JoAna
Member
I just want to know what diameter prop and pitch is the most popular in use today.
420 sedan bridge 2005 Cummins 6CTA
- Thread starter JoAna
- Start date
Pura Vida dos
Member
- Oct 23, 2017
- 76
- Boat Info
- 2005 420 Sedan Bridge, Highfield 340 on Freedom Lift, Garmin 7612
- Engines
- Cummins 480CE
Mine came from the factory with 26 x 26 props. I had them re-worked last year. Changed them to 26 x 25 to get fuel burn numbers more inline. Got close but still not quite there, Next time I have them off will probably change to 26 x 24.5
JoAna
Member
Thanks ours arecurrently 26 x 23 fuel burn @ 2350 RPM is 35 gph and running at 21knots. FYI
ZZ13
Well-Known Member
Your fuel burn is right on the 6CTA curve, so looks like you are propped nicely for your load. Do you cruise at 2350? I stay 2100-2200.
JoAna
Member
My 2150 RPM burn rate is 28GPH @ 16.5knots. My total travel distance on one tank of fuel is the same. I just get there faster.
At 1200 RPM burns 7gph speed is 9.5knots. FYI my fuel/water tanks are at 50% with fully loaded boat.
At 1200 RPM burns 7gph speed is 9.5knots. FYI my fuel/water tanks are at 50% with fully loaded boat.
Tomco
Active Member
- Aug 16, 2012
- 455
- Boat Info
- 2004 420 Sedan Bridge
GHS Hydraulic Lift
11' Walker Bay, 30hp
- Engines
- Cummins 6CTA 8.3M
So how did you determine fuel burn (GPH) with mechanical engines? Having ours for only a few weeks before winter layup I don't know all the systems but I didn't think it was possible without adding fuel flow sensors ...
Tomco
Active Member
- Aug 16, 2012
- 455
- Boat Info
- 2004 420 Sedan Bridge
GHS Hydraulic Lift
11' Walker Bay, 30hp
- Engines
- Cummins 6CTA 8.3M
My props are 26x23 ... have some tach issues to resolve before being able to accurately determine WOT RPM.
JoAna
Member
I have mechanical fuel flow scans
Alex F
Well-Known Member
- Nov 14, 2006
- 9,166
- Boat Info
- 2005 420DB with AB 11 DLX Tender, Raymarine Electronics (2x12" MFDs) with Vesper AIS
- Engines
- Cummins 450Cs, 9KW Onan Generator, 40HP Yamaha for tender.
I'm swinging 23D x 26P.
Based on my observation, 480CEs usually swing larger diameter props (in a 24" to 26" range). Anytime I hear owners say they swing stuck 26 x 26, I roll my eye in disbelieve on how SR could imagine that just 30 extra HP will swing these props at rated to 450 specs RPMs. Perhaps that's why we hear more dropped valve stories from 480CE owners having overloaded engines. Obviously, swinging 23s on 450s we lose about 2 knots in comparison to 480s with 26s. But, I'm perfectly fine with it knowing that my engines are happy.
Based on my observation, 480CEs usually swing larger diameter props (in a 24" to 26" range). Anytime I hear owners say they swing stuck 26 x 26, I roll my eye in disbelieve on how SR could imagine that just 30 extra HP will swing these props at rated to 450 specs RPMs. Perhaps that's why we hear more dropped valve stories from 480CE owners having overloaded engines. Obviously, swinging 23s on 450s we lose about 2 knots in comparison to 480s with 26s. But, I'm perfectly fine with it knowing that my engines are happy.
JoAna
Member
That's right where I'm at. I like the prop load. The way I tested the boat was 25% fuel capacity, 25% water capacity, very little provisions, and 4 fat guys. The boat ran to 2735 RPM's which I'm told is acceptable for prop test load only. Then, after I bought the boat I serviced the cooling system, I loaded it down with 100% fuel capacity, 100% water capacity, provisions for 5 days of travel and two adults and ran the boat 100% wide open and the RPM's ran to 2635. So I know the boat is propped properly for loaded conditions. 2600 RPM's is the recommended maximum range - I usually run the boat at 2350 for the duration of most trips I'm on.
Last edited:
Alex F
Well-Known Member
- Nov 14, 2006
- 9,166
- Boat Info
- 2005 420DB with AB 11 DLX Tender, Raymarine Electronics (2x12" MFDs) with Vesper AIS
- Engines
- Cummins 450Cs, 9KW Onan Generator, 40HP Yamaha for tender.
Minor correction on my props. When I purchased the boat it had super heavy cup (0.11). There's a bulletin stating that 450s spec is actually 2700RPMs. When I saw that I was making only touch above 2600, I reduced the cup by 1/2 and that gave me around 50-75RPMs extra.
Point being:
1. 2700RPMs is the accurate spec for 450s. Later on the same recommendation was issued for 480s. See if you can access this link: https://documentcloud.adobe.com/link/track?uri=urn:aaid:scds:US:3574634c-12d2-400c-b61c-d28e2fda7b3e
2. Know the size of your cup as it plays a big role during the tuning process.
Point being:
1. 2700RPMs is the accurate spec for 450s. Later on the same recommendation was issued for 480s. See if you can access this link: https://documentcloud.adobe.com/link/track?uri=urn:aaid:scds:US:3574634c-12d2-400c-b61c-d28e2fda7b3e
2. Know the size of your cup as it plays a big role during the tuning process.
manfredr
Member
I have a 2004 420 SB bought new. I have the 26x23 as well. Had some cupping reduced years ago, because I could barely react 2600 rpm. I also cruise mostly at 2350 which gives me roughly 20 -21 knots depending on the tide.
