Yamaha F150 High Fuel Consumption

[Stresspill]

I have a Yamaha F150 2011 in my SR6. Yesterday I went for a run that was quite mixed driving, all from going at idle to blasting 40 knots and then also some slow surfing at big swell. My ride was 15,3 miles and I used 19,8 litres. Which makes it 0,77 NM/l. Usually when cruising I get about 1:1 or even a bit more economical.

[Obsidian]

Until this Summer I was constantly getting 1:1 or 1.1:1 lpm.

This is on a catamaran with a waterline length of 16ft, so displacement speed is 4kn, semi is 8kn and minimum planing speed is 12kn. Which ought to be even more frugal than 1:1 in perfect conditions.

[Stresspill]

Yep, should be a lot more economical than my setup.

[Obsidian]

Update on this one!

Having changed about everything.... Gearbox rebuild, injectors, fuel pumps, coils, etc etc.

It looks like the throttle position sensor was out of adjustment!

For the uninitiated, as I understand it, the throttle is air only so in order to inject more fuel the ECU has a sensor and this determines the fuel flow in conjunction with the pulser coil for timing. The sensor has scope for more and less, mine is running very rich.

Cant say anything definitive as my security torx bit snapped off.

But this is the theory of the day.

[charliee]

Hi StressPill, youR fuel consumption was 1.242l/nm, if you plan your trip back to front you may end up short of fuel!

[Obsidian]

Further update:

Having bought a new set of torx, I can confirm that this issue was the throttle position sensor!

It was a 20 minute job to get it set up right, on the berth. Engine on and warmed up, throttle set to 1700rpm in neutral. Loosened the TPS and rotated it one way - engine ran rougher, rotated it the other way and revs picked up... No longer miss firing, no smell of unburnt fuel and no visible exhaust colouration.

Took her for a run out, absolutely beautiful! Loads of power (150HP on a 6m Cat), really responsive. Fuel consumption was 1.1 lpm in sem-displacement and 0.8 lpm on the plane. I suspect with a polished hull .5-.6 would be possible in calm weather.

So big lesson learned! I suggest anyone with a fuel injected engine asks their engineer about TPS adjustment over time, mine was clearly way out.

Two big plusses for me are the ability to run at sub planing speeds for a day on the river without spending £100 on fuel, and range is now >100nm with full tanks (plus reserves of course).

Thanks for everyone's help.

[Searider]

That's great news.

To add to this always look at the "simple" stuff first. If it were an old car with these symptoms what would you look at?
Ignition? Leads, distributer, rotor arm.
Carbs? Adjustment, contamination.
The symptoms you had were of running rich. Remember how poorly a car would run if the choke was left out?

Most fuel injected outboards have their fuel map controlled by throttle position sensor (TPS) and Mannifold Absolute Pressure (MAP) sensor either of which can either come out of adjustment or deteriorate.

[Orwell boy]

Two big plusses for me are the ability to run at sub planing speeds for a day on the river without spending £100 on fuel, and range is now >100nm with full tanks (plus reserves of cour

Pleased your sorted and even more to hear what sounds like such enthusiasm for your nautica boat ,i too have a 19 footer and i find the ride second to none and thats on a single hull and economical too ,mine has a huge tank (246 litres ) and seeing your 100 litres sent me straight to the catalogue http://www.schlauchbootfreak.de/down...5.40-12.50.pdf ,i think your boat has two tanks totaling 48 us gallons = 182 litres ,maybe helpful

[Locozodiac]

Wow, that was a costly troubleshooting, too much parts changed with no avail....

What's the max wot rpm achieved on flat calm water cond if possible to test as currently loaded ? Any marine motor should run at least middle to max wot rpm range factory stated as loaded, once combo is on perfect plane can reduce throttle for best fuel comsumption at cruising speeds. For that to happen motor must be running spot on as a Swiss clock.

Happy Boating

[Obsidian]

Originally Posted by Orwell boy

... i think your boat has two tanks totaling 48 us gallons = 182 litres

The specs in that catalogue are all correct, except for the tank capacity. I believe its even slightly under 50 Ltrs a side, dont think I have ever got more than 40-something in. Would be nice to have the bigger range!

Its is a cracking boat, if I were building one from scratch the only thing I could change is slighter deeper hulls; to keep the tubes out of the water at rest mainly.

[Obsidian]

Originally Posted by Locozodiac

Wow, that was a costly troubleshooting, too much parts changed with no avail....

The injectors needed doing anyway, a spare coil is no bad thing, gearbox was also due an overhaul. So all good.

WOT is 5400, not that it stay there for many seconds at a time

With one up and full fuel she planes on flat water at 2700 rpm, aprox 12 knots. A steady cruising speed is 22 knots, usually achieved by 3400-3600 rpm (book consumption is <20 Litres an hour @3500).

[enzo200500]

Obsidian, did you manage to find a copy of the Service Manual for your engine?

That would give the correct output voltages for the TPS. Might be able to achieve even better performance then!

I thought the Max RPM’s for our 150’s was 6k? I thought you should be closer to that when running just on your own?

[Obsidian]

I checked the cottages and they were out, so replaced the TPS. It didn't seem to make a difference, but its another job done.

I am sure the engine would max out at 6000, but 5400 is as far as I am prepared to lean on the throttle. Thats usually around 40kn and there is very very little boat in the water at those speeds.

[Pikey Dave]

Originally Posted by Obsidian

I checked the cottages and they were out, so replaced the TPS. It didn't seem to make a difference, but its another job done.

I am sure the engine would max out at 6000, but 5400 is as far as I am prepared to lean on the throttle. Thats usually around 40kn and there is very very little boat in the water at those speeds.

Did you try resetting the thatch?

[Obsidian]

Voltages, the voltages were out!