top speed for a 2004 330 Express

[choogenboom]

I recently bought a 2004 330 Express with twin F225's. Best top speed I have seen is 37 MPH (GPS speed) with both engines running at 5700 RPM. Both GW and yamaha have published numbers saying I should see 41-42 MPH at 6100 RPM.

Here are the variables - let me know if I missed any

Boat is bottom painted, paint was immaculate on the day I speed tested.
15 1/2 x 17 polished stainless props, perfect condition (props have 17M stamped on them, thats the only marking)
engines mounted on the lowest hole
50% full fuel tanks
full Water tank
1 person
smooth water, water temp about 82F, air temp about 85F
460 hours on engines
E10 regular unleaded fuel

I am also unable to reproduce Yamaha's 1.53 MPG number or Grady's 1.2 MPG published number. With much fine tuning I can get to 1.1 MPG on my fuel meter. Yamaha's testing footnote says the data was collected using their fuel management system - how to they get to two decimal places when my guage only shows 1??

The fact that I am only getting 5700 RPM seems to indicate that I am overpropped? Or engine is not developing full power? Any other thoughts on possible causes? Other 330 Express owners with the F225s, what props are you running? Is your engine also mounted on the lowest hole? What top speeds are you seeing? What RPMs at top speed? Has anyone come close to the published numbers? Is this a symptom of using E10 gas?

 

[Daman858]

An organization that promotes the use of ethanol, the Ethanol Promotion and Information Council, states that you may loose 1 to 2% of your mileage on E10. Many report losses of 10 to 15%. Another outfit, the American Coalition for Ethanol, reports a 1.5% loss in mileage in tests they did on three separate vehicles. I noticed that my car mileage drops from about 31 to 28.5 MPG on E-10. It is a Honda.

So, the E-10, plus other variables may be the culprit.

 

[Tuna Man]

I would blame one or two mph and about a 200 rpm loss on smooth bottom paint. Do you have any antennas, radar, spotlight, outriggers, etc. that may add wind resistance? Were your curtains zipped up and running into a headwind? Did you remember to raise yout trim tabs and trim the engines all the way out until the rpms showed slippage, then lower the trim slightly on each motor? Are your engines well tuned? Is your fuel fresh? Are the lower units smooth or do they look like most (including mine after a long season) missing some paint in the skeg area? Is there a transducer that is in the water that may be contributing negatively? Is your boat as light as the one in the 'factory' test reports (different options, gear, tools, extra anchor or rode, ice, food and drinks, etc)?

I am not convinced that the same horsepower engine by any manufacturer of the same year is more than about one percent higher or lower in horsepower than another of the same model (ie: both your engines produced virtually the same hp when they were brand new). That being said, I have read many times that as long as the outboard produces within ten percent of what the sticker says, it is within guidelines. This includes all brands of outboards by the way.

I have done the performance tests on five Gradys so far, I owned three of them. On every one we could get almost exactly the same numbers as the Grady test. However, I must admit that we had to practically empty the boat to get the desired results. I think we all tend to forget just how much stuff we carry onboard that add to the weight (even life jackets weight something when you have ten onboard.

 

[ocnslr]

A few comments:

1. You indicate that the painted bottom was immaculate. But the GW and Yamaha tests are done with an unpainted bottom, and that alone is good for a couple of knots lost speed.

2. Your WOT RPM of 5700, compared to the test at 6100, has a three (3) MPH slower speed. http://www.go-fast.com/Prop_Slip_Calculator.htm

3. At your 5700RPM WOT, are you trimmed up properly? The usual approach is to trim the engines up, with both speed and RPM increasing, until the speed no longer increases, or you hear the props ventilating, and then trim down until the ventilating stops. I can say from experience that this is a critical process for preperly evaluating your prop and engine performance.

4. Ethanol has 30% less energy per unit, so an E-10 mixture would have 3% less energy overall. Small, but not insigificant.

5. Using the Prop Slip Calc above, your 37MPH at 5700 RPM gives a prop slip of 20% (gear ratio is 2.0:1). This is rather high, and indicates that something isn't right. Something possibly aerating the water ahead of the prop(s), such as a through-hull transducer mount, or water intakes, or ???.

Comments based on a good bit of experience with prop testing.

I'm sure some 330 owners will contribute their own experience.

Brian

 

[Tuna Man]

Just noticed the air temperature and the water temperature you were running in. I cannot tell where you live (or do your boating from your screen name), but I assume with these temps that you live down south? Is it also safe to assume that there was high humidity during your tests?

I think you will find that the boat perfoms better on cooler low humidity days. If I remember correctly most of the Grady tests are done during late fall or winter, maybe there is a reason for that....

I guess there are some advantages to living in the Northeast during the fall, we get to freeze our butts off and get .01mpg gallon better that you southern guys

 

[wahoo33417]

A Yamaha factroy guy (at a boat show) told me that a cold day vs. a hot day can mean a 10% horsepower difference to an outboard.

In consideration of factors that others have already posted, these 'real world' numbers don't seem so far off the 'ideal conditions' numbers posted by Grady and Yamaha.

 

[Fishtales]

I never believe such stats, they are for comparison purposes at best.

No curtains, no accessories with wind drag, no extra weight items, a perfectly calm sea, traveling with the current and wind, prior to E-10 or jacked fuel, and likely the people at the helm passed gas and used a bic lighter to get some extra zing.... All add up to an estimate of performance at best.

 

[NOTHING ELSE MATTERS]

I have the 250's instead of your 225's, on my 330 in the middle of summer(July) i got the full 6000 rpms and top speed of 42 one way 44 the reverse way(mph) as per GPS. This is with 2 people onboard(hefty ones),aprox 200 gallons fuel, full water, canvas up(closed), open array radar,antennas (2) for vhf, gps, search light, plus boat ready for fishing with all the gear and bottom paint. Also on my previous Bimini i was getting 48-49 mph, which is more than what they advertise. So i really don't know why yoy get that kind of speed but more important why you do not get the full rpms. Did you do a compression test when you bought the boat?

 

[choogenboom]

Thanks all for good feedback.

Bottom paint - I would say it was rough, like what you would find if it was done with a heavy nap roller, so if smooth == 200 RPM then the rough may account for most of my RPM

windage - all canvas was down for Hurricane Hanna. VHF antennas down, 24 ft outriggers in place, radar dome. So in the balance guessing that with the canvas down I had less windage than normal.

Tuna Man is right - I live in Beaufort SC and air is warm and humid. Warm wet air is less dense than cold dry air so engine has less power. As a sidenote, when I moved my 1994 GW 228g last year from southern California to South Carolina its top speed dropped from 48 MPH to 42 MPH - I never connected the dots but likely due to the difference in climate.

engines - I have not done a crompression test but given both engines have 500 hours and run the same RPMs I suspect they are tight as new.

The combined effects of rough bottom paint and warm humid air are a reasonable explanation of a 10% drop in RPMs.

Anyone have any tips for a bottom paint application method to get a smooth finish? Prep by sanding smooth, then apply paint with foam roller and finish sand smooth?

 

[choogenboom]

Trim tabs - fully retracted

Engine trim - balanced them by looking at prop wash in wake as well as syncing the WOT RPM and then trimmed both up until cavitation and then nudged both down slowly while watching GPS speed to eak out the last 0.1 MPH. Pretty sure I left nothing on the table here.

To get maximum planing fuel economy I ran at about 24 MPH with trim tabs down some - does that sound about right?

 

[Stonewall]

I have a 2006 with F250 and the most I have ever gotten out it is 41 MPH. So I think you are in the right range with your set up.

 

[Tuna Man]

choog,
In your original posting I thought you meant the bottom paint was exceptionally smooth, I guess I misunderstood wht you meant by "immaculate paint." I have tried a few different kinds of bottom paints and methods of applying them over the years. What I learned is the obvious, the smoothest bottom is the fastest. On my first boat I removed all of the bottom paint, followed Interlux's instruction manual exactly for the prep coats and finished the boat off with their VC17 teflon bottom paint shot through an airless sprayer. After the paint job the boat actually beat the factory test by a mph or two. The boat actually felt like it got on plane much faster than the old paint job. Unfortunately, this paint did not hold up well and was not designed for the the type of water the boat sat in. Growth began to really slow things down after a month or so. Since then what works best for our waters is to sand the bottom smooth and apply Petit Ultima with a brush and 'tip' (smooth) out the brush marks. Takes more time, but seems to provide a smoother bottom than the rollers do. I also thin the paint slightly if need be. Have not had a problem with bottom growth in a long time.

Just as an extreme example a family member owner a 1989 Marlin with 225 Evinrudes years ago. With the same Teflon super smooth paint that I used (see a pattern here...) he also was able to match the Grady performance specs. That same season he did not use the boat much and let it sit in our almost tropical water for the majority of the summer (we are on the outflow of a nuclear reactor, yes the blueclaw crabs are enormous and glow in the dark) . The week before he hauled the boat we took a ride in the open bay. I do not remember the numbers exactly, but I think the top rpms dropped from 6100 to around 4700, top speed went from about 44mph to 32mph. I realize this is an extreme case, but the bottom really did not look that bad when he pulled the boat. There was definitely growth, but not what we were expecting.

My point is, the condition of the bottom of your boat really is critical to top speed, fuel economy, crusing speed, range, etc.

Hope this helps.

 

[choogenboom]

Thanks Scot. Immaculate paint meant brand new and no growth but I should have been clearer on the texture as that certainly matters.

I plan to experiment with an ultrasonic based growth inhibitor
(here is one example http://www.boatsonic.com/ ) to get out of the whole bottom paint cycle - anyone have any experience with one of these? If not, I'll be the first and report back.

Chris

 

[Grog]

The 1.53 MPG is wishfull thinking, it's a lot of boat. Hot humid air will knock down your HP, not a huge difference but a little loss in the HP and the bottom paint will add up.

Ethanol has less energy per pound but it's proper A/F ratio is roughly double that of gas so in the end you can make more power as long as the mixture is rich enough but your mileage goes down.

 

[choogenboom]

keep your injectors clean

I recently experienced a loss of RPM at WOT on my stbd engine coupled with an increase in fuel consumption. If any of you are interested in the cause, see my posts here with the explanantion.

http://www.yamahaoutboardparts.com/foru ... #post43684

Moral of the story is to pay attention to your WOT RPMs and if you see a drop off good bet its a clogged inlet filter on one or more injectors.

 

[wrobinson]

When my marina went to ethanol fuel I went from 6100 rpms at wot to 5700. This summer they went back to ethanol free and I am now back at 6100 I think the fastest I ever hit with ethanol free was 41 mph on the gps.

My best fuel economy is 1.2 mpg at about 5200 rpms.

 

[choogenboom]

Thanks, that helps explain what I am seeing as I am using E10. I am getting 5500/5700 RPM (port/stbd) and 40 MPH by GPS. My best MPG is 1.3 at about 4500 RPM. Do you get the same RPMs (ie 5700) on both port and stbd engines? I am getting 200-300 less RPMs on the port engine (counter rotating) which Yamaha tech support says is normal and expected, although they had no explanation as to why this happens.

Have you had any problems related to your switch to ethanol? Why did your marina go back and forth on the ethanol?