2 stroke or 4 stroke

[Lordy]

I'm looking to buy a SIB, probably Zodiac Futura, around 4m in size.

I would prefer to keep as much room available as possible in the boat, so am opting for tiller steering. Maximum engine size I would go for, therefore, would be 25 or 30hp, as I have read that anything bigger becomes difficult to control manually.

I'm going for as large an engine as possible as I'd like to pull inflatables etc. And we're a family of 5.

My dilemma is whether to go 2 stroke or 4 stroke, if I can find a second-hand 2 stroke.

While on one hand 2 strokes appear to be alot lighter, on the other they are obviously alot noisier. I've also read somewhere that they are also alot thirstier.

Has anyone had any experience of the 2 options in this power range? And would anyone know what you would typically get per litre from a 2 stroke compared to a 4 stroke? Also, is there any difference in control - is a 4 stroke harder to control than a 2 stroke?

On the subject of control, if I'm going to tiller steer, is there anything you can add to the engine to make it easier to control. (Apart from a jockey console!!)

Many thanks.

[Hightower]

Originally Posted by Lordy

I'm looking to buy a SIB, probably Zodiac Futura, around 4m in size.


I'm going for as large an engine


While on one hand 2 strokes appear to be alot lighter

on the other they are obviously alot noisier.

I've also read somewhere that they are also alot thirstier.


On the subject of control, if I'm going to tiller steer, is there anything you can add to the engine to make it easier to control.

I think you've answered you own question!

For that sized boat you want to keep things as light as possible and really gives you one option for the power output you want.

Yes 2 strokes can be thirsty unless you can get an injected model. Depends how much you use it and how you use it.

As for noise.......Can you hear any engine noise above the wind noise when blatting along?

I think there's a damper unit that helps control tiller outboards, the Zapcat boys can help you there.

[Shed78]

Hi Simon,

We meet again!!

Some dealers still have 2 strokes available, I spoke to the one on Shepperton Lock and he had some good deals on Mariner 2-strokes.

As you want it portable I think a 30hp 4 stroke is going to be very heavy. The Mercury 30hp 2 stroke is 49kg, I am a big bugger and can lift it ok - but actually walking with it is difficult. I have just fabricated a lightweight engine stand on wheels (like sack trucks) to make life easier.

The Mercury 30hp 4 stroke is 80kg... and i wouldn't want to be man-handling that sort of weight around... let alone trying to install it on the back of the boat whilst it's on the water.

Cheers,

Steve

P.S - I should be picking up the trailer at the weekend...so I'll be ready to go with my setup - hardly the time of year however!

[9D280]

I guess if youre towing toys you'll be at or around WOT most of the time, in
which case your fuel consumption won't be too different 'tween 2 and 4 strokes. Bottom line is petrol in a cylinder is quite fussy when it comes to going bang - for a given HP, most engines will be around the same CC, so at a nice 14(ish):1 mix, you'll be drinking the approx the same amount of petrol no matter how many strokes it uses. It's long term use at low - mid RPM where 4- stroke / EFI comes into it's own.

I guess if youre going for a SIB portability is going to be important - Also remember a lot of engines use the same block etc for a couple of HP variants, so make A's 30 may be well heavier than make B's if make A's 30 is a restricted 40 and Make B's also doubles as the 25.... Speaking from experience I wouldn't ideally like to lug more than a 25 up a beach.

[Lordy]

Originally Posted by Hightower

I think you've answered you own question!

For that sized boat you want to keep things as light as possible and really gives you one option for the power output you want.

Yes 2 strokes can be thirsty unless you can get an injected model. Depends how much you use it and how you use it.

As for noise.......Can you hear any engine noise above the wind noise when blatting along?

I think there's a damper unit that helps control tiller outboards, the Zapcat boys can help you there.

Thanks Hightower

I'll go 2 stroke then!!

Simon

[Lordy]

Originally Posted by Shed78

Hi Simon,

We meet again!!

Some dealers still have 2 strokes available, I spoke to the one on Shepperton Lock and he had some good deals on Mariner 2-strokes.

As you want it portable I think a 30hp 4 stroke is going to be very heavy. The Mercury 30hp 2 stroke is 49kg, I am a big bugger and can lift it ok - but actually walking with it is difficult. I have just fabricated a lightweight engine stand on wheels (like sack trucks) to make life easier.

The Mercury 30hp 4 stroke is 80kg... and i wouldn't want to be man-handling that sort of weight around... let alone trying to install it on the back of the boat whilst it's on the water.

Cheers,

Steve

P.S - I should be picking up the trailer at the weekend...so I'll be ready to go with my setup - hardly the time of year however!

Hello again Steve - good to hear from you!

As I haven't yet owned a RIB/SIB, I hadn't considered having to install an engine while the boat is in the water. Very good point!!

I'm a big bugger too, but regrettably only around the waist, so 80kg is going to be way too much for me. Even 50 sounds a bit of an ask!

I'm going to try and go to the boat show this week-end, so I'll try lifting a few, but would be great to see a photo of this engine stand you've built. (I expect being an engineer helps!) A pic of your trailer would be interesting too.

Look forward to hearing how it all goes with the new set up. When are you planning to launch?

Simon

[Lordy]

Originally Posted by 9D280

I guess if youre towing toys you'll be at or around WOT most of the time, in
which case your fuel consumption won't be too different 'tween 2 and 4 strokes. Bottom line is petrol in a cylinder is quite fussy when it comes to going bang - for a given HP, most engines will be around the same CC, so at a nice 14(ish):1 mix, you'll be drinking the approx the same amount of petrol no matter how many strokes it uses. It's long term use at low - mid RPM where 4- stroke / EFI comes into it's own.

I guess if youre going for a SIB portability is going to be important - Also remember a lot of engines use the same block etc for a couple of HP variants, so make A's 30 may be well heavier than make B's if make A's 30 is a restricted 40 and Make B's also doubles as the 25.... Speaking from experience I wouldn't ideally like to lug more than a 25 up a beach.

Thanks 9D280,

But what's WOT?

From responses so far, seems like a 2 stroke is a bit of a 'no-brainer'!

Cheers,

Simon

[Mollers]

Originally Posted by Lordy

Thanks 9D280,

But what's WOT?

From responses so far, seems like a 2 stroke is a bit of a 'no-brainer'!

Cheers,

Simon

WOT? Eh? Wide Open Throttle.

If you're a 'big bugger' maybe you could not bother with the boat and shove an outboard down the back of your Speedos.

Yeah, definitely a 2st at that size, lighter and more zip.

[Lordy]

Originally Posted by Mollers

WOT? Eh? Wide Open Throttle.

If you're a 'big bugger' maybe you could not bother with the boat and shove an outboard down the back of your Speedos.

Yeah, definitely a 2st at that size, lighter and more zip.

Thanks for explanation...but big buggers wouldn't wear Speedos, not if they've got any sense!!!

[Black]

Hi Simon,

I've got a 20hp Yamaha on the back of my 380 Quicksilver and to be honest I wouldn't want to lift any more than that. If I am taking it down the beach I get someone else to help me carry it.

I am pretty sure that it is the same size block as the 25, so on a Yamaha you could go upto 25hp. It is 49Kgs with the fluids. Have to agree with the other comment about the 80Kgs engine, that for me would be physically impossible to lift in the form off an engine.

You are right to go and try and lift a few at the boat show - bear in mind that they will all be bolted onto stands. Have a chat to the Barrus guys - they are who I got my 20hp Yamaha 2 stroke from recently.

Black

[jyasaki]

Originally Posted by Lordy

Thanks for explanation...but big buggers wouldn't wear Speedos, not if they've got any sense!!!

Unfortunately, big buggers don't always follow your sentiments.

jky

[RibinSpain]

interesting thread here as I have a 4 stroke yamaha 80 & use it mainly mid range, v low fuel consumption.

Anyway, I have a 2 stroke Stihl strimmer & had its first service yesterday after 4 years & c 400 hrs. It took 5 mins & cost 10e!!! Starts second time all the time & used WOT (sorry neighbours I know its loud) for 1 week a year.

Cheers all

[ian parkes]

with a family of 5 I reckon a futura would be pretty sluggish with a 25hp.

You would need the mk3 futura to get enough space and that is a bit big and heavy to inflate every time you use it so you will end up with a trailer anyway so a bigger motor wouldn't be a problem .

My25 yam on a futura used the same amount of fuel as my df70 suzuki on a 4.9 rib for half the performance . It was much more hassle to launch and recover due to the type and height of trailer it needed . For the cost of a futura trailer and motor new you could get a decent rib or hardboat on a trailer .

[prairie tuber]

Originally Posted by ian parkes

with a family of 5 I reckon a futura would be pretty sluggish with a 25hp.

You would need the mk3 futura to get enough space and that is a bit big and heavy to inflate every time you use it so you will end up with a trailer anyway so a bigger motor wouldn't be a problem .

My25 yam on a futura used the same amount of fuel as my df70 suzuki on a 4.9 rib for half the performance . It was much more hassle to launch and recover due to the type and height of trailer it needed . For the cost of a futura trailer and motor new you could get a decent rib or hardboat on a trailer .

The 5 of you could fit into a a Mark II Futura if you are not bringing along any gear, but it will be pretty slow if being pushed by a 25 hp outboard.

[Lordy]

Originally Posted by prairie tuber

The 5 of you could fit into a a Mark II Futura if you are not bringing along any gear, but it will be pretty slow if being pushed by a 25 hp outboard.

Thanks again Prairie Tuber

More dilemmas!

I've seen a fantastic deal on a Futura MK2 with a console and 50hp, but with console and seats it looks a bit neat for 5. Would also need a trailer, and I've decided I'd prefer not to go that route.

But then, if I stick to tiller steer, max I've been recommended is 30hp, which is going to be sluggish with family of 5.

Back to the drawing board!!

[Lordy]

Originally Posted by ian parkes

with a family of 5 I reckon a futura would be pretty sluggish with a 25hp.

You would need the mk3 futura to get enough space and that is a bit big and heavy to inflate every time you use it so you will end up with a trailer anyway so a bigger motor wouldn't be a problem .

My25 yam on a futura used the same amount of fuel as my df70 suzuki on a 4.9 rib for half the performance . It was much more hassle to launch and recover due to the type and height of trailer it needed . For the cost of a futura trailer and motor new you could get a decent rib or hardboat on a trailer .

Thanks Ian

Prairie Tuber says the same (see my response) so now I'm back to the drawing board.

I had seen a 2003 model MK3 Futura, which I was very tempted by, but thanks for the warning if they are that heavy. Apart from lifting/packing I suppose I'd need an even bigger engine, which would probably rule out tiller steering.

It's a shame there isn't somewhere where you could actually go and try the various options out!!

[ian parkes]

Originally Posted by Lordy

Thanks Ian

Prairie Tuber says the same (see my response) so now I'm back to the drawing board.

I had seen a 2003 model MK3 Futura, which I was very tempted by, but thanks for the warning if they are that heavy. Apart from lifting/packing I suppose I'd need an even bigger engine, which would probably rule out tiller steering.

It's a shame there isn't somewhere where you could actually go and try the various options out!!

My futura was on a proper break back sib trailer . Compared to a normal roller or bunk trailer it was a pain for launching . The trailer supports under the tubes hence the boat sits quite high so it won't just float off . Also the motor needs seperate support so its wieght doesn't damage the tubes so you spend extra time sorting that out . However 5 of you would probably be able to lift it on and off the water by hand unless the kids are small .
At half throttle it did 18mph and at wot it did just over 20 . You could feel the resistance of the floppy hull building up , I wanted a bigger motor but came to the conclusion it would probably just push water backwards faster for a small gain in speed .
I do like tiller steering and would love to try something like my little valiant with a 50 hp tiller steer , maybe thats your route .
The bigest 4m honda with an alloy floor 30 would be my choice for a sib as the hull is much more rigid and its half the price of a futura .

[Mollers]

Originally Posted by ian parkes

My futura was on a proper break back sib trailer . Compared to a normal roller or bunk trailer it was a pain for launching . The trailer supports under the tubes hence the boat sits quite high so it won't just float off . Also the motor needs seperate support so its wieght doesn't damage the tubes so you spend extra time sorting that out . However 5 of you would probably be able to lift it on and off the water by hand unless the kids are small .
At half throttle it did 18mph and at wot it did just over 20 . You could feel the resistance of the floppy hull building up , I wanted a bigger motor but came to the conclusion it would probably just push water backwards faster for a small gain in speed .
I do like tiller steering and would love to try something like my little valiant with a 50 hp tiller steer , maybe thats your route .
The bigest 4m honda with an alloy floor 30 would be my choice for a sib as the hull is much more rigid and its half the price of a futura .

.....and Parksey is partial to a pair of Speedos.

[Ian M]

As a dive club we used to run a couple of ex RNLI 40hp Mariners on tiller steering, on a couple of SIBS, with no problems, even the slightly built girls in the club used to drive them! Some of us even used to sling the outboards over our shoulders and carry them up the beach (wouldn't like to try it these days though!).

[prairie tuber]

There shouldn't be any issues operating a 40 or 50 hp tiller. Tiller handles tend to become longer with increased hp to provide the operator with more mechanical advantage. Tiller controlled outboards of up to 200 hp are quite common in North America.

The other concern I'd have about the Zodiac Futura is that unless it is a military one, it will be constructed of PVC rather than hypalon, which will give you about a 1/3 of the life expectancy. The FC-470 is Zodiac's military version of a Mark III futura (4.7m) which is made of 1880 dtx hypalon, weighs 330 lbs (150 kg) and costs about twice that of it's PVC recreational counterpart.