480 DB Owners Club

1950 RPM will show about 28.5-29 MPH. Will burn 41-42 GPH total.

I noticed the boat test noted prop size was 28x33. I have 28x31 and thought this was a standard prop for all 480's. Did the cat boats come with different prop pitch? This could account for the slight additional MPH but load would be the concern.

Running at 1950 RPM the load shown on the ED display is about 73%.

I can reach WOT full fuel and water, clean bottom. I think I have the correct prop's.
 
I'm swinging 28x32's and my load is about 70-71% at 1950. I generally run around with half fuel and very little water unless going on a long trip though.

Not sure if you guys are on Boatdiesel, but Tony Athens is adamant about not putting more than 18 GPH through a QSM11 at cruise and making sure they can turn up 2350-2360 at WOT. He believes that this is the leading cause of the exhaust manifold leaks that so many of them exhibit.

I can reach 2320-2330 with a clean bottom so I may have my props tweaked this winter for a little more RPM.


Sent from my iPad using Tapatalk HD
 
Been on boat diesel for a long time, but recently let my subscription lapse. Have to join in again as that site is a great resource. Interesting that Tony mentions 18PGPH as a max throughput. This would bring cruise RPM at about 1800. Given the standard 80% rule for diesels, this cruise rpm would contradict the rule. Cruise should be closer to 1900 RPM. Close, but when you factor in boat loading, bottom conditions...etc. this may make sense. I find the 1950 cruise RPM to work best for me but I am running more than the 18GPH. I think most of us with the Cummins cruise in a range a little higher.
 
I agree that 18 GPH cruise would be too slow for my liking so I'm going for a happy medium.

Im not sure what RPM it would take to get me to 80% load but its not within my comfortable cruise range. I'm usually between 68-72%.
 
I very seldom run higher than 80% load on my MANs it's not necessary . 1850 RPM normally sets me right around 70-75% load and that's if I'm in a hurry , we really like about 1100 RPM , Slow and Low .


Boltman
 
I noticed the boat test noted prop size was 28x33. I have 28x31 and thought this was a standard prop for all 480's. Did the cat boats come with different prop pitch? This could account for the slight additional MPH but load would be the concern.
Click to expand...


My spare props are outside in my shop. If I go out later today, I will see if I can read the pitch on them. I know they are 28's.

Also Max load at WOT @2300rpm. is 93% and 94% on the 3196's. (actually I think a pinch over 2300) Full fuel and water. (and family and dog and food and beer and, and, and) The longest I have stayed at WOT was a few times at 3-4 minutes tops. I cruise around 1750rpm 60-65% load, but keep in mind we just bought the boat the end of summer and haven't had time to tweak things out.

Of course TURKEY is my first priority today. :grin:
 
I did a fair bit of research prior to having my spare props repitched. In the end, I did three models (light boat, average and heavy boat) using the best prop calculator I have ever seen from these folks:

http://www.vicprop.com/calculator.htm

I then took my results into their shop for discussion before having them do the repitch.
 
Did you end up repitching? If so, where did / will you end up?

I used the prop calc and it was pretty close. One variable I don't understand is the hull constant. Based on their chart, the hull constant on average cruisers is 150. When I use this number with all of the other variables on the vessel, and a desired top speed of 29.5 knots, it says to use a 28x27.4 - 4 blade prop but they base the calculation on a top speed of only 24.5 knots stating the required HP at the prop is 1700 and there is only 1176 available. I then decided to mess with the hull constant leaving all other data the same. When I get to a 175 hull constant. It is exactly the way my props are configured and the performance numbers match up pretty good. It still says a max speed of 28.6 knots is what they based the calc on due the the HP availability.

I recently had the props checked / repitched and scanned. 28x31.1 was the result. At WOT 2350 RPM, get exactly 29.5 knots. Half fuel, half water, clean bottom.

The hull constant seems to make a significant difference in their calculation. Wonder if Vicprop could elaborate on where that calculation is derived from. Also, how does cupping affect the numbers? (a thread discussed previously)
 
boltman said:
And what was your result , but truly come on who watches all this crap while under way I just have fun!!


Boltman
Click to expand...

Boltman; Perhaps you don't understand; you can't have fun unless your props are done correctly. And considering the cost of repitching props or worse still, overloading your engines, it is worth the time to do a thorough job.

Unfortunately, the subject involves some complexity. Class dismissed.

Yzfspike: I had the props done at Vic Prop, the folks with the prop calculator being discussed. Went with the hull constant of 150. Remember, our boat is 6V92TA (non DDEC) Detroits.

Here is the Calculator Output:

VicProp Calculated – Std Specs - Light Boat


The following calculations were done using a calculator provided by the Victoria Propeller website:
http://www.vicprop.com/calculator.htm


Waterline length in feet: 41 feet (estimated)
Beam at the waterline in feet: 14 feet (estimated)
Hull draft in feet (excluding keel): 3.75 feet
Vessel weight in pounds: 41000 lbs
Engine Horsepower: 535 HP
Number of engines: 2
Total Engine Horsepower: 1070 HP
Engine R.P.M. (max): 2300 RPM
Gear Ratio: 1.73:1
Shaft R.P.M. (max): 1329 RPM
Number of shaft bearings (per shaft): 1
Hull Constant: 150
Desired speed in Knots: 25 knots
Horsepower Calculations
This will calculate the maximum horsepower and torque available at the prop(s).
Total available horsepower at the engine(s): 1070 HP
Total available torque ft/lbs at the engine(s): 2443 ft/lbs
Horsepower loss of 3% per gearbox: - 32.1 HP
Horsepower loss of 1.5% per shaft bearing: - 16.1 HP
Total horsepower available at the propeller(s): 1021.9 HP
Total torque ft/lbs available at the propeller(s): 4037 ft/lbs
Speed & Power Calculations
Calculations based on desired speed and available HP
HP required at propeller(s) for desired 25 knots speed: 1138.9 HP
Estimated speed with existing 1070 horsepower:
This is the speed we will use for the propeller size. 23.68 Knots
At this point it is important to note that all of the calculations above are based on full RPM and HP. Most engines are rated to run at a percentage of thier full RPM. This is what will determine your maximum cruising speed. The propeller sizing calculations below are based on 90% of full RPM, which allows the engine to develop it's maximum
power without overloading. The chart below shows typical engine ratings, you can find this information in your engine specifications.
Recomended RPM for continuous operation
Type of engine % of max RPM
Light-duty gasoline and diesel automotive conversions 70 - 80%
Light-duty or high output marine diesels 80 - 85%
Intermittent-duty marine diesels 88 - 92%
Continuous-duty heavy marine diesels 98 - 100%
Propeller Size
Number of blades Diameter (inches) Pitch (inches)
2 Blade 30.9 X 28.1
3 Blade 29.4 X 27.8
4 Blade 27.7 (28) X 27.2 (27)
Props on Just By Chance were re-pitched to 28x27 by VicProp in Nanaimo BC.
The propeller sizes shown above do not contain calculations for cavitation or blade loading.
If you find that the recommended propeller is too large to fit your vessel, you can try increasing the shaft speed. Failing this, you can reduce the diameter and increase the pitch at the expense of your propeller efficiency. The rule of thumb is 1 inch of diameter is equal to 1 1/2 to 2 inches of pitch.

The actual boat performance was pretty much as expected; full fuel otherwise light load yielded 24 knots at 2300 rpm.
Hope this helps.



 
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I'm sorry I guess I trust that my engines aren't being overloaded because they don't seem to work that hard but then again I have 400 more horsepower to work with , it shows too.


Boltman
 
Nice to have when you need it though!! I'll look at my spares in the lazzerette upon next visit to the boat. Just to see what I've got , I'd like to add another Turbo to each engine , but my Mans Man doesn't recommend it ... Like to crank these engines to 850hp just to keep her up on plane at a lower RPM , but these boat diesels are High output already so I really don't want to blow a motor ..... So I'll stick to a 1100 RPM cruise


Boltman
 
This probably belongs in the Electronics forum, but since we're all 480DB owners I thought I post it here first.

We just purchased a 2002 480 Sedan Bridge with 3196s. So far we're ecstatic with the purchase.

The electronics are all Raytheon from the year 2000 era. There's an RL80C, a ST7000+ autopilot, ST60 TriData, Ray220VHF, RN300 GPS (not necessary, but there), old Clarion stereos. My main focus will be the RL80C unit and any of the other devices the unit relies on. Unfortunately all the new units are in a landscape layout and the current opening doesn't seem to be able to accommodate any of the newer units.

My goal is to minimize any cutting of the helm or having to come up with filler pieces for the existing openings. I realize this may not be possible, but...

Has anyone replaced these units with newer and faster devices? What have you replaced them with and what were your experiences with the upgrades?

480SedBrgDash.jpg
 
I'm beginning to plan this project for next year. Luckily, I have an SR Navigator in the spot where your RL80 is so my dash cutout is much smaller. I don't think you will find any new style MFD's to fill that hole since they're all widescreen format now.

My plan is to install a Raymarine E125 there but the width will be very close to overhanging so I need to investigate that further or go with the narrower full-touch A125.

I assume you know that your radar scanner is not compatible with the newer units? My RL80's in the hardtop e-box so I'm hoping it hangs on for a few more years. When it goes, I will upgrade the scanner and install whatever A,C or E series that will fit. I know a 12" will not fit up there.
 
Yes, thanks for the reminder. I was told that it won't be a simple matter of replacing the head unit, but the scanner (radar) will also need to be replaced. Another option was to go a generation or two newer than the RL80C, but would still be compatible with the current analog scanner. I'll have to do some research as to what those models are and will post any developments.

This isn't an urgent task at the moment, just looking ahead a year or two. Purchasing the boat and slip rental, etc. etc. will have me counting my pennies for a while ;-)
 
There's a chart somewhere on Raymarine's website showing the analog radar serial #'s that are compatible with the E80, E120 etc... I tried that when upgrading electronics on my old boat (2001) but my radar was about 5 months too old so I had to bite the bullet and buy new everything.

IMO if you're spending the $$ I wouldn't upgrade to the Classic series since they're pretty old now and will be even older in a few years.
 
Quality Time... I just checked on the Raymarine site, my scanner is not compatible with anything but the old RL70s and RL80s. I'll start filling the piggy bank now and hopefully get another couple of years out of my old stuff.

Keep in touch and let me know when you're ready to start the upgrade process; I'd love to learn from your experiences.
 
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