Targa 34 fuel consumption?

[cliffdale]

I have a chart showing fuel consumption and speed for
2500rpm, 21.3k, 56lph,1.71mpg
3035rpm, 28.4k, 72lph, 1.78mpg
3700rpm, 36.7k, 101lph, 1.64mpg
3920rpm, 41.2k, 114lph, 1.63mpg

Has anyone got figures for the lower rpm, say when making 6 knots
8 knots
10 knots?

I'm just thinking that if I was running short of fuel, what is the most fuel efficient speed to travel at?

KAD 300s

 

[Whitelighter]

I dont have it for the T34, but I have done extensive research using the Bavaria 330 a few years ago. They are similar boats with similar weights so slow speed condumption, while not identical is likely to be pretty similar.

I found that at very low speeds it was more efficient to run on one engine. With a neutral tide, my figures from tickover to 6 knts are as follows:

One engine running

2.6knts 3.81mpg
3knts 3.47mpg
4knts 3.32mpg
5knts 3.19mpg
6knts 3.04mpg

With both engines

3.2knts 3.21mpg
4knts 3.06mpg
5knts 2.91mpg
6knts 2.78mpg

I found that much over 6knts and you started to push wake and the fuel consumption got progressivly worse.

15knts was the worst apart from WOT, and recorded an mpg of 1.03mpg. Cruise in that boat was anywhere between 2500rpm and 3100rpm (25-30knts) which was a steady 1.9mpg

 

[Dorset Dan]

I have a chart showing fuel consumption and speed for
2500rpm, 21.3k, 56lph,1.71mpg
3035rpm, 28.4k, 72lph, 1.78mpg
3700rpm, 36.7k, 101lph, 1.64mpg
3920rpm, 41.2k, 114lph, 1.63mpg

Has anyone got figures for the lower rpm, say when making 6 knots
8 knots
10 knots?

I'm just thinking that if I was running short of fuel, what is the most fuel efficient speed to travel at?

KAD 300s

Sorry for the thread revival but I am interested in hearing from any other Fairline Targa 34 owners out there.

I have just gone back in after annual maintenance. I have had props sent off to be re-balanced at steel developments, volvopaul has done the valve clearances and usual engine/outdrive servicing, plus we have a nice clean bottom with fresh antifoul.

I was hoping to get to the magic 40 knot mark but on flat sea on Monday in Poole Bay, I maxed out at WOT @ 37 knots (did it two ways to account for any tide). I played around with the trim but whether I was at '0' or up '-5' it didn't seem to make any odds to the top speed.

After a quick search I found this thread and my max revs seem to be 3700 which tally with the above data at approx 37 knots. It doesn't achieve 3920 rpm though.

Any thoughts on this? I know that 37 to 40 knots is marginal but I'd like to know that it can get to what it is supposed to......

I have KAD 300's and s/steel volvo penta C6 duo props if that makes any difference.

 

[julians]

If the engines are running as per original spec, and the hull is clean and the props good, then the other things that could cause a lower top speed are:-

- wind resistance - make sure you dont have the canopys up
- additional weight in the boat - Manufacturers top speed numbers will be recorded with no equipment on board, and most likely no water in the fresh water tank, empty holding tank, and a mostly empty fuel tank, and possibly just 1/2 people on board. If your boat has all the usual kit on board, plus, fuel,water,full holding tank, that could easily account for the difference.

 

[Dorset Dan]

Engines surveyed well last year, props have been sent off to Steel Developments for a re-furb and re-balance so should be all good.

Not too much kit on board (bedding, plates, cups, kitchen utensils, box of spare filters/belts, tender on davits plus a two stroke outboard on a bracket in engine bay).

We had three quarter full tanks of fuel and water so I guess this would have made a weight difference. Canopy screen front and rear were down but sides and top left up.

I was more wondering whether any T34 owners have got to the optimum trim position and whether this will add on those couple of hundred RPM that it's not yet achieving? I did read elsewhere that once it's up on the plane, the T34 is not as trim sensitive as others.

 

[Portofino]

Adding to Julian’s ^^^
In the higher speed ranges the resistance due to wetted surface friction is the largest single element in total resistance or drag , and every effort should be made to minimise it .

Few years ago I was at the Sunseeker factory and noticed they launch and seatrial un antifouled boats .
As well as testing for weeps n seeps they do the performance tests on a plane gel coat .
Near to the Del date they haul out clean and paint / antifoul and charge extra btw .

Also there’s natural aging of the now old engines not quite making the Hp they used to do , poorer valve fit , wear in the timing gears , slightly not quite new injector tip spray pattern etc - all within tolerance but not as good as new .

Bit as said by Julian’s the biggest killer to planing boat speed - under your direct control is wieght - yup Kgs , the rest you can,t really do much about .

 

[julians]

your kit list is a significant amount of weight, presume there is also fenders, ropes , canopies,covers (even if not being used I presume they are stored on boat somewhere).

With the kit and the full water , 3 quarters full fuel, plus the top and side canopies being deployed, I'd guess this is where your missing speed is.

Easy way to check you have trimmed the drive correctly is to trim the drive all the way down/in, accelerate to top speed, then start to slowly increase trim bit by bit, speed should start to increase again as you trim out, stop trimming out once the speed stops increasing. That is your optimum trim for max speed. My optimum trim for max speed (not on a T34, so not comparable for you) is at +2 deg, but the handling starts to get a bit twitchy.

In most boats you should also have the trim tabs retracted all the way up for max speed - I say most boats, as I guess some might benefit from some trim tab, but most of the time having any tab down will increase drag and decrease speed.

 

[Dorset Dan]

Just thinking about it, the tender standing on davits at the back can't help as it will definitely catch some air (it's not quite upright, it leans forward a bit on stand off arms). I can imagine that driving a car at 40 mph+ with something hanging off the back would be noticeable.

I will try again with say 1/4 tank of fuel and leaving the tender and outboard at the marina, taking all covers down, etc to see how I get on and I will try what you say regarding adjusting the drive trim levels and trim tabs all the way up.

 

[volvopaul]

Hi Daniel with another 200 rpm you will easily hit 40 knots , your down on rpm for a start so I’d say the turbos are worn not giving the correct boost .

 

[Dorset Dan]

Anything we can check next time you are here to assess the condition of the turbo's? Would it be probable that both turbo's show equal signs of wear (i.e. with only one worn turbo, would one engine not rev higher than the other to achieve 3,900+ rpm, or is there something that regulates each engine to have equal rpm?)

I appreciate any insights as always!

 

[volvopaul]

Next time your out on her disconnect the sync button it’s the one with the = emblem and blue light this will allow engines to pull what they can achieve, you might find one is quicker than the other .

 

[acbruce]

Quite a few years now since I had a T34, wonderful boat. I got 40knts wide open in Southampton Water on many occasions, showing approx 4000 rpm. The boat was new but it certainly is true that it is a true 40knt boat.

 

[Dorset Dan]

I will try that next time I'm out Paul and report back if one engine pulls more revs than t'other.

And thanks acbruce, that is good to know and tallies with the original reviews that I have read online.

 

[CLB]

Sorry for the thread revival but I am interested in hearing from any other Fairline Targa 34 owners out there.

I have just gone back in after annual maintenance. I have had props sent off to be re-balanced at steel developments, volvopaul has done the valve clearances and usual engine/outdrive servicing, plus we have a nice clean bottom with fresh antifoul.

I was hoping to get to the magic 40 knot mark but on flat sea on Monday in Poole Bay, I maxed out at WOT @ 37 knots (did it two ways to account for any tide). I played around with the trim but whether I was at '0' or up '-5' it didn't seem to make any odds to the top speed.

After a quick search I found this thread and my max revs seem to be 3700 which tally with the above data at approx 37 knots. It doesn't achieve 3920 rpm though.

Any thoughts on this? I know that 37 to 40 knots is marginal but I'd like to know that it can get to what it is supposed to......

I have KAD 300's and s/steel volvo penta C6 duo props if that makes any difference.

A change to C5s will get you the extra RPM, but I doubt it will change your top speed much, if any. Have you tried going into + figures on your trim? My boat runs best at about -2 but my previous boat needed +3 to get best speed.

In the scheme of things, I really wouldn't worry about it. Your max rpm is within tolerance and who really needs 40 knots in a cruiser anyway?

 

[Dorset Dan]

Thanks CLB, you are probably right on the not something to worry about point.

This was particularly bought to mind last night when out on a friends boat (twin D6's) when coming down off the plane there was a horrible sound coming from the engine bay, a smell (like burning clutch) and a lot of rubber fragments upon inspection. Limped back in on one engine. Reminds me that there is more to worry about and should appreciate all the times that the engines are running well as this is worth far far more than a couple of knots at the top end.

Having said that, I will still try volvopauls advice of pressing the button on the EDC panel and running each engine to their own rpm to see if one is pulling higher than the other. Will also play about with trim + / - to see if it makes any difference.

 

[gjgm]

Sorry for the thread revival but I am interested in hearing from any other Fairline Targa 34 owners out there.

I have just gone back in after annual maintenance. I have had props sent off to be re-balanced at steel developments, volvopaul has done the valve clearances and usual engine/outdrive servicing, plus we have a nice clean bottom with fresh antifoul.

I was hoping to get to the magic 40 knot mark but on flat sea on Monday in Poole Bay, I maxed out at WOT @ 37 knots (did it two ways to account for any tide). I played around with the trim but whether I was at '0' or up '-5' it didn't seem to make any odds to the top speed.

After a quick search I found this thread and my max revs seem to be 3700 which tally with the above data at approx 37 knots. It doesn't achieve 3920 rpm though.

Any thoughts on this? I know that 37 to 40 knots is marginal but I'd like to know that it can get to what it is supposed to......

I have KAD 300's and s/steel volvo penta C6 duo props if that makes any difference.

Kad 300s stopped production 13 years ago..I don't know but would you still expect the original full output from the engines?

 

[Dorset Dan]

Kad 300s stopped production 13 years ago..I don't know but would you still expect the original full output from the engines?

Hence the post......

 

[volvopaul]

Kad 300s stopped production 13 years ago..I don't know but would you still expect the original full output from the engines?

Yes , they loose power on turbo wear and faulty 2 stage fuel injectors, fit new turbos and injectors and see full power back on tap.

 

[gjgm]

Yes , they loose power on turbo wear and faulty 2 stage fuel injectors, fit new turbos and injectors and see full power back on tap.

Interesting..thanks..though an expensive 3 knots!!

 

[Dorset Dan]

Interesting..thanks..though an expensive 3 knots!!

That's what I am thinking - that's a lot of £££ for marginal gains but would be interested to know if any other T34 owners with KAD300's of that era are still getting 40 knots.

Any idea of approximate cost of OEM turbo replacement?

And with injectors, I see that they can be removed / tested so presumably if test results are good then no need to change? And dare I ask what cost of change might be?