Fairline mirage,advice

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Fairline mirage,advice

Postby seagull2 » Tue Sep 25, 2012 6:27 am

hi people! I am from Croatia and I am owner of fairline mirage 29 for 2 years.Now i am having wondering with my speed..She is 1977,and originaly I belive insida was twin petrol,owner before me had two toyota 4200ccm 136 hp,and people told me that she was braking walls with these twin diesels.and going cruise speed 22-24 knots)After (because he is man in the ages)he removed one engine and put other one in the center,so Now I have mirage with one toyota diesel 136 hp.attached with volvo penta 280 sp outdrive(i think ratio is 1.61:1).With this propulsion I have cruising speed 7.5 knots at 2400 rpm.(engine revs is 3800 and max torque at 2800).when I give max throtle she goes 10.2 knots but aft is going down bow is going up and pulling big wave at the aft.propeller is 15x17.on full throttle revs go up to 3300.I have read some comments that mirage with 80 hp goes 12 knots,Is it possible that I can go faster with this engine?.In some forums i have read that samo mirage with 135 hp volvo penta goes 20 knots max. that why am wondering..thanks ,cheers
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Postby SiFi » Tue Sep 25, 2012 7:28 pm

I don't know if this will help, but the original sales brochure does give a listing of HP verses speeds as listed below:

The brochure can be found here:
http://www.jonesboatyard.co.uk/boat-sal ... -sale.html

This gives shows:
1x 280hp AD40 giving 21knots

I have twin AQ145a engines in my Mirage, so can't help much more than that.
Simon
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hi sifi

Postby seagull2 » Wed Sep 26, 2012 5:12 am

SiFi wrote:I don't know if this will help, but the original sales brochure does give a listing of HP verses speeds as listed below:

The brochure can be found here:
http://www.jonesboatyard.co.uk/boat-sal ... -sale.html

This gives shows:
1x 280hp AD40 giving 21knots

I have twin AQ145a engines in my Mirage, so can't help much more than that.


Sorry but I think you have made a mistake,if I read good this brochure she would go with engine ad40 + sterndrive volvo 280 = 21 knots. and with 280 horsepower I thing she would go 35-38 knots.
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ad40

Postby seagull2 » Wed Sep 26, 2012 5:14 am

But does anybody knows how much hp is this ad40 and is it diesel or gas?
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Postby SiFi » Wed Sep 26, 2012 12:00 pm

Sorry Seagull2, my mistake, the 280 referrs to the Volvo 280 Outdrive.
I don't know the HP. I know it is a diesel.
Simon
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Postby SiFi » Wed Sep 26, 2012 12:09 pm

I've done some searching on the web and found out it is a Penta engine, later renamed to a AQAD40

I've just found this page of info:
http://www.crommarine.com/volvo_penta/v ... ine_di.htm

Maybe this helps?
Simon
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OMG

Postby seagull2 » Wed Sep 26, 2012 1:55 pm

Right now I ve found that ad40 is volvo penta 6 cyl engine with 130 hp,and with this engine mirage fly on 21 knots!! Why mine cannot??my engine is 4200 ccm 136 hp in very good condition diesel ,maybe the problem is strndrive??what possibilities are that the sterndrive is not good,its 280 model single prop,maybe clutch slides?does it have clutch?becaose i dont know much about outdrives inside.. i believe i dont have problem with weight because i ve tried with empty tanks also with full water at bow..a little bit faster go with full water,about 0.5 miles faster..maybe i need to put duoprop?and also my trim tabs are not working but they stay strait as the bottom..
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Postby SiFi » Wed Sep 26, 2012 2:26 pm

From the description in your first post:
when I give max throtle she goes 10.2 knots but aft is going down bow is going up and pulling big wave at the aft

This suggests you either do not have Trim Tabs or that they are not set correctly.

Trim Tabs will keep the bow of the boat down and bring the stern up - allowing your boat to get 'on to the plane' then you will be able to achieve higher speeds.
Simon
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Postby seagull2 » Thu Sep 27, 2012 4:37 pm

SiFi wrote:From the description in your first post:
when I give max throtle she goes 10.2 knots but aft is going down bow is going up and pulling big wave at the aft

This suggests you either do not have Trim Tabs or that they are not set correctly.

Trim Tabs will keep the bow of the boat down and bring the stern up - allowing your boat to get 'on to the plane' then you will be able to achieve higher speeds.[/quote

actualy I have trim tabs but they are not in function they stay at one place and that is strait as the bottom goes..So maybe if I repair them and then try full throttle when bow starts to go up I should move trims down?If she start Flying do I need to return tabs to the center?Oh dear God i pray this is that.I dont need to high speed if She could only get 12-13 knots cruisingspeed I would be more than happy..because 7.5 is to slow..]
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Postby SiFi » Thu Sep 27, 2012 7:31 pm

Correct, trim tabs down = bow down.
:D
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Postby seagull2 » Sun Sep 30, 2012 2:38 pm

does anybody know some mirage with like this profile and her speed?136 hp single diesel...6 cylinders 4200 ccm.
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Postby ms » Wed Oct 03, 2012 12:42 pm

I would say that 15 x 17 props were those fitted to original petrol engines and you wont get much out of one of those until you get 5,000 rpm.

A diesel engine of this power would swing a 16 x 21 without any problem and this would deliver much more thrust. you might even try 16 x 23 (the largest that this leg will take)

Whether this HP is enough to get over the 'hump' and start planning I am not sure - frankly I doubt it.

Currently at high power (and trim tabs up) the boat should take a nose up attitude, and it will become lower once you start planing. Use trim tabs as little as possible as this will lower your speed and therefore maybe prevent planing.
You might find that a little ballast in the bow (I have 100kgs) will help you a little - to bring the nose down a bit without using trim tabs. (I replaced twin petrol 145 with twin turbo diesel 145HP).
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hello

Postby seagull2 » Wed Oct 03, 2012 12:49 pm

ms wrote:I would say that 15 x 17 props were those fitted to original petrol engines and you wont get much out of one of those until you get 5,000 rpm.

A diesel engine of this power would swing a 16 x 21 without any problem and this would deliver much more thrust. you might even try 16 x 23 (the largest that this leg will take)

Whether this HP is enough to get over the 'hump' and start planning I am not sure - frankly I doubt it.

Currently at high power (and trim tabs up) the boat should take a nose up attitude, and it will become lower once you start planing. Use trim tabs as little as possible as this will lower your speed and therefore maybe prevent planing.
You might find that a little ballast in the bow (I have 100kgs) will help you a little - to bring the nose down a bit without using trim tabs. (I replaced twin petrol 145 with twin turbo diesel 145HP).


Thanks for your reply.I also believe that I need bigger propeller,but problem is my leg is short hub and maximum propeller for it is 15x17..16x23 is for long hub.. I think its the best way to get some results for the first is to put 290 douprop for diesels 1.61:1
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Re: Fairline mirage,advice

Postby seagull2 » Thu Dec 20, 2012 5:42 pm

I made some good projects last months,but still need to do more .with this spoiler she stays strait with water, bowdown.and these 2 stabilizators helps much for side waves!Next time when i come home I think where did I make mistake,I need to put 1:2.15 ratio and big propeller 16x21 or?? because now I ve tried with 1:1.61 and 15x15 an full speed is 9 knots..slower than before...
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