fuel consumption/revs/speed

[rhino_mac]

It was my boat you looked at - we had a chat on the phone about boats at the time.

I think the guy that bought it from me decided to keep it for another season. I met the broker at Clipper Marine at the Poole Boat Show and it was one of his relatives that owned it.

Don't worry about the amount of trim tab you're using initially to get on the plane. Without full trim I just used to bury the swim platform. Just make sure you bring them back when on the plane and trim them out so the boat doesn't heel to one side. Gauges help with this!

 

[lionelz]

It was my boat you looked at - we had a chat on the phone about boats at the time.

I think the guy that bought it from me decided to keep it for another season. I met the broker at Clipper Marine at the Poole Boat Show and it was one of his relatives that owned it.

Don't worry about the amount of trim tab you're using initially to get on the plane. Without full trim I just used to bury the swim platform. Just make sure you bring them back when on the plane and trim them out so the boat doesn't heel to one side. Gauges help with this!

Yep i remember did you get another boat now your other issue is sorted. Get rid of you car boat much more fun☺

 

[Drewster]

http://www.boat-fuel-economy.com/outboard-fuel-consumption-liters
this may help

 

[MapisM]

by lowering the trim tabs i go faster ((no change to engine revs)

That's weird, didn't you mean by chance no change to throttle position instead?
In a boat like yours, getting lower/higher rpm and speed depending on the trim and tabs position without touching the throttle is absolutely normal.
And as also common sense suggests, the trim/tabs combination which gives you the higher speed and rpm, for any given throttle position, is the most economical one in terms of fuel burn.
Whether that is achieved with lowered tabs, it doesn't mean anything, because the additional tabs drag is obviously more than compensated by the better hull asset - otherwise you wouldn't achieve a higher speed, to start with.
But a speed increase with no rev change at all doesn't make much sense.

That aside, the general rule is that any properly designed hull should give optimal performance at cruising speed with neutral tabs (level with the hull) and horizontal outdrive.
Unfortunately, that's not always the case, because these boats are typically available with a wide choice of power (hence different weight, weight distribution, etc.).
Without knowing your particular model, I think it's safe to guess that your power option is among the lower available, and that the same hull can also be fitted with some lighter but more powerful petrol engine.
And of course, you would experience a much more reactive behaviour with such setup - horses for courses.

All that said, I would second rhino_mac view: also my gut feeling is that there's nothing wrong with your boat, based on the specs you mentioned.

 

[lionelz]

That's weird, didn't you mean by chance no change to throttle position instead?
In a boat like yours, getting lower/higher rpm and speed depending on the trim and tabs position without touching the throttle is absolutely normal.
And as also common sense suggests, the trim/tabs combination which gives you the higher speed and rpm, for any given throttle position, is the most economical one in terms of fuel burn.
Whether that is achieved with lowered tabs, it doesn't mean anything, because the additional tabs drag is obviously more than compensated by the better hull asset - otherwise you wouldn't achieve a higher speed, to start with.
But a speed increase with no rev change at all doesn't make much sense.

That aside, the general rule is that any properly designed hull should give optimal performance at cruising speed with neutral tabs (level with the hull) and horizontal outdrive.
Unfortunately, that's not always the case, because these boats are typically available with a wide choice of power (hence different weight, weight distribution, etc.).
Without knowing your particular model, I think it's safe to guess that your power option is among the lower available, and that the same hull can also be fitted with some lighter but more powerful petrol engine.
And of course, you would experience a much more reactive behaviour with such setup - horses for courses.

All that said, I would second rhino_mac view: also my gut feeling is that there's nothing wrong with your boat, based on the specs you mentioned.

No change in throttle and.no change in rev either if so vey minor and not noticed on my counter. But thanks for all other info really useful.

Well i have completed my trip now (photos to come) i done 145 nm with about 6.5 hours 3000rpm as standard and took on 254 ltrs if i have worked that out at just under 40 ltrs an hour or 1.8 ltrs a mile. The strange thing is before i went away done same process had 9 hours running 148 nm and took on 264ltrs the speed and revs very different and a lot of pottering around. Overall im happy would off liked to have used slightly less fuel maybe 30 ltrs less on holiday and i would have been very happy. As for trim tabs i will continue doing what im doing and try to get the best speed for minimum revs as i presume that will give me best fuel economy