It just doesn't seem right?

[Clipper]

had a big trip in the sib yesterday, 48 km or 29 mile. what doesn't seem to add up is the fuel consumption? i used approximately 4-5 litres. hard to tell because the tanks still full

launch in perfect conditions in the morning, 3-4 knots, 0.6m swell and travelled to some offshore islands. wind picked up during the day to 9-12 knots. there were only two people in my sib and a bit of gear. though my sib is small, 3.4m with an 18hp, I was planning to go through the entire 25lt tank with crossing open ocean.

the other sib that made the trip with me used a lot more fuel, it was a bit bigger 3.8m with 25hp and 3 people on board, they used 18 litres.

it just doesn't seem right?? so little fuel for such a big trip??

[chewy]

Two or four stroke?

[Clipper]

this is a map of the trip we did, the place we launched from is wilsons prom which is the southern most point of the australian mainland, a very dangerous place with winds and currents, but offers some fantastic diving.

chewy; both out board were 2 stroke.

[mmgarrett]

I am surprised every time I take out my sib as well. It seems like I am spending more money on fuel stabilizer than I am the fuel. I have often wondered how I am getting such great fuel economy. If you think about how little effort it takes for a balloon to move along the water then it will make sense why you are getting such great millage. I just wish I had the same issue with my car!
-Matt

[Clipper]

matt, i hear what you're saying in regards to the lightweight nature of SIB's not demanding large amounts of fuel, however, i noticed that in a bit of chop or rougher conditions on considerably shorter trips the economy is much, much worse.

on another note; is there a specific reason as to why you shouldn't travel with the outboard on your SIB? surely the transom would be put under similar pressure on the water bouncing around with the weight of the outboard as it would on the road? do transoms break? can you get transoms reenforced so they can have outboards on them during road travel?

[Clipper]

amazing, 200 views, 2 responses..i guess 1:100 ratio of advice offered is better than nothing??!!

I will be ringing around and enquiring with local boat shops here in Australia and leave you guys to it.

enjoy.

[HUMBER P4VWL]

this is ribnet, not sibnet! What do you expect?

[Poly]

Originally Posted by Clipper

amazing, 200 views, 2 responses..i guess 1:100 ratio of advice offered is better than nothing??!!

I will be ringing around and enquiring with local boat shops here in Australia and leave you guys to it.

enjoy.

Clipper, I thought it was a bit of a rhetorical question - since you stated the facts. It didn't seem totally infeasible to me either, and as mmgarrett says you have a very lightweight/efficient package.

I don't have an identical package to compare - but a 60nm round trip (with only me on board) using a 20HP 2str in good conditions on a 3.9m boat (which is solid so heavier than your SIB) used a little under 30 L of fuel. It wasn't sitting at WOT all the way but it was close to it to keep up with two faster boats. So that seams to be consistent with your friend's fuel consumption. Your own boat does seem to have been particularly efficient - and/or your estimate of the amount of fuel you used is not very accurate (e.g. I find that I can get more than 25L in my '25L tank'.

As for why you got 200 views but only "2 responses". Firstly I don't think you made it clear that you had a specific question, rather than just reporting on a great day out. Secondly I wouldn't read too much into the number of views - I am sure it includes the automated search engine spiders which are constantly trawling the site looking for posts.

Originally Posted by HUMBER P4WL

this is ribnet, not sibnet!

well it was posted in the "SIBs" sub forum - a section that was created because of the large number of people with smaller boats and small engines.

What do you expect?

Everyone to be treated with respect regardless of the size of boat they own!

[Poly]

Originally Posted by Clipper

on another note; is there a specific reason as to why you shouldn't travel with the outboard on your SIB? surely the transom would be put under similar pressure on the water bouncing around with the weight of the outboard as it would on the road? do transoms break? can you get transoms reenforced so they can have outboards on them during road travel?

I'm sure this has been specifically discussed before. I don't think on a SIB with small engine the problem is with the transom breaking but rather the wear on the joint between the sib and the fabric. I guess the boat is supported quite differently when in the water (or bouncing in and out) compared to on a trailer. If it was mine I would have no worries about short trips on good roads.

[willk]

Originally Posted by Clipper

amazing, 200 views, 2 responses..i guess 1:100 ratio of advice offered is better than nothing??!!
I will be ringing around and enquiring with local boat shops here in Australia and leave you guys to it.
enjoy.

Originally Posted by Polwart

As for why you got 200 views but only "2 responses". Firstly I don't think you made it clear that you had a specific question...

I can help answer part of your question, four of the views were me and I thought you were just bumming about how little fuel your boat used. My granddad used to do this about his 2CV, and I learned then not to fall into the trap of replying.

I'm still not sure what "answers" you wanted? Someone to say "Strewth Mate, you've got a magic engine!"? Maybe you should actually measure the amouint of fuel used before asking?

Given your hissy fit, I'd guess one of your crew pissed in your tank when you weren't looking...

Incidentally, don't be fooled by Polwart's placatory reply to you, when he's not Moderating me, he's the green Data Dude on Star Trek - programmed to be reasonable

[Poly]

Originally Posted by willk

Given your hissy fit, I'd guess one of your crew pissed in your tank when you weren't looking...

Incidentally, don't be fooled by Polwart's placatory reply to you, when he's not Moderating me, he's the green Data Dude on Star Trek - programmed to be reasonable

mmm.... I don't watch Star Trek - but I might be getting myself an Avatar!!!

[Downhilldai]

Originally Posted by willk

Given your hissy fit, I'd guess one of your crew pissed in your tank when you weren't looking...

I wondered whether there may have been a jack onboard, who, when everyone else wasn't looking, took the opportunity to decant (pinch) some of the fuel from the other boat into this one.

[Clipper]

wonderful, a forum with cranky people who are familiar with sarcasm... stick with it willk it may be the lowest form of wit but somehow i feel your a master of it.

my question was purely that:

"on another note; is there a specific reason as to why you shouldn't travel with the outboard on your SIB? surely the transom would be put under similar pressure on the water bouncing around with the weight of the outboard as it would on the road? do transoms break? can you get transoms reenforced so they can have outboards on them during road travel?"

note the question marks.

not specifically whether people believe my apparent outlandish claims on fuel consumption. certainly not planning to try to fill the tank to justify my observations. i filled it up over the 25l mark, tipped it on it side to get as much as i could in there, and its certainly not much below the 25l 'safety margin' now.

thanks for the reply polwart, some people (such as me) are a lot less experienced than those on this forum and its nice to get a solid answer, and to have what should be a great resource via the world wide web. unfortunately people learning still (me) have to sift through the lame jokers who think their mocking comments are somehow clever, or smart.

[Poly]

Originally Posted by Clipper

wonderful, a forum with cranky people who are familiar with sarcasm... stick with it willk it may be the lowest form of wit but somehow i feel your a master of it.

my question was purely that:

"on another note; is there a specific reason as to why you shouldn't travel with the outboard on your SIB? surely the transom would be put under similar pressure on the water bouncing around with the weight of the outboard as it would on the road? do transoms break? can you get transoms reenforced so they can have outboards on them during road travel?"

note the question marks.

not specifically whether people believe my apparent outlandish claims on fuel consumption. certainly not planning to try to fill the tank to justify my observations. i filled it up over the 25l mark, tipped it on it side to get as much as i could in there, and its certainly not much below the 25l 'safety margin' now.

thanks for the reply polwart, some people (such as me) are a lot less experienced than those on this forum and its nice to get a solid answer, and to have what should be a great resource via the world wide web. unfortunately people learning still (me) have to sift through the lame jokers who think their mocking comments are somehow clever, or smart.

Clipper - I would generally recommend starting a new thread when asking a whole new topic - as people who have skimmed the original question and thought it irrelevant may have something to add. Also not everyone reads every post/thread so you need to use a title that tells people immediately if this is an area they may have an interest/something to add, so your original thread may have got a better response with:

"Surprisingly low fuel consumption - anyone found this?" or "Fuel consumption - 18 HP Tohatsu 2str"

Whilst your suplimentary question would be better in a thread "Towing SIB with engine in place".

However the way to get people to help you is probably not to complain if they don't... nobody here owes you an answer.

[m chappelow]

i must admit when i bought a 4 stroke after being used to 2 strokes for decades i was surprized at how little fuel it used ,i normally use it on a heavy hard displacement boat so top speeds down to around 6 knots but it will run forever on a tank full ,,even when i put the engine on my s.i.b. and have a buzz here and there in the lumpy stuff for a couple of hours or so about the fuel consumptions next to nothing.,,i tend to spill more than i use when filling the tank ,,,,with an inflatable get the boat weight right ,boat up on the plane and engine throttle/revs to around 70% or 3/4 and it should be running at its best so no suprize.

[Bigmuz7]

Originally Posted by Clipper

wonderful, a forum with cranky people who are familiar with sarcasm... stick with it willk it may be the lowest form of wit but somehow i feel your a master of it.

some people (such as me) are a lot less experienced than those on this forum and its nice to get a solid answer, and to have what should be a great resource via the world wide web. unfortunately people learning still (me) have to sift through the lame jokers who think their mocking comments are somehow clever, or smart.

Emm .. I think its actually called a sense of humour

Originally Posted by Polwart

However the way to get people to help you is probably not to complain if they don't... nobody here owes you an answer.

Indeed .. and infact there are probably more people willing to help here than in many other forums I could name

As to your question .. you seem to have acheived what many aspire to, regards your fuel consumption,.. your boat hasnt broken down .. whats to worry about ?

[raymillard]

I don't think outboard economy is to do with distance covered, more than to do with time run.
For a 2 stroke, the formula, such as it is, says that for every 10 hp, you use a gallon an hour at full (ish) chat. So an 18 hp would be just over a gallon and three quarters an hour.
I run a few 2 strokes, ranging from 3.5 hp to 15 hp, and the formula seems about right.

[willk]

Originally Posted by Polwart

mmm.... I don't watch Star Trek - but I might be getting myself an Avatar!!!

I don't either, but I found you one anyway.

I set the phaser on "Snip" for you

[Bigmuz7]

Hehe ! Bloody perfect willk "If you do not conform .. your post will be neutralised" and .... "I might enjoy it" .. with a slightly camp Mr Humphries look

[willk]

Originally Posted by Bigmuz7

Hehe ! Bloody perfect willk "If you do not conform .. your post will be neutralised" and .... "I might enjoy it" .. with a slightly camp Mr Humphries look

Well I hope he snips you first ya big Blether! He won't use it now 'cos you laughed at it...