Old girls fuel economy, sucking juice like its the 1990's

[gazza2006au]

new to me old rig including the 1990 model 30hp Yamaha the 3 cylinder oil injection version

over the past few days me and a mate done most of the running around about 16km's than 4 of us on board done a further 9km's

this little motor has used around 20 litres of fuel, i know the amercians go by 30hp = 3 gallons per hour which = 13.5 litres

just seems like tossing in a 3rd cylinder these little motors guzzle the fuel, now u might be saying 20 litres is FAR but i want to do lengthy trips outside and worried i might run out of juice right behind the bommie

now my boat is jammed with all safety gear etc.. so no place really for a jerry can or spare fuel tank that will only get in the way

what are other peoples fuel economy like with the 2 cylinder 25/30hp motors? i was told my motor just had a rebuild it looks like it but the fuel economy is down the giggler with this two banger

[aussiebasser]

Are you driving it at full throttle, trying to get there quick with 4 on board?

[aussiebasser]

Also, American gallons are smaller than our gallons. 3 American gallons are not 13.5 litres.

[Dan5]

So you are saying 1.25ltrs per 1 km yes?....

A bit of a comparison for you..........Today I went for a run in an 8 something meter Stabicraft hard top with air con running 2x200hp Hondas sitting on 50kph cruise we were using 1ltr per 1km according to the gauges.

We also had 4 people on board........your just missing 370hp and 5mtrs of boat that's all.

[gazza2006au]

aussiebasser about 75-80% throttle with 2 or 4 people

dan im not sure if i could put a 4stroke on my transom it maybe a little heavy for my boat but im liking those numbers your getting compared to my motor

i may have to start saving again and possibly buy a new motor over winter

[Crocodile]

Hello Gazza,

more information please.
What boat?
How fast does it go?
Do you need to use full throttle all of the time?
Are you sure that the rebuild was done properly and that the motor is in a correct state of tune?

[gazza2006au]

Hello Gazza,

more information please.
What boat?
How fast does it go?
Do you need to use full throttle all of the time?
Are you sure that the rebuild was done properly and that the motor is in a correct state of tune?

Hi Croc

unknown hull but heres a picture boat is 4.3m tinny

speed i would estimate around 35kph

i can use 75-80% throttle but 100% helps

i checked the prop last night and tried to look up the stock prop sold with the Yamaha 30hp but couldnt find it, my prop is 9 7/8 x 13 do u think the pitch is excessive? with 4 people on board it does cavitate when turning even the slightest bit

me and my mates probably weigh 100kg's each x 4 people

[Kondo 1]

I have an old 4.1 with a 50hp Yamaha 3 cyl, at half throttle, 20 odd knots I used to be able to run from Nudgee, fish Mud, then the Sandhills and get back to Nudgee basically running a 24l Yamaha tank dry.

Sometimes I would make it, sometimes not quite (had 2 tanks) but at guess that is about 35-40 nm, at full throttle would double my consumption for only an extra 8 or knots.

This is going back a little while before I had all the fuel monitoring and all that so it isn't entirely accurate but may give you some idea.

I also used to run a 12inch prop I think, so maybe you are over propped and using throttle to compensate, 2 strokes do like a drink at full noise.


Sent from my iPad using Tapatalk HD

[scottar]

me and my mates probably weigh 100kg's each x 4 people

Ummmmm 4.3 metre boat, 4-500 kgs of punters and gear - what do you expect from the poor little donk. It's working it's guts out.

[gazza2006au]

i actually think the 30hp motor does well its not a speed demon but does plane with the hydrofoils at around 15kph so at around top speed of 35kph i think its going ok, i really dont want to upgrade horse power without knowing the boats capacity

do u think a SS 10x9 will run my motor better? i can pick one up cheap but im running a 9 7/8 x 13 at the moment

i know jack all about propellers...and i dont have a RPM meter on my boat to tell what its running at now

[robothefisho]

13 pitch is definitely over propped for wat you are doing. Suggest you get hold of an 11 pitch or so.

Also have a ss 11.5 p prop you could try/buy if you want. Just pm me.

[rtp1984]

I have a tohatsu 30hp for sale in great condition if you are looking to replace. It is still fitted to my 4.3 if you wanted a test run.

Cheers rob

[gazza2006au]

PM sent Rob

rtp, im in Sydney a bit of a mission to brissy, iwould need to sell my motor to afford another or even consider a new motor

anyone know the stock propeller size that came with my motor?

[scottar]

Get a tiny tach. Then you will know exactly where you're at

[gazza2006au]

Good idea scottar just had a look for some of the chinese hour/tacho meters