Reply
 
Thread Tools Search this Thread
 
Old 29 November 2007, 05:26   #1
Member
 
Country: UK - England
Town: London
Length: 3m +
Join Date: Apr 2008
Posts: 79
2 stroke or 4 stroke

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.
__________________

__________________
Lordy is offline   Reply With Quote
Old 29 November 2007, 05:54   #2
Member
 
Hightower's Avatar
 
Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,855
Quote:
Originally Posted by Lordy View Post
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.
__________________

__________________
Andy

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
Hightower is offline   Reply With Quote
Old 29 November 2007, 06:02   #3
Member
 
Country: UK - England
Town: London
Length: 4m +
Join Date: Nov 2007
Posts: 21
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!
__________________
Shed78 is offline   Reply With Quote
Old 29 November 2007, 06:59   #4
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
thirst

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.
__________________
9D280 is offline   Reply With Quote
Old 29 November 2007, 08:05   #5
Member
 
Country: UK - England
Town: London
Length: 3m +
Join Date: Apr 2008
Posts: 79
Quote:
Originally Posted by Hightower View Post
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 is offline   Reply With Quote
Old 29 November 2007, 08:27   #6
Member
 
Country: UK - England
Town: London
Length: 3m +
Join Date: Apr 2008
Posts: 79
Quote:
Originally Posted by Shed78 View Post
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 is offline   Reply With Quote
Old 29 November 2007, 08:31   #7
Member
 
Country: UK - England
Town: London
Length: 3m +
Join Date: Apr 2008
Posts: 79
Quote:
Originally Posted by 9D280 View Post
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
__________________
Lordy is offline   Reply With Quote
Old 29 November 2007, 08:37   #8
Member
 
Country: UK - England
Town: Mighty Penryn
Boat name: Little Joe.
Make: Avon Searider
Length: 4m +
Engine: Honda BF50
Join Date: Aug 2005
Posts: 8,841
Quote:
Originally Posted by Lordy View Post
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.
__________________
Mollers is offline   Reply With Quote
Old 29 November 2007, 08:43   #9
Member
 
Country: UK - England
Town: London
Length: 3m +
Join Date: Apr 2008
Posts: 79
Quote:
Originally Posted by Mollers View Post
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!!!
__________________
Lordy is offline   Reply With Quote
Old 30 November 2007, 05:23   #10
Member
 
Black's Avatar
 
Country: UK - England
Town: Bristol/Devon
Boat name: Orca
Make: Aerotec 380
Length: 3m +
Engine: Johnson 15hp
Join Date: Jul 2006
Posts: 352
Send a message via MSN to 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
__________________

__________________
Black is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 21:54.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.