Fuel Consumption

15 posts / 0 new
Last post
Fuel Consumption

Hi all,

We have a 26x with Yamaha F50 4 stroke motor. What sort of fuel consumption should we get? I expect speed will have a bearing but any insight would be good.

We are hoping to spend a week on the firth of Clyde next week and we might end up motoring a lot! So far our experience with long runs of the engine have been limited.


David Kirk
26X Glissando
Dumfriesshire, Scotland

Depends on how fast you go.

Depends on how fast you go. these motors are very economical you can motorsail all day on a tankfull.

On inland waterways at about

On inland waterways at about 18 to 20k revs I have estimated 1 to 1.5 miles per litre. I have Yam F50 high thrust 15 yrs old but serviced annually. I guess sea is something similar but conditions can vary a lot and whether you can get it to plane...? !

X being flatter bottomed and slightly lighter might be better.

Roly, 26M

Hi David, 

Hi David,

I've been having a similar dilemma. The Yamaha F50 consumes 15/18 liters per hour at wot. Always good to think of consumption over time rather than distance.

Main impacting factors are sea state and engine trim. A perfectly flat sea will give you a nice easy motor, where you can tune the throttle and engine to the level you want in power mode. A busy sea might mean you are using much more fuel.

Key thing is to have a spare tank or spare fuel, if you are going to be doing long distances. If it's a new engine/ boat to you I would recommend fuel set as an additive, it's great for the engine and can increse efficiency.

Hope this helps.


Ooo...fuel additive. That's

Ooo...fuel additive. That's interesting. Never done that. How much and how often ? I'd love to improve my engines performance. I used to be able to get 15kn but now only 12.5 max at 53k revs


https://www.amazon.co.uk/dp/B00CISFESK/ref=cm_sw_r_cp_apa_glt_fabc GM0NF...

One bottle will last a long time. 10ml for 10li think. Instructions come with it. That's quite a difference in speed. Same stuff on boat I presume. Is your propeller nice and shiny with no dents? Small nicks in the prop can make a bigger difference than you think.

Am sure there are comments on here around prop pitch/size etc. Not found it yet, but I'm hoping to do some testing this weekend, as I'd love to get a 4 blade stainless steel, as it made a huge difference to my old speed boat. Changing from a 21 Ali 3 blade to a 21 stainless steel 5 blade was just transformational.

Well, I understand that the

Well, I understand that the Yammy 50;is a de- tuned 60 there is advice on the net on how to get that extra 10.

Now that is interesting.

Now that is interesting.

Flat out my F50 4 stroke max

Flat out my F50 4 stroke max out at 4600 rpm which I dont think is enough- so something needs sorting . Best guess from my limited experience is 5 gall an hour flat out, but flat out is not planing and 10/11 knots with ballast in. 4000 rpm is pretty much same speed at less consumption. My prop is a bit rough so that also needs sorting.

The Yam F50 of that era (2005) has a restriction in the air intake that can be removed to make it similar to the 60 version... I will be doing this in next few weeks as an experiment...

rick.jones's picture
Hi Matt

Hi Matt

Sounds like you have a too high pitch prop (a common problem). It's likely 13", 12" would allow higher revs at WOT.

If you're going to get your prop professionally tidied up, they should also be able to re-pitch it by up to an inch.

Rick Jones (Treasurer) 1994 Mac 19 "White Lightning", Isle of Wight

the mac video says that for

the mac video says that for every 100 kilos on board lowers your speed by one knot.