Question re Avon SR4 Please

[Ribtecer]

Inspired by the SR4 threads and what some people have achieved with them - I am on the hunt for either a nice one or a good base to work up from.

Having now got something with sails I miss my old Rib and fancy dabbling back to something that smells of petrol!!!

I think I know the answer, but does a SR4 take a short or long shaft engine? Can long shaft be converted to a short easily?

Been offered a nice LS 40hp Yamaha - nice but not cheap!!!

Thanks, if anyone knows of ANY SR4's for sale please let me know.

Toby

[Newto]

On fleabay
301480972183

[Ribtecer]

Thanks for the speedy reply, I had seen that one, but thanks again.

[Firefly]

Originally Posted by Ribtecer

Inspired by the SR4 threads and what some people have achieved with them - I am on the hunt for either a nice one or a good base to work up from.

Having now got something with sails I miss my old Rib and fancy dabbling back to something that smells of petrol!!!

I think I know the answer, but does a SR4 take a short or long shaft engine? Can long shaft be converted to a short easily?

Been offered a nice LS 40hp Yamaha - nice but not cheap!!!

Thanks, if anyone knows of ANY SR4's for sale please let me know.

Toby

How much would you spend on the right boat?

[Ribtecer]

Originally Posted by Firefly

How much would you spend on the right boat?

I don't know, but I am a realist and understand that the right boat would command the right money.

Wot you got, and wot you want for it? (and where is it?)

[RIB-Teccie]

Avon 4m required a Longshaft 50hp max. Don't be tempted to cut down the transom for a short shaft engine.

[Firefly]

Originally Posted by RIB-Teccie

Avon 4m required a Longshaft 50hp max. Don't be tempted to cut down the transom for a short shaft engine.

pm me your email and I send pics etc...

[popeyethesailor]

I have a EX RNLI mariner 40 2stroke MSL Which I thought was a short shaft with an extension section inserted to increase the length of the leg but I think it is still not as long as a long shaft,
The cavatation plate is slightly above the bottom of the boat but it does not appear to cause any problems
If that helps at all

[Chris Caton]

SR4 needs a long shaft engine, as someone else has said don't nt be tempted to cut the transom to fit a shirt shaft, and just as importantly don't buy a SR4 that's had the transom cut

[Ribtecer]

Originally Posted by Chris Caton

SR4 needs a long shaft engine, as someone else has said don't nt be tempted to cut the transom to fit a shirt shaft, and just as importantly don't buy a SR4 that's had the transom cut

Thanks for the sound advice fella's

Toby

[Chris Caton]

the transom should look like this

[beamishken]

What's the big taboo with cutting down a transom to fit a short shaft? Is it something to do with the flooding hull?
Many boats this size were made short shaft & engines are often cheaper in short shaft
Quite often the centre of gravity is better with a short shaft
I've got a rib which was cloned from an sr 4 but doesn't have the flooding hull & it's absolutely fine with a 40 yam two stroke
Nothing wrong with short shaft boats & if you have a good short shaft engine there's no reason not to make the boat fit the engine
Unless I'm missing something peculiar to an sr4 of course?

[RIB-Teccie]

The Avons are a bit older in the tooth when it comes to design.

The deck is below the waterline and when moored they can swamp fairly easily. If you cut 5 inches out of the transom this becomes more likely.

As the boat sinks lower into the water, the water gets closer to the bottom crank seal and exhaust of the engine.

If it does it in a harbour tied up, spare a thought of how it would be in a breakdown in borderline weather.

The engine and boat are also more likely to swamp in a following sea or under harsh deceleration.

There is a company in the Solent that burned through a few 250 Hp four stroke Yamaha's using longshaft rather than extra longshaft engines as water was entering the bottom cylinder and damaging the engines.

[Chris Caton]

Originally Posted by beamishken

What's the big taboo with cutting down a transom to fit a short shaft? Is it something to do with the flooding hull?
Many boats this size were made short shaft & engines are often cheaper in short shaft
Quite often the centre of gravity is better with a short shaft
I've got a rib which was cloned from an sr 4 but doesn't have the flooding hull & it's absolutely fine with a 40 yam two stroke
Nothing wrong with short shaft boats & if you have a good short shaft engine there's no reason not to make the boat fit the engine
Unless I'm missing something peculiar to an sr4 of course?

Originally Posted by RIB-Teccie

The Avons are a bit older in the tooth when it comes to design.

The deck is below the waterline and when moored they can swamp fairly easily. If you cut 5 inches out of the transom this becomes more likely.

As the boat sinks lower into the water, the water gets closer to the bottom crank seal and exhaust of the engine.

If it does it in a harbour tied up, spare a thought of how it would be in a breakdown in borderline weather.

The engine and boat are also more likely to swamp in a following sea or under harsh deceleration.

There is a company in the Solent that burned through a few 250 Hp four stroke Yamaha's using longshaft rather than extra longshaft engines as water was entering the bottom cylinder and damaging the engines.

I've noticed on a few occasions just how close the SR4 is to swamping even with a full transom, I'd hate to think what might happen with one that had been cut to make a short shaft fit, the SR4 is a deep V hull to take a long shaft fir a reason so just fit one, there's not that much difference in price even on a new engine!

[beamishken]

Ah I guess that's the penalty of the flooding hull then. your purely relying on the tubes for floatation
My boat actually self bails when it's empty at rest ie if you leave the boat afloat you can leave the trunk down & rainwater just runs out
Transom height is reduced only where the engine sits & I've never been worried about taking a wave over the back & the engine is well clear of the water.
I suppose if someone wanted to run a short shaft on an sr 4 then blocking the flooding hull would be the answer

[Nos4r2]

The 5.4 is the same- I've been known to deliberately swamp mine by going astern and belt the throttle open with trunks down to wash the blood out after a messy string of mackerel. That's with the flooding hull blocked as well!

[beamishken]

Originally Posted by Nos4r2

The 5.4 is the same- I've been known to deliberately swamp mine by going astern and belt the throttle open with trunks down to wash the blood out after a messy string of mackerel. That's with the flooding hull blocked as well!

But isn't that going to happen with any boat if you misuse/abuse don't watch what your doing?
We have a 38 ft cruiser & I'm pretty sure if I slammed the throttles shut at 30+kts I'd get wet feet at the helm
I've also been on the deck of a 100m+ DSV & had to dodge waves rolling over the deck
It doesn't mean that the freeboard is too low you just have to adapt to the capabilities of the boat

[RIB-Teccie]

You don't have to misuse the boat. On a mooring some chop in an open harbour will slap off the tube and "jump" over the transom. As the craft sinks lower into the water the deck space will fill up. Fitting a bilge pump or blocking the hull will help. I liked the flooding hull when it came to stability. The thing is that short shaft engines are getting less readily available. If you want to swap or your old one dies then you have to raise the transom and its s ball ache. I've been through all of that with speedboat. I had a 40 yam SS and was planning on a 4.5m sib but a Valiant came along. After a bit of soul searching I sold the 40 and got a 55 at first and then the 50 I have now. I think cutting the transom would look a mess.

[RIB-Teccie]

As a further thought, manufacturers usually recommend 100mm clearance between the water and exhaust holes at rest. There is also the resale issue.

[matt h]

Originally Posted by Nos4r2

The 5.4 is the same- I've been known to deliberately swamp mine by going astern and belt the throttle open with trunks down to wash the blood out after a messy string of mackerel. That's with the flooding hull blocked as well!

look what happens when you catch too much Mackerel!