Very Unscientific Fuel Useage Comparison.

[Mollers]

The SR4 has been clocked at 29.5knts when running alongside DHD pulling around 5600rpm. The Missus and I blatted about with it a fair bit on Sat, at WOT or close to. For the day, she used 20ltrs.

I'm not sure, but I suspect, that if we'd covered the same distance at similar speeds 25-28knts with the Vmax (250Etec), we'd not have burnt a great deal more fuel. I need to check the ltr/h figures on the big one at tootalling speed.

[Hambleite]

Well, for comparison, the Scorpion 6.5 with a 150 optimax, at 27knots, 2 up, full tank (165litres) will burn around 23 litres per hour, according to the smartcraft gauges.

They seem to be quite accurate when compared with 'actual' amount of fuel put in and 'amount burned', according to the smartcraft gauges.

32 knots is around 30 litres per hour

42 knots is 59 litres per hour

[Mollers]

Originally Posted by Hambleite

Well, for comparison, the Scorpion 6.5 with a 150 optimax, at 27knots, 2 up, full tank (165litres) will burn around 23 litres per hour, according to the smartcraft gauges.

They seem to be quite accurate when compared with 'actual' amount of fuel put in and 'amount burned', according to the smartcraft gauges.

32 knots is around 30 litres per hour

42 knots is 59 litres per hour

@25knts?

[Searider]

Only getting 29.5 knots with 50hp?

Are they small horses?

Get 26 knots with 30hp on our searider. Big stinky Yamaha horses though.

[Nos4r2]

2 up though. You lose a lot of oomph once you carry a passenger in a 4m. I used to go from 39 knots solo to 33 with 2 people aboard.

Besides, Mollers needs a shave so he isn't exactly aerodynamic

[Mollers]

Originally Posted by Nos4r2

Besides, Mollers needs a shave so he isn't exactly aerodynamic

She's propped to be a w/board tug and there are only 50 gee gees to play with.

[Nos4r2]

Originally Posted by Mollers

She's propped to be a w/board tug and there are only 50 gee gees to play with.

What's your WOT revs? 5600 sounds low.

You might want a bigger pitch for when I finally get myself in gear to organise the 2010 Searider bash

[Mollers]

Originally Posted by Nos4r2

What's your WOT revs? 5600 sounds low.

You might want a bigger pitch for when I finally get myself in gear to organise the 2010 Searider bash

5500-6000. She'll pull 57/5800ish.
I reckon 31/32 knts would be the most you could squeeze out of it.

[Hambleite]

@25 knots?

Well, the engine seems to have a 'natural' sweet spot at a certain rpm. The engine kinda goes all smooth and runs quite a bit quieter. It just happens to give 27 knots at this rpm.

25 knots requires less rpm but the engine seems a bit 'growly' at that rpm.

The hull seems to like going a bit faster too.

Next time I'm out I'll check the stats at 25 knots.

[Nos4r2]

Originally Posted by Mollers

5500-6000. She'll pull 57/5800ish.
I reckon 31/32 knts would be the most you could squeeze out of it.

That surprises me. Biggles' old sr4 with a Yam 50 4 stroke went almost as well as mine. I seem to remember he was hitting 36 knots without problems.

[Mollers]

Originally Posted by Nos4r2

I seem to remember he was hitting 36 knots without problems.

Really?

[bedajim]

Mine with the 50 thwatsu only saw 30 + on the trailer

+ was wet and uncomfortable in anything over 12" chop, that's why it got sold

[Hambleite]

I'm pretty sure the older 4.0m Searider that searider used to have did around 37-38 knots with 2-stroke 50hp Yamaha. It was a real hoot with 2 up in the low set bucket seats. Until it got lumpy......

It had no power trim but it did have a 'relatively big' prop.

Out of interest the boat that succeeded that one was a 5.4m Searider with a 90hp 2-stroke Mariner did 39.7 knots with a balanced laser11 prop. Can't remember which size but searider knows.

That 'seemed' to burn not much less fuel as the current Scorpion does.

[GordyP]

I actually bothered to try to get a proper handle on what i am using, filled up before i left and refilled on my return and used the trip on the gps. Ran for just under 2 hours, average speed was 30.4 kts and used just under 80 ltrs of fuel. Not too bad for the big lump of boat, 3 divers and full kit including spare cylinders.

[Mollers]

Originally Posted by GordyP

I actually bothered to try to get a proper handle on what i am using, filled up before i left and refilled on my return and used the trip on the gps. Ran for just under 2 hours, average speed was 30.4 kts and used just under 80 ltrs of fuel. Not too bad for the big lump of boat, 3 divers and full kit including spare cylinders.

So halve that for one engine and halve it again for one hours running and we're getting near my little 50 running near WOT for an hour.

[Searider]

Originally Posted by Hambleite

I'm pretty sure the older 4.0m Searider that searider used to have did around 37-38 knots with 2-stroke 50hp Yamaha. It was a real hoot with 2 up in the low set bucket seats. Until it got lumpy......

It had no power trim but it did have a 'relatively big' prop.

Out of interest the boat that succeeded that one was a 5.4m Searider with a 90hp 2-stroke Mariner did 39.7 knots with a balanced laser11 prop. Can't remember which size but searider knows.

That 'seemed' to burn not much less fuel as the current Scorpion does.

It was a 20".

[GordyP]

Originally Posted by Mollers

So halve that for one engine and halve it again for one hours running and we're getting near my little 50 running near WOT for an hour.

I'm almost tempted to offer to swap with you!

[Nos4r2]

Originally Posted by Mollers

Really?

He wasn't far behind mine and solo in flat calm and a light load I used to make 39 knots. It was quite scary though.

[Downhilldai]

I told Mollers he needs to do the zip up on his jacket and get down on the tank a bit more.

[Mollers]

Originally Posted by Downhilldai

I told Mollers he needs to do the zip up on his jacket and get down on the tank a bit more.

Blimey, me in an LJ.

Check out the olive barrel fellow SR owners. A superb addition.