Standard Propeller size for Antares 620

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robeverton

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I recently purchased a 2003 Antares 620, Nanni 5.250 with Technodrive 345A. Great little boat and very happy with it.
However the previous owner, for whatever reason, replaced the prop in 2016 with a 18" x 17" RH 4 blade.
The boat currently has a reasonably clean bottom and has been copper coated.
The engine revs easily to 2900 when not under load.
When under way and at full throttle it will only reach 2400 rpm and the boat will not go above 12 knts.
I suspect it is over-propped, maybe the previous owner needed torque/power rather than speed.
I would like to change the prop and have tried to find out the spec of the original standard three blade prop.
I've sent numerous emails to Beneteau agents/Peachments etc and had no response.
Can anyone on the forum help me with this info? Or even come up with any other reasons/solutions.
Many thanks in anticipation.
 
Jamie, Thanks very much for your comments. I have already got the general spec sheet but apreciate your effort.
However ..... earlier today I heard from Beneteau who assure me the standard prop was a 19 x 18 3 blade.
On talking to Michigan Wheel who supplied the present 4 blade in 2016, they maintain that it should still reach 2800 rpm and give 16.5 knots.
I think maybe I need to look at something else being the culprit.
 
robeverton said:
I recently purchased a 2003 Antares 620, Nanni 5.250 with Technodrive 345A. Great little boat and very happy with it.
However the previous owner, for whatever reason, replaced the prop in 2016 with a 18" x 17" RH 4 blade.
The boat currently has a reasonably clean bottom and has been copper coated.
The engine revs easily to 2900 when not under load.
When under way and at full throttle it will only reach 2400 rpm and the boat will not go above 12 knts.
I suspect it is over-propped, maybe the previous owner needed torque/power rather than speed.
I would like to change the prop and have tried to find out the spec of the original standard three blade prop.
I've sent numerous emails to Beneteau agents/Peachments etc and had no response.
Can anyone on the forum help me with this info? Or even come up with any other reasons/solutions.
Many thanks in anticipation.
Click to expand...
You could try finding another 620 out of the water with same engine with the original prop (try searching ones for sale?) and measure the pitch MANUAL PROCEDURE FOR PROPELLER PITCH MEASUREMENT and diameter.

www.solocoastalsailing.co.uk
 
The trouble in this neck of the woods is it’s near impossible to try out different props, unlike Stateside where they have prop parties. Looking at the specs it’s pretty finely balanced, 300rpm give you the extra 6 knots wot with the original prop, wouldn’t take much to upset that balance. As Chrome Dome says, extras like an aux engine etc could tip the balance.
 
Many thanks for all of your comments and advice.
Although I have mentioned that the bottom is reasonably clean and copper coated, there may be more growth on it than I thought.
I suppose its possible barnacle attachment on prop/skeg/rudder is causing this.
Boat is on a mud drying out mooring in Devon and although it looks clean from the shore maybe I am expecting too much.
Time to get it on the slipway and have a clean up before radical changes.
 
robeverton said:
I recently purchased a 2003 Antares 620, Nanni 5.250 with Technodrive 345A. Great little boat and very happy with it.
However the previous owner, for whatever reason, replaced the prop in 2016 with a 18" x 17" RH 4 blade.
The boat currently has a reasonably clean bottom and has been copper coated.
The engine revs easily to 2900 when not under load.
When under way and at full throttle it will only reach 2400 rpm and the boat will not go above 12 knts.
I suspect it is over-propped, maybe the previous owner needed torque/power rather than speed.
I would like to change the prop and have tried to find out the spec of the original standard three blade prop.
I've sent numerous emails to Beneteau agents/Peachments etc and had no response.
Can anyone on the forum help me with this info? Or even come up with any other reasons/solutions.
Many thanks in anticipation.
Click to expand...
There is nothing quite like a previous one ow er??
 
You could have a word with someone like Steel Development to see whether the current prop could be repitched. A couple of inches off the pitch would give you 2800rpm if it’s possible to go two inches.
 
I have been looking for propeller size for the Antares 620 or the Jeanneau MF635 that has the same hull. I have the original propeller but have installed a bigger engine. 50hk to 75hk. My propeller is 19x17 now and it is too small. My gearbox is 2.71-1 and max rpm engine 3000rpm. I can see from the ones having the Nanni 85hk are doing 16.5kn but I do only 11kn with mine now at full throttle. I sent mails to Jeanneau but they sent me to the Norwegian site and they never reply. I have contacted propeller supplier and they calculated 19x25 which I believe is far to large. I don’t want to spend the money for a new propeller before I have more information. So if some one can give following from their Antares 620 or MF635 it would be greatly appreciated

Engine size and type
Gearbox ratio
Propeller size in inches (dia and pitch)
Speed at
1000 rpm
1500 rpm
2000 rpm
2500 rpm
3000 rpm
Full speed

My speed with the VP D-75 (Gearbox 2.71x1)
1000 4.3knop
1500 5.6
2000 6.7
2500 7.7
3000 10.4
3150 11

My speed with the VP MD22 (Gearbox 2.71x1)

1000 rpm 4.3kn
1500 5.6
2000 6.7
2500 7.5
2750 8.5
 
What a nice bunch of data :)

The only bit missing is the normal total weight including all stuff, gear, fuel, staff etc. which has a lot of impact on the speed. If you can, remove some dead weight at it will improve speed and consumption - for free!

For inspiration and guidance try one (or more for comparison) of the online propeller calculators - e. g. Vicprop - Prop calculator for Displacement and semi-displacement hulls.

If estimating 3500 pounds (1600 kg) total weight and entering factory boat dimensions (say Hull draft in feet (excluding keel) = 1 ft or 30 cm) it returns 12.81 knots as the max speed 75 horses will be able push, suggesting prop sizes:

06-08-2022 06-57-18.jpg
 
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The weight of the boat is higher due to some additional equipment but it should not slow down the boat by so many knots.
I have tried the calculators and also the calculations from propeller suppliers but I believe they will give me a to large propeller 19x25.
Also my max rpm was 3150 but the engine is 3000max.
I have measured the boost pressure and on full it reaches 0.6bar, but according to the performance curve this pressure should be reached at a much lower rpm and kept at 0.6 bar until full by adjustment of the turbo exhaust bypass.

I just hope someone can tell me their propeller size with the 85hk or another engine but I will need to know the gearbox ratio so I know the propeller speed and can calculate the speed. I know the slip will be very high due to the hull shape.

I have checked the propeller speed with a tachometer so I am sure my gearbox is 2.71 to 1.

So as you can see from my figures my engine is running too light due to the propeller being too small.
 
How fast does the engine go warmed in N , You say 2900 rpm ?
They are over propped if they can’t match that in F . Your 2400 rpm

Manufactures tend to sign off the rpm a prop can achieve about 3 % over WOT .This gives a bit of wiggle room for seasonal fouling and cruising stores etc .

If you go mad with weight gain ( Chrome domes point ) then it’s customary to shave pitch off to meet the 3 % over rpm at WOT .
Always go the other way .

Once over propped its putting excess strain on the motors through out the rev range .Plenty of info on line about this effect.
Peeps erroneously think it’s will ( in this case ) be ok under 2400 rpm ie running @ say2200 rpm it’d still overloaded and the EGTs are soaring .
Its not a zero sum game a binary thing the prolonged excess cylinder temps mushroom the exhaust valves they don’t seal as well and you loose Hp . Risk head gasket damage etc etc .
 
Google found

Bought a 2003 Merry Fisher 635 last year. Has an 85hp Nanni 5-250tdi engine, twin disc gearbox with
2:1 reduction ratio, 16" * 14" prop.

I love the boat, but can only get 10knots at WOT (2800rpm) Everyone tells me I should be getting at least 16knots

engine is in great condition (650 hours). Prop is new and only slightly bigger than manufacturers recommended (15"*13")
recent haul-out with bottom antifouled and is clean as a whistle. only me in the boat and everything cleared out (tools/oils etc)
 
I have already seen this post and his propeller is too small. He should increase the diameter (19” seems the largest that can fit) for better efficiency of the propeller. The pitch is what I would like to know was original on the boat with the 85hk and 2x1 gearbox. The 14” is way to small but should give a theoretical speed of 16.1kn, but due to the propeller efficiency and shape of the hull he is only getting 10kn. This is about the same as I get with mine which should have a theoretical speed of 15.45kn (@3000rpm Volvo Penta D2-75) 19x17” propeller.

still I hope someone reads this post and can tell us more about the original propeller with the other engine alternatives that were installed.

The post that says manufactures recommended size to be15x13” is wrong for these engines and would have been for a even smaller engine then the 50hk that I previously had installed with the 19x17” propeller and this was the original.
 
Thanks for all your comments.
Since my first post I have carried out the following
1. Replaced turbo, exhaust manifold, waste gate actuator, Exhaust mixer elbow. (Huge amount of corrosion on existing manifold and mixer)
2. Primary fuel filter and secondary filter, cleaned and checked fuel lines.
3. Just had copper coated hull cleaned
I can still only get 13.5 Kn max at 2500 rpm.
Very little weight on boat apart from 100l fuel, me 15 Stone (Honestly!) and a few fishing rods etc.
Engine will rev to 3000 in neutral with no smoke.
I have a couple of questions if any one can help.
A. Should I change the prop ?- (Currently 18 x 17 RH 4 blade. Standard fitted prop on the 620 Antares is a 19 x 18 3 blade)
B. How do I set the waste gate actuator adjustment on the threaded connector? (Currently set at 3 turns)
(2003 Antares 620, Nanni 5.250 tdi 85hp, 2:1 Techno gearbox)
Any advice appreciated.
 
robeverton said:
Thanks for all your comments.
Since my first post I have carried out the following
1. Replaced turbo, exhaust manifold, waste gate actuator, Exhaust mixer elbow. (Huge amount of corrosion on existing manifold and mixer)
2. Primary fuel filter and secondary filter, cleaned and checked fuel lines.
3. Just had copper coated hull cleaned
I can still only get 13.5 Kn max at 2500 rpm.
Very little weight on boat apart from 100l fuel, me 15 Stone (Honestly!) and a few fishing rods etc.
Engine will rev to 3000 in neutral with no smoke.
I have a couple of questions if any one can help.
A. Should I change the prop ?- (Currently 18 x 17 RH 4 blade. Standard fitted prop on the 620 Antares is a 19 x 18 3 blade)
B. How do I set the waste gate actuator adjustment on the threaded connector? (Currently set at 3 turns)
(2003 Antares 620, Nanni 5.250 tdi 85hp, 2:1 Techno gearbox)
Any advice appreciated.
Click to expand...
A. No you first need to get max rpm on the engine. Have you checked injectors and fuel pump? Also checking the compression on the cylinders if you take out the injectors. Since you have a smaller propeller then the original you should have no issues getting the max engine rpm or even more.
B. Fit a pressure gauge on the hose (if there is a hose) from the turbocharger compressor side (air side) with a t-piece to the waste gate. In the specification of the engine it should be a “boost pressure” figure for different loads. This pressure can be checked but it will not tell you if you are getting exactly full load on the engine but it is a reference and will tell you how hard the engine works.(Boost pressure at 2800 rpm : 0.54b to 0.56 bar). I am not sure at what load on the engine the wate gate starts to open and then the boost pressure will not increase, but if you are now getting this pressure your engine is running at full load even at only 2500rpm and it is overloaded according to the propeller curve.
Thanks for getting the original propeller pitch and I can do some calculations for my own installation on a MF635. I have installed a VP D2-75 engine and working on the propeller. We installed a19 x 25 x 3 and the gearbox is 2.71:1 and 3000rpm. This was the vendor calculation but when we tried we only got 2450rpm. Now we have sent it for adjustmentbut have not yet been able to test it yet.
 
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