Reply
 
Thread Tools Search this Thread
 
Old 31 July 2020, 09:33   #1
Member
 
Country: UK - England
Town: Fareham
Make: Avon Adventure
Length: 5m +
Engine: Merc 90
Join Date: Aug 2009
Posts: 123
How much better are 4 strokes fuel consumption

Hi, we may get another RIB in the future, our old RIB had a Merc 90 and our current boat has a Yam 70, both 2 stroke.
I like the reliability and how simple they are to look after but if we buy a newer RIB itís probably going to have a 4 stroke on it.

So my question is in the real world do the 4 strokes actually use far less fuel when comparing like for like power wise?.

Our next RIB will be around 5.5-6M ish.
__________________

__________________
martin33100 is offline   Reply With Quote
Old 31 July 2020, 10:46   #2
Member
 
Pikey Dave's Avatar
 
Country: UK - England
Town: South Yorks
Boat name: Black Pig
Make: Ribcraft
Length: 5m +
Engine: DF140a
MMSI: 235111389
Join Date: Feb 2008
Posts: 9,777
RIBase
Quote:
Originally Posted by martin33100 View Post
Hi, we may get another RIB in the future, our old RIB had a Merc 90 and our current boat has a Yam 70, both 2 stroke.

I like the reliability and how simple they are to look after but if we buy a newer RIB itís probably going to have a 4 stroke on it.



So my question is in the real world do the 4 strokes actually use far less fuel when comparing like for like power wise?.



Our next RIB will be around 5.5-6M ish.


If youíre comparing a modern efi 4 stroke to a similar HP vintage carbed 2 stroke, then itís night & day. The 2 stroke will use at least twice the fuel of the 4t probably even more. However, if youíre comparing the 4t to a modern DI 2 stroke, then in the real world, thereíd be little if anything in it.
__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4:https://www.youtube.com/watch?v=unkIVvjZc9Y
Pikey Dave is online now   Reply With Quote
Old 31 July 2020, 11:38   #3
Member
 
Country: UK - England
Town: Godalming
Boat name: Bumblebee
Make: Avon
Length: 4m +
Engine: yamaha 40hp 2stroke
Join Date: Oct 2017
Posts: 80
Yeah that's my experience too, we have a 40 4stroke and 40 2 stroke and the 2stroke is at least twice as thirsty. It is however a lot more reliable and cheaper to maintain so it depends if you use it enough to justify the fuel savings over the yearly maintenance costs
__________________
Livid is online now   Reply With Quote
Old 31 July 2020, 13:33   #4
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Yamaha 15Hp 2-stroke
Join Date: Nov 2007
Posts: 5,584
I know this experience is on the small side hp wise but...

I went from a 15hp 2-stroke to a 20hp efi 4-stroke a few years ago (and back again but that's another story) and managed about 50% extra distance at slightly greater speeds. For me the greatest benefit was the greater range for a given tank size.
__________________
Fenlander is offline   Reply With Quote
Old 31 July 2020, 15:46   #5
Member
 
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Excel 435
Length: 4m +
Engine: Suzuki Outboard/25/4
Join Date: Oct 2011
Posts: 6,128
RIBase
The only offering I have is on our long trips with gurnard he had a 25 two stroke on a 420 sib I had a 25 four stroke on a 3.65 sib I was 15% better off but if you equal the boats and weight I think more the 10% worse for the two stroke.
__________________
jeffstevens763@g is offline   Reply With Quote
Old 01 August 2020, 00:09   #6
Member
 
Country: UK - England
Town: Nottinghamshire
Make: Mercury Ocean Runner
Length: 4m +
Engine: Mercury F40 EFI
Join Date: Jul 2016
Posts: 293
Quote:
Originally Posted by martin33100 View Post
So my question is in the real world do the 4 strokes actually use far less fuel when comparing like for like power wise?.
Evinrude etec direct fuel injection two strokes are at least as good if not better than a four stroke. Caloundra Marine videos on YouTube usually include the fuel consumption in their comparison reviews. If buying a new outboard, would be on my shortlist.
https://youtu.be/tZvIw83uZgY
__________________
Limecc is offline   Reply With Quote
Old 01 August 2020, 02:51   #7
Member
 
Country: UK - Scotland
Make: Destroyer 5.5/Ring18
Length: 3m +
Engine: Yam 90HP/Yam200HP
Join Date: Jul 2009
Posts: 718
Quote:
Originally Posted by Limecc View Post
Evinrude etec direct fuel injection two strokes are at least as good if not better than a four stroke. Caloundra Marine videos on YouTube usually include the fuel consumption in their comparison reviews. If buying a new outboard, would be on my shortlist.


I thought Evinrude stopped making outboards
__________________
69cmw is online now   Reply With Quote
Old 01 August 2020, 02:59   #8
Member
 
Country: UK - England
Town: Godalming
Boat name: Bumblebee
Make: Avon
Length: 4m +
Engine: yamaha 40hp 2stroke
Join Date: Oct 2017
Posts: 80
Yeah as of a few weeks ago they have so I wouldn't recommend buying one unless you're willing to roll the dice
__________________
Livid is online now   Reply With Quote
Old 01 August 2020, 05:33   #9
Member
 
Country: UK - England
Town: Fareham
Make: Avon Adventure
Length: 5m +
Engine: Merc 90
Join Date: Aug 2009
Posts: 123
Thanks the replyís guys, if we use the RIB like our last one we may do a lot of towing ie water sports so I guess a DI 2 stroke may give us the best of economy and power?.
However if the right RIB comes up for sale with a 4 stroke on it I am not that bothered about the servicing costs as my labour is free.
I am one of the maintenance techs at Southampton Container terminals and I did my apprenticeship building Diesel engines so I donít mind having a go at most things.
__________________
martin33100 is offline   Reply With Quote
Old 01 August 2020, 05:55   #10
Member
 
Pikey Dave's Avatar
 
Country: UK - England
Town: South Yorks
Boat name: Black Pig
Make: Ribcraft
Length: 5m +
Engine: DF140a
MMSI: 235111389
Join Date: Feb 2008
Posts: 9,777
RIBase
Quote:
Originally Posted by martin33100 View Post
Thanks the replyís guys, if we use the RIB like our last one we may do a lot of towing ie water sports so I guess a DI 2 stroke may give us the best of economy and power?.

However if the right RIB comes up for sale with a 4 stroke on it I am not that bothered about the servicing costs as my labour is free.

I am one of the maintenance techs at Southampton Container terminals and I did my apprenticeship building Diesel engines so I donít mind having a go at most things.


Having owned boats with both DI 2 strokes & 4 strokes, my experience is that thereís much more ďgruntĒ with the 2 strokes & neglible difference in fuel economy. The 4 stroke cost of ownership is much higher, due to the (imo) excessive servicing requirements.
__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4:https://www.youtube.com/watch?v=unkIVvjZc9Y
Pikey Dave is online now   Reply With Quote
Old 01 August 2020, 12:06   #11
Member
 
Maximus's Avatar
 
Country: UK - England
Town: Wild West
Boat name: No Boat
Make: No Boat
Length: under 3m
Join Date: Jan 2008
Posts: 4,878
Send a message via AIM to Maximus
I've owned many 2strokes over the years.....but things move on and I do prefer 4strokes overall ...I find them much more economical... I like the quiet running....no oil to worry about...and if you've ever followed 2strokes at Sea for a period just hope you've enough Gee Gees to overtake..( especially a twin set up)
The Trick with any engine choice for a RIB ...is to match the engine Size (Power) to the Hull AND loading expected Then prop it properly!... to get the performance your after
As for 2strokes v Four I can only speak from my experience

I've trialed/raced 250 HO g2 Tws strokes (on a LIGHTER Newer RIB!) ...against my own set up 6.8 RC with 250 Df in hole shot tests over a few hundred yards...
Result NOTHING in it!!!...not even 1/2 a Boat length.
Now that's a real world test!
"Hole shot" for me is paramount....but topping out at 48knots in a Heavy layup Ribcraft 6.8 isn't too shabby...I could possibly improve on top end....but Grunt and Holeshot punch may suffer.
Try some different combinations...but ultimately get the engine Size/choice/set up/prop/..RIGHT and you'll get the best out of you're chosen package regardless
__________________
A clever Man learns by his mistakes..
A Wise Man learns by other people's!

The Road to HELL ..is Paved with "Good inventions!"
Maximus is offline   Reply With Quote
Old 02 August 2020, 07:21   #12
Member
 
Country: UK - England
Town: Fareham
Make: Avon Adventure
Length: 5m +
Engine: Merc 90
Join Date: Aug 2009
Posts: 123
Thanks for the advice guys, our old RIB was an Avon Adventure D560 and it went well with a Merc 90 2 stroke.
Ideally our next boat will be similar size or up to 6M, however prices are very very high at the moment.
__________________
martin33100 is offline   Reply With Quote
Old 02 August 2020, 07:50   #13
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 1,984
RIBase
I had an Avon 5.4m Searider with a carb 2 stroke Mariner 90.
Changed to a 6.5m Scorpion with 150hp Optimax - a boat probably 75% heavier and the fuel consumption was about the same at a litre a mile.
(better than a litre a mile at below 25knots).
Very happy with my Optimax.

I considered all engines when our Opti got to 900hrs and 15 years old.
Sea trialled a 150hp Selva 4 stroke which felt very weak in comparison with the Opti.
Liked the look of an E-tec.
However, bought another Opti when a good deal came up on a low hours one.

If money were no object I'd probably consider one of the new mercury 4 strokes 150hp or the V6 175hp simply because we do more low speed coaching now and the Opti is a bit loud!

Now that E-Tecs arent being made I'd probably avoid those.
Tohatsu TLDI is the same tech as Optimax and worth a look if the price is right.
__________________

__________________
Searider 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




All times are GMT -5. The time now is 04:21.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.