Nanni 4.390 saga continues (low power low speed)

mind there is a bulky shaft anode just ahead of the p-bracket. In theory you don't need both!
I used to have shaft anodes for the last 5yrs, now switched to propnut anodes and will see how it goes. Since I'm lifting out every two years, I thought that propnut ones are easier to replace in the water. Stupid thought as I need arms of a monkey to reach them with my head out of the water... Still easier for the diver to change since there's only one hex nut there...
BTW, your shaft anode is slightly too close to the bracket, water needs to be able to flow and cool the cutless bearing there. Not to mention that when it wears, it looses it's athesion from the shaft and ends up stuck on the p-bracket disrupting water flow.

V.
 
vas said:
mind there is a bulky shaft anode just ahead of the p-bracket. In theory you don't need both!
I used to have shaft anodes for the last 5yrs, now switched to propnut anodes and will see how it goes. Since I'm lifting out every two years, I thought that propnut ones are easier to replace in the water. Stupid thought as I need arms of a monkey to reach them with my head out of the water... Still easier for the diver to change since there's only one hex nut there...
BTW, your shaft anode is slightly too close to the bracket, water needs to be able to flow and cool the cutless bearing there. Not to mention that when it wears, it looses it's athesion from the shaft and ends up stuck on the p-bracket disrupting water flow.

V.
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Good info thanks. Yes shaft anode done last year but not prop anode. Was suggested one goes on rudder too. Not much I can do about the spacing as it's back in the water.
 
Hi Freddy. I just checked the pictures on my phone of my prop and it’s 21*23.5. I don’t know if mines correct or not however but that’s worth investigating.
 
Thanks I will be looking at prop options. Others have talked about trim tabs as she does sit bow up when on the plane but these are expensive. Appreciate all the feedback and will be reporting back on results. Nothing I can do about the anode being incorrectly fitted for a while but it's noted.
 
before you start spending money on props, yours is 21X22, so shorter than the one paradave has 21X23.5. If you go that way (increasing pitch) you're going to be worse off!
check what you get with clean hull and prop, then check what gear ratio and engine you've got compare to fe paradave and then you can start thinking going "lighter".
Doubt you'll need to do so btw!
Trim tabs may be useful although I vaguely remember someone here mentioning that it made no difference whatsoever in his

V.
 
I was wanting understand the propeller function rather than change it. I am not clued up on the subject. I am happy if the boat is performing as it should and is fully tuned after being tweaked to get the optional power available via engine/turbo. I am just concerned I am at full chat to stay on the plane which must be using a lot of fuel. We will have some results today on maximum performance with clean hull and prop.
 
paradave said:
Hi Freddy. I just checked the pictures on my phone of my prop and it’s 21*23.5. I don’t know if mines correct or not however but that’s worth investigating.
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Same size as mine, we have the same engines so gearbox ration on the Nanni may be slightly different.
 
Problem solved! She pulled 3600 revs and was pushing 20kts but I had some vibration through the rudder at WOT so I backed off to 3400. Much easier to get on the plane and cruise at 17kts if required but happy at 16+kts 3200 revs. The sea was not as flat as Friday so this would knock a little off performance. So barnacles were the problem. I am still not sure how old they are but clearly I have gained 200 revs and 3kts.
The steering vibration may be the prop slightly out of balance?
She does seem to be bow up on the plane so some foils may get her level and quicker although expensive.
I will do the work suggested on turbo just to be sure.
Thanks for all the input. I am going to get a waterproof camera and monitor the growth without hauling out every 3 months.
 

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well done, tbh was expecting this result...
btw did you check cutless bearing for play when she was out?
Now, since most likely turbo will also be fine, do your man maths right and get some trim tabs with the money you were prepared to spend fixing what didn't need fixing :p
enjoy the summer

V.
 
Excellent. Glad it’s sorted. I’m interested to hear how you get on with the trim tabs. They’re a very bow up boat and can see the tabs really helping get over the hump earlier.
 
Brilliant. Glad you are sorted. Also, found the pic of my prob. Exact same as yours.
 
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I’ve got a nanni 4.380 and my maximum revs are suddenly 2900 making speed 12knots instead of 3600 and up to 20knts - I’ve done all the checks recommended on this thread but nothing is solving the problem. I’ve booked in for lift out but am doubtful that light fouling I can observe at low tide (drying harbour) would cause such a massive drop in performance. Any ideas?
 
James066 said:
I’ve got a nanni 4.380 and my maximum revs are suddenly 2900 making speed 12knots instead of 3600 and up to 20knts - I’ve done all the checks recommended on this thread but nothing is solving the problem. I’ve booked in for lift out but am doubtful that light fouling I can observe at low tide (drying harbour) would cause such a massive drop in performance. Any ideas?
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Check that the control is actually opening the throttle fully at the pump.
Dirty fuel filter.
Crap around the prop/driveshaft, try a shot of reverse.
 
T
chamac said:
Check that the control is actually opening the throttle fully at the pump.
Dirty fuel filter.
Crap around the prop/driveshaft, try a shot of reverse.
Click to expand...
Thanks
Yeah the control goes all the way, fuel filters have been changed, prop not fouled, no vibration or weird noises starts fine runs normal but just not past 2900rpm
 
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