stelican
Well-known member
Surely If this is the case the engines are over propped as they are not reaching max revs.
Targa 34 performance
- Thread starter Harpergreg
- Start date
PaulRainbow
Well-known member
MAX RPM is 3,800, OP reports 27 knots at 3700 RPM. He's 100 RPM short of max RPM, but 10 knots plus short of max speed. I make that under propped.
DavidJ
Well-known member
Do you know the boat history?
I don’t suppose the legs have been pranged and someone has got hold of a couple of legs from a different type of boat where the internal gearing is different.
I know this is something that folks look out for when replacing internals with used parts.
Just a random thought!
or re-engined but the drive ratio wasn’t changed
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stelican
Well-known member
If so it should be red lining
PaulRainbow
Well-known member
It's 100 RPM short of max Rpm and we don't even know if the OP is holding it full throttle.
How do you explain 100 RPM short of WOT but over 10 knots short of max speed ?
stelican
Well-known member
Barnacles on the props maybe. Thought max revs 3900.
Start with the easiest things first.
PaulRainbow
Well-known member
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stelican
Well-known member
Are you sure.
PaulRainbow
Well-known member
Why are you still arguing ?
stelican
Well-known member
Don't be silly I am not arguing, Just speaking from experience however I do now see that Volvo quote 3800.
Could you also advise max revs KAD32
not WOT
PaulRainbow
Well-known member
32P is 3800 RPM
DavidJ
Well-known member
That’s interesting. My experience of barnacled props is a dramatic loss of speed coupled with a non achievement of max rpm and seeing maybe 3000 rpm or less on full throttle, way below any WOT specs
The op seems to be experiencing something quite different.
stelican
Well-known member
Is that sumlog or GPS speed?
QBhoy
Well-known member
Also keen to ask if that’s a gps speed or paddle wheel reading. I’d also say that either way…a genuine 40 knots gps would be an ambitious pace perhaps.
I’m sure you’ll know already…but trimming up and making sure the trim tabs are up and clear help too. As you’ll know.
Turbo health and all that won’t need mentioned either no doubt. But given the props are as they should be and all else healthy…if you’re at 3700 (think their max range is around 3700-3900 maybe)…, you’re not going to make up 10 knots or so, with an extra 100 rpm, I’d say. Might assume that one of the numbers of the equation, isn’t accurate perhaps.
I’m sure you’ll know already…but trimming up and making sure the trim tabs are up and clear help too. As you’ll know.
Turbo health and all that won’t need mentioned either no doubt. But given the props are as they should be and all else healthy…if you’re at 3700 (think their max range is around 3700-3900 maybe)…, you’re not going to make up 10 knots or so, with an extra 100 rpm, I’d say. Might assume that one of the numbers of the equation, isn’t accurate perhaps.
stelican
Well-known member
This is also running on the Fajine owners site.
PowerYachtBlog
Well-known member
Few little dings even if you have the correct props can affect performance by not little.
About re-pitching I would also be balancing, which takes another 2 knots, and then you have to trim after say 28/30 knots 3400 rpm.
I sea trialled a Targa 40 with same engines touching 40.7 knots in the Med sea, which is denser and saltier to British sea and at 27 degrees.
I also touched 37 knots on a Targa 40 with the same 5 adults and a child, 20% fuel, and C4 propellers.
Harpergreg
New member
Hi yes, it seems paddle speed on tri data is miles off.assumed when they fitted new axiom and this together, beginning of the season it was bang on.
It seems that was showing 28 knots
And when checking my phone all the same time, I was 39 knots.
stelican
Well-known member
Has anyone shown you how to trim boat for max speed?
Harpergreg
New member
Yes all good with that thanks