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In A World Of His Own
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Discussion Starter · #1 ·
hi...dont answer this if you thing its daft..but i was in the ob dealer yesterday and he told me i should give my boat full throttle to get it on the plane and then ease back..but without tilt and trim the boat wont perform to its optimum,,well i dont give it full throttle but just take it to 13 knots.. is this why i am using more fuel than i think i should..
 

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I would have said 13 knots seems a little slow for your boat and it might be almost off the plane. Try cruising at 17 knots and see if your economy increases.
What's the top speed you can obtain out of interest?
 

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Andy i would of said give it full throttle and then back it off untill about 20 knots and you will be flying along and getting good fuel economy





ETEC
 

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full throttle then drop back to about 17 knots. but if its a bit rough i doubt you will be able to run at 17kts. in a flat sea i would give her full throttle and then drop back to about 3/4 throttle this should give you decent economy.
 

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hi...dont answer this if you thing its daft..but i was in the ob dealer yesterday and he told me i should give my boat full throttle to get it on the plane and then ease back..but without tilt and trim the boat wont perform to its optimum,,well i dont give it full throttle but just take it to 13 knots.. is this why i am using more fuel than i think i should..
Have you tried different settings on the tilt pin Andy? You may have too much negative trim? It might go better a hole or two out? My old boat had no trim. One hole up from full in made a big difference.
What is the consumption like anyway? 13 knots though is more rough weather speed on a planing boat like yours. That will drink fuel at that low speed. You are pushing "through" the water not getting on top of it on the plane.

I see the hacksaw hasn't been used on the cuddy then?:whistling
 

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Looking at that photo and it may well be deceptive due to the waves but you are bow heavy.

You need to trim the boat, bow up slightly IMHO. You then use full throttle to pop out onto the plane theen back off to cruising speed. For you boat I would guess that woud be 20knots ish. Again guess work but I would expect 3/4 litre per mile at that speed, so 10 miles to mark on plane would be just over a gallon.

Slow pop out to plane wastes fuel so WOT would seem good advice to me, then back off to cruise at the most economical speed and there is only you that can find that particular sweet spot. It equates to more miles for the buck so down to you.
 

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I've always been told to open up and drop back Andy, saves fuel and gets you up on the plane easier, i do this and drop back to 16 knots which keeps me on the plane, so like the others have said, 17-20 looks about right for you.

As Dave said though, on my old outboard i had to have the trim pin 1 hole out to get it to perform the best, but even more may be needed for your planing hull, my boat is a semi planing hull. But always conditions have to suit obviously.

Again, it might look deceptive, but looking at the way the actual outboard is sitting in the picture it looks like it isn't trimmed out at all??


Mark
 

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In A World Of His Own
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Discussion Starter · #8 ·
hi ..it only does 16 knots wot but it needs a bottom clean..i have only a 40 hp ob.and doing 13 knot is what i do.. the tilt pin needs to go out to to the sea or back towards the boat?
why does it seem bow heavy...is something not right?
 
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hi ..it only does 16 knots wot but it needs a bottom clean..i have only a 40 hp ob.and doing 13 knot is what i do.. the tilt pin needs to go out to to the sea or back towards the boat?
why does it seem bow heavy...is something not right?
It's probably full of water between the skins,Gangling osmosis,acting like a sponge and about to sink at any time :unsure:......Or you have probably got too much crap in the cabin! For God sake Andy dont start worrying about the head being down a bit!!
 

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I think it`s just the way it looks with the waves in the picture as there is nothing heavy up front as far as I know.

The boat hasn`t been antifouled for nearly two years so he is flogging a dead horse really where speed is concerned.

The boat is performing nowhere near how it could be.


Alan
 

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hi ..it only does 16 knots wot but it needs a bottom clean..i have only a 40 hp ob.and doing 13 knot is what i do.. the tilt pin needs to go out to to the sea or back towards the boat?
why does it seem bow heavy...is something not right?
Have you tried the prop calc program? http://www.castlemarine.co.uk/pitch.htm
You'll need to know your max prop diameter, gearbox ratio and boat weight but with a few (wildly) guessed numbers it looks like your boat should top out well over 20kts.

Also, bit of a long shot but are you sure you are not carrying a load of water in the buoyancy or between the skins? Are there any holes in the skin - deliberate or otherwise - like through the hull fittings or keel bands which could be leaking? Also are you sure rainwater is not getting into the void? (Assuming it rains down your way!)

Regarding the state of the bottom - I found that a bit of slime makes little difference but once the barnacles start to grow it destroys planing performance. Now the water is at its warmest it's worth a swim with a mask and a scrubbing brush to see if it makes any difference.

HTH
 

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Have you tried the prop calc program? http://www.castlemarine.co.uk/pitch.htm
You'll need to know your max prop diameter, gearbox ratio and boat weight but with a few (wildly) guessed numbers it looks like your boat should top out well over 20kts.

Also, bit of a long shot but are you sure you are not carrying a load of water in the buoyancy or between the skins? Are there any holes in the skin - deliberate or otherwise - like through the hull fittings or keel bands which could be leaking? Also are you sure rainwater is not getting into the void? (Assuming it rains down your way!)

Regarding the state of the bottom - I found that a bit of slime makes little difference but once the barnacles start to grow it destroys planing performance. Now the water is at its warmest it's worth a swim with a mask and a scrubbing brush to see if it makes any difference.

HTH
The boat performs fine with a clean bottom and will get onto the plane no problem with engine the way it is.
The longer he leaves it the worse it will get. He has know this since he first saw the boat.

Alan
 

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hi ..it only does 16 knots wot but it needs a bottom clean..i have only a 40 hp ob.and doing 13 knot is what i do.. the tilt pin needs to go out to to the sea or back towards the boat?
why does it seem bow heavy...is something not right?

Where is the pin at the moment Andy? It may be right as it is.

All the other answers have points that effect what you wan't to do. Which is reduce consumption right? Rev it up and go fast to get a good plane speed then drop back a tad to get it going slower on the plane (much more that 13 k though) and hopefully you get better consumption.

But you need to say were the pin is at the mo to get some info on that?

:clap: A little bird told me Congeraider has been recommending Tohatsu engines to you?
 

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To my mind a 40hp is borderline for that style of hull. Not owned one myself but had similar.

Any of the other possibilties mentioned so far may apply - but without a bit of extra power you will need to get the boat set up to its best to get a fair performance.
 

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all the crap (green stuff) on the botom of my 165 reduced ma top end to 16knotts, causes soooo much friction. cleaned it and put a new coat of antifoul on, 26knotts no problem now!! also alot better on fuel
 

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I would"ve thought that with a clean hull & correct engine trim & prop your package should give roughly 23/25kts max & between 3/4-1 litre per mile cruising IMHO. If the hull is dirty you"re destroying performance & economy.
As I"ve said before Andy I think you"ve got a great package & are nowhere near getting the best out of it either performance wise or in terms of it"s capablity at sea.

headlight
 

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In A World Of His Own
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Discussion Starter · #17 ·
hi there is a hole cut in the floor just below the splash well with a bilge pump set down in it..i have often thought that there is water in the gap i bilge it out as some water gets in down there but i have a cover i have a battery and spare 4 kg anchor up front..the bottom does need cleaning the pin is set in the second one back from the transome


you can see the hole here i bilge it out when in the berth and again when moving as it tilts and runs back any more water in there..this piccie is not long after i got here i have the new battery in a box there now etc
 

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ok andy looks like first job is to scrub her butt , you will be amazed at the differance it will make. then give her 2 coats of antifoul all this can be done in a day. sounds to me like alan is giving you good advice but your not listening.
 

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hahahahaha dont need to read manuals, n drink fuel! lol
 
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