An insurmountable problem??

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ontheplane

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Was down on the boat over the weekend....

Have fitted oversized trim tabs to try and help with the main problem of the boat - its underpowered and has trouble getting on the plane.

They have helped enormously, the boat now planes much much more easily - however not actually much faster!

Whilst it comes up on the plane at lower speed, and I can then raise the tabs and she will still plane, provided the throttle is wide open, throttle back and she'll drop off unless I lower the tabs again.

So I have to accept this boat is chronically underpowered for whizzing about the bay.

I just cannot see any solution other than to re-power, however I have always felt that unless an engine blows up, you are always better off taking the money for a re-power, selling the boat and putting the two amounts together and buying a better / newer boat that is powered how you want it.

However, to buy a 22ish foot diesel cruiser with around 5'10" headroom in the cabin (i.e. not a cuddy) it's gonna cost a lot more than is available....

Does anyone know whether secondhand diesels of around 200hp (perhaps with a drive leg as well as the gearing etc may well be different) ever come up, and if so what kind of costs - because if it's £5000 or so, it's just not viable.

I would only consider re-powering with a petrol (replacing current petrol) if it was an EFi and MASSIVELY cheaper than the diesel - it just doesn't seem worth it otherwise.

Any ideas guys?
 
Only repower if you want to keep the boat for a long time, if you are tottering between yes and no, then don't do it.
The budget will always blow out, especially with installation, and at the end of the day you don't really know what you have brought in the form of a 'pre-loved' engine and drive.

A big 6 cylinder diesel may not suit your boat, at 22ish feet, sounds a bit small.

Good luck, with whatever descision you make.
 
145HP petrol in a 1800kg (dry) boat.

I was always told for decent performance you need 100hp per ton and for really good skiing performance nearer 200hp per ton was the target.
 
have you tried props with less pitch ?
remember that the props have to be impeccable for optimum performance !

agree with andymac, there are alway's unexpected costs and extra's, and the cost of re-engening will "never" increase the value of the boat to the level what it has costed to you.

Of that size there are many boats around in different makes and flavours, the search for another can be very exiting ...

good luck with whatever you do
 
Have you confirmed that your engine is actually pulling maximum revs available?
Another possibility may be to lighten the boat- do you carry a lot of freshwater (beer?), change from all anchor chain to part rope/ do you need all the fuel you can carry/ food for a week/ massive tool box, etc.
On a small boat the extra weight can make a big difference to performance, especially when the power is marginal.
 
Fairline Weekend 21
Volvo AQ145 (140hp) with a 270 leg (single not duoprop)

All above are good points.

The engine pulls around 4500 rpm flat out - which I think is down a fair bit on top whack (5500 is permissable, but max continuous is probably 4800-5000).

My concern is that whilst I agree about reducing weight - the owners do like their creature comforts... to the point that the weight gets piled on. The crazy thing is, that at 4500 rpm we are only making around 11kts - Fairline reckon that as new with this engine the boat was good for 23kts.... Now I realise that's empty boat with no toys - but I can't imagine that an extra 1000rpm would yield up double the speed!

I don't actually know what pitch prop is on there, and I do intend to get this looked at later in the season....

I do think that i've had my question answered though, the thinking seems to be that a re-power isn't on the cards, and I'm better off reccommending a sale and replace boat...... Shame cos no-one's buying at the moment I reckon!

Thanks all
 
With the value of your boat at the moment, its swings and roundabouts. You may sell slightly cheaper, but you can also buy slightly cheaper.

Before you even start thinking down that line, have the boat examined, prop size etc... by someone smart. I'm sure the guys on the forum can recommend a local guru.

Good luck
 
I agree; a finer prop is needed or your engine is out of tune, or mebbe just 'tired' due to age? Once up on the plane speed picks up rapidly for every extra 100 rpm. With my boat 3100 rpm is 17 knots, 3600 rpm is 25. If you can achieve max rpm you may well get to 20knots.
 
Don't think your down in rev's your just not getting onto the plane so the engine cannot rev freely, I think you've been through all this before on here but nearly every 21-23ft small sports cruiser sold in the 70's and 80's with a Volvo 145 was underpowered and doesn't plane very well today, best change the boat and sell it to someone on a river.
 
Hello, I had a fairline weekender up until about 4 years ago. I bought her with a Volvo 120hp petrol & like you, found she struggled. I loved the boat to bits & spent a great deal of time re-fitting the inside as a project. I eventually decided to bite the bullet & re-power. After much homework I decided upon a Volvo 170hp Kad32 diesel. The effect was nothing short of breathtaking-open the throttle, a little delay whilst the supercharger cut in & then it was like being punched in the back right up to around 32-33 knots!! I had her for around 5 seasons & she proved to be a fantastic little boat. I would recommend a similar conversion to anyone as long as you plan to keep the boat for a while. I can assure you that you will never recover the outlay when selling, but for me this was far outweighed by the sheer fun factor I had with her.
 
All of this sounds very familiar...from an owner of an old heavy boat of the early 70's with an AQ115....

If I'd only know this sort of stuff before I started a year and a bit ago /forums/images/graemlins/smile.gif Oh well, hind sight is a wonderful thing /forums/images/graemlins/smile.gif

Maybe the panel could comment whether something like this would help at all ??

I'm personally going to have to try and track down a fine pitched prop for a 100 leg....no mean feat I can tell you.
 
I had a 23ft with 231hp V8.First time out, I filled her 3/4 full and it wouldnt plane.
11 knots isnt planning so your not skimming along out of the water yet.
Solutions.
1. Weight..I only fill mine with 50- 80 litres now.I keep a 20 litre reserve tank up front in case.Only fill up what you need + a contingency.I removed all unnecesary weight,
Bedding,water tank,Fridge,etc and only take the essential baggage with us.A kilo hear and there adds up.dont ditch the safety though.I keep the passenger numbers down!
If boat is loaded, get passengers to go forward until on the plane.

2.Remove all anti fouling and polish the hull.Keep it waxed underneath as it makes it slippery through the water.This was worth 7 knots top end for me.

3.A bloody good service gains Horsepower.Make sure the fuel filter,inc the carb fuel filter are clean.Service the Carb.Make sure there is a good flow of water through the block as Heat robs Horsepower especially at inlet manifold and carb area.

4.Make sure there is good supply of air to the engine bay.

5.Play with the prop as others have said.

6 Get engine rebuilt.If its getting on a bit,Its probably only pushing out 80-100hp now.A fresh engine and a bit of headwork will get you back up to 140hp +.

7. If you dont have trim tabs,they help enormously.

8.Is the carb at Wide open when throttle control is fully forward?

I could go on...There is always a solution to a problem.
 
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