GPS Measured speeds on 330SS w/ 375hp 496 Mags


kai330

kai330

Member
Here's some GPS speeds. On board, we had full fuel, first mate and I and our long weekend load of clothing, food, etc.

RPM Speed in MPH
3000 33
3200 35
3400 40
3600 42
3800 45
4000 48
4200 50
4400 53
4600 56
4800 58

Top Speed 60.0

Top speed was obtained later as we burned gas down and got lighter. I had to really work it, but we got an honest GPS measured 60.0 out of the boat.

Fuel Burn
We ran almost two hours and varying speeds with about half at 3400ish and the other half trying different RPMs and trims.

We burned just over 75 gallons doing it and I was pretty happy with that.
 
Man that is awesome...I have the drive train setup and I top out at 50 MPH on GPS, so your numbers make total sense. Man you have a great cruising speed at 3400 RPM's.

Enjoy !
 
toofast said:
Man that is awesome...I have the drive train setup and I top out at 50 MPH on GPS, so your numbers make total sense. Man you have a great cruising speed at 3400 RPM's.

Enjoy !
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Thanks toofast,

We have a GPS on an iPad and we're experimenting with speeds and such. We're doing a few hours at a steady 3300 RPM to get a feel of fuel burn since we don't have any fuel flow meters onboard.

You're nor doing too bad yourself; you have a lot more boat to push around and the same power.

Heading out for another few hours of experimenting now to see what happens.
 
Longhorn said:
Very interesting ... are you using any specific app to to record the data?
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We downloaded a cheap iPad app (SeaNavUS) that has all US charts on it and we also gives speed. We also double checked speeds on a free GPS app (Speedpro+) that gives MPH info.

We just ran the boat three hours to check fuel burn. We idled out of the marina and got to a 3300 rpm cruise which gave us a GPS average speed of 38mph. We had run the boat 3.2 hours when we fueled which was all at 3300 rpm other than maybe 20 or 25 minutes of idling in and out. We took on 64 gallons for about 20 gph average.
 
330_SS said:
How optimistic is the speedometer - how much faster does it read than the confirmed GPS speeds?
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Actually, the speedo pickup is not working so it shows dead in the water. Another thing to fix......
 
kai330 said:
330_SS said:
How optimistic is the speedometer - how much faster does it read than the confirmed GPS speeds?
Click to expand...


Actually, the speedo pickup is not working so it shows dead in the water. Another thing to fix......
Click to expand...

Yeah, mine goes bad a ton as well...most likely you have a bit of gunk / junk / whatever in the little hole in the outdrive that feeds the water pickup tube. If you have a mask, you can stick a piece of wire and fish it around, trying to clear it.
 
toofast said:
kai330 said:
330_SS said:
How optimistic is the speedometer - how much faster does it read than the confirmed GPS speeds?
Click to expand...


Actually, the speedo pickup is not working so it shows dead in the water. Another thing to fix......
Click to expand...

Yeah, mine goes bad a ton as well...most likely you have a bit of gunk / junk / whatever in the little hole in the outdrive that feeds the water pickup tube. If you have a mask, you can stick a piece of wire and fish it around, trying to clear it.
Click to expand...


Mask! I have full scuba gear! Another excuse to go scuba diving, woo-hooo!
 
Anyone that has a pitot tube speedometer that works properly, raise your hand (lol). I had one on a go fast boat, never worked correctly. I think that's why they invented GPS based speedometers ;D.
 
Numbers are very close to Kia330. Same pitch props with 2.0:1 ratio B3's. Across the board, same load and rpm's, I am about 2 mph faster with a top speed with fuel under a half tank and only a couple people on-board is just over 62mph. But hardly ever run that fast.

Fuel consumption: Done the old fashion way. Full tank- reset trip odometer-run a 100 miles or so-top fuel back off and calculate. MY average is 1.37 mpg. (statute). My best was a trip 2 years ago from home to Chestertown, MD. Chester River and back at 3100 rpm and never went faster. I got 1.51mpg. The worst was this past July 4th from home to Solomons Island hitting a head-on sea of 2-3's south of the bay bridge to 3-4's of Calvert Cliffs and the Fuel Pier. Just before the turn to the Patuxent River, We hit a couple sets of short interval 5 footer's and dipped the bow twice. Average running speed started at 33 mph in the Magothy, Low 20's south of the bridge. (actually probably high teens) Then down to 12 mph for the last 2 hours. Filled up the next morning before going to Vera's and only got 1.08 mpg. Running time should of been 2h 15 mins but ended up 4.5 hours.
 

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Thanks for the input Hermyclaus.

Thus far, I've been very pleased with the fuel burn on our boat. I had anticipated an average of 25-30 GPH based on how we usually ran our Baja 236. Thus far we're averaging around 21 or so. I don't know what that figures for a MPG measurement, but I am pleased with it.
 
330_SS said:
How optimistic is the speedometer - how much faster does it read than the confirmed GPS speeds?
Click to expand...


We cheated. We just added a Faria GPS 0-60mph speedometer over the winter. Drop in replacement for the stock speedo and does not need an external antenna.

Damn slick and accurate. What more can a guy ask for?
 
Just finished running in Door County, WI with the same set-up. My speedo shows faster than the GPS. Showing 60 when at 58. That was best we did with full load of fuel, water and first mate. Also fresh BottomKote NT on the hull. Going to try to tweak a little more on the drives and trim tabs.
 
kai330 said:
We cheated. We just added a Faria GPS 0-60mph speedometer over the winter. Drop in replacement for the stock speedo and does not need an external antenna.

Damn slick and accurate. What more can a guy ask for?
Click to expand...

Do you happen to have the model/part number you purchased....I need to make this change.

Thanks,
 
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