

We've converted our 5.6 searider from a twinn 55 to a single 55hp.
The question is whether to block the sinking holes or to allow it to take on water.

It will be used as a safety boat, moving sailing marks about etc on the sea so much of the time it will be just pottering around at 4 or 5 knots, essentially waiting for trouble.

There are those who say we'd use a lot less fuel if we blocked off the holes.
Whilst others say we'd be better off with a more stable platform.

Your thoughts?

Humber said it all really. Do a search on searider flooding hull on here and you will find loads of threads on the subject.

[mdt]

as an aside I am planning to not flood the hull on my project 5.4. and was thinking of seeing if you can get XL shaft 90hp and then I could build up the transom by 5” to help prevent shipping water when astern ? I spent the weekend in a 5.4 with a flooding hull and a 125hp hung on the back. Water over the transom if you even think of going astern ?

but back to the question. I would block it off.

[JSP]

Originally Posted by mdt

as an aside I am planning to not flood the hull on my project 5.4. and was thinking of seeing if you can get XL shaft 90hp and then I could build up the transom by 5” to help prevent shipping water when astern ? I spent the weekend in a 5.4 with a flooding hull and a 125hp hung on the back. Water over the transom if you even think of going astern ?

but back to the question. I would block it off.

Yeah the waterline is very close to the transom, specially with my yam but with a 125

[mdt]

it was a 2smoke don't stress. i have to say i did not notice the flooding hull holding it back much.

[javelin]

OK sealed up it is then.

Took her out for a first test tonight.
She gets on the plane but she takes her time and I guess this could be the prop as the current single engine was, until our a conversion, one of a pair.

So, and I guess you can tell there's a noob about,
5.6 searider.
Used on the sea.
Single 55hp Evin "commercial" two stroke,

what prop should I be using?
Where do I get one?
I hear it should be alloy so we dont strip the gearbox when the driver gets a line wrapped up.

Cheers

[JSP]

Originally Posted by javelin

OK sealed up it is then.

Took her out for a first test tonight.
She gets on the plane but she takes her time and I guess this could be the prop as the current single engine was, until our a conversion, one of a pair.

So, and I guess you can tell there's a noob about,
5.6 searider.
Used on the sea.
Single 55hp Evin "commercial" two stroke,

what prop should I be using?
Where do I get one?
I hear it should be alloy so we dont strip the gearbox when the driver gets a line wrapped up.

Cheers

If I were in your boat (pun) I'd sell both 55's and opt for some more power.

[JSP]

Originally Posted by mdt

it was a 2smoke don't stress. i have to say i did not notice the flooding hull holding it back much.

Sounds good

[HUMBER P4VWL]

i'd agree with jsp, more power needed. we had an old 75 carbed engine, just enough. Then had an opti 90, very quick indeed. Probably slow onto the plane due to power?!!

[Nos4r2]

Originally Posted by javelin

OK sealed up it is then.

Took her out for a first test tonight.
She gets on the plane but she takes her time and I guess this could be the prop as the current single engine was, until our a conversion, one of a pair.

So, and I guess you can tell there's a noob about,
5.6 searider.
Used on the sea.
Single 55hp Evin "commercial" two stroke,

what prop should I be using?
Where do I get one?
I hear it should be alloy so we dont strip the gearbox when the driver gets a line wrapped up.

Cheers

What prop is on there now?

[mdt]

Untimely you would be looking for (said in a Clarkson style) more power.

However I would block up the holes first and see how it goes. You might be surprised. I had a 5.4 with a old yam 60 on it and it was ok with 2 on board, with 3 it was still managing to plain ok and it had a flooding hull. I have read that there is about 400kg (it will go out the back quite quick but it is still there) of water in a 5.4 hull at rest so I would guess on a low powered set up this could make a huge difference.

And remember blocking the holes up is very cheap and easy to reverse. If you think about how you are to go about it.

[javelin]

The issue with more power is with the mixed ability of the people who will be opperating the rib.
Which is afterall why we converted from twinn 55s to the single.

Yes a 70 fourstroke would be ideal but we're a small sailing club and finance like that is not easy to come by.

Blocked up the holes today and fitted a bilge pump.
Fitted the vhf and checked the regulator and the charging system.
Messed around with the cable adjustment for ages trying to get neutral, reverse/forward in the correct place and think I got there in the end.
Went for a blast down the coast and all seemed fine.
On the sea she felt far better than she felt on the high speed section of river.
Hand held GPS says 24knts compared to the twin setup which we saw 36knts.
So in terms of speed and the sort of use she'll have I think performance is about right.

That said, I think that the engine might need flattening out a little as she tends to go nose high and at around 4-6knts she throws out a big wash.
I think that she'd benefit from a finer prop especially when we have to tow dingies in and out of the harbour.
However like a fool I forgot to check what prop we have - I'll do that tomorrow.

Thanks for all the help thus far.