42/700 speed problems/ Fuel positioning...
 

Hi guys,

wonder what is the best positioning of the fuel for absolute top speed in a 42 Lightning with four tanks?

To my knowledge, a V-bottom boat that is as light as possible in the bow, will run faster than a heavy bow, BUT with Fountains stepped hull, it seem like there is not so anymore.. The question to you who actually own one is; -Where do you put the fuel to go super fast?

I am going to visit a customer who bought a 2007 42 with 700s/No6s in 2010 who experience several problems..

1) The boat is having excessive prop slip when going on plan. The engines needs to go all the way up in the 5500 rpm range to make the boat come up on plane at all. Even with the lowest trim possible and with the tabs down. I have never experienced that with any other Fountain before!!

2) This summer, I had the boat to 80 knots/92 mph. on GPS. That was with 8 persons and a bit of fuel onboard. The ECMs have been modified at Whipple before the boat left the US and the engines ran all the way up to 6000 rpm at 92 mph.

I have saved the performance report on my computer from when this boat was advertized by South Austin Marine back in 2010. It shows 107 mph. @ 5350 rpm running 37,5" Hering 6-blade props. It also shows that the boat has 120 gals of fuel (when put in the water I guess).

HOW THE H**L is it possible that the boat runs only 92 mph at 6000? I woder if someone have changed the gears.

Any info about all this will be greatly apprechiated. It is this specific boat: http://www.youtube.com/watch?v=f320F...eature=related

Thanks!! Erik

First things first, don't believe the top speed on the performance report. Mine is exactly what a prop calc would show. I know they test the boats, but I am not sure if they hold brand new, un-broken in engines wide open on each new boat to get a top speed number. He also runs down river in the vids :D My report shows 5 mph higher than my absolute best speed, and 8 mph higher than my every day speed. That being said that boat should still run 105 stock, the whipple mods should get it to 110

Are the props still the same as the test report? You have some really high slip numbers (either prop or tranny) Wondering if someone hit bottom and had the props repaired or worked?

Getting a high x boat on plane is never fun, however that is completely out of wack. In fact those #6 drives have vent tubes to cause cav to get those big props moving, right from the factory, because those big wheels hook too much until they surface.

Start with a stock set of props, the exact ones that fountain spec'd and go from there.

Thanks for the reply. The case is that the props seem to bite, but when trimming up to get the boat to air out they suddenly "slip" or cavitate. Runs into the rev limiter. 6000 rpm is a lot on a 700 and if the boat ran 107 when new, it is some bugs here somwhere...

I remember I spoke to South Austin Marine before he bought the boat and he told me he knew the boat had hit 111 mph it ist best. I believe the previous owner is also a member of OSO and had the ATX427 nickname here. From my poor memory, I (think) I remember to have read that the previous owner did several modifications to the props to get a top speed and that this boat was "dialed in" after houres of testing. Maybe also after the Whiple mods were done. But also that he kept these props for his new 42/700 boat.... It matches with the fact that the boat was sent without props, and that the props came later.

I will check the bottom and see if it is straight. As american boat trailers can are not legal to tow around with in Europe, the owner sold the trailer for a few grand (BIG mistake!), so the guys who have the storage of the boat, has probably put it on some kind of blocks/supports. Probably at the middle of the aft hull... Another mistake!!

So the owner kept the props, and just threw whatever on to sell the boat?

Find out what props he has now, compare them to what fountain spec'd, then ask others. I am sure the stock props will be close even with the whipple mods.

Guess he could have bottom problems, but dirty water from the bottom will not cause a planing problem....even so it would have to be really bad to cause a loss of 20 mph on top speed. Save your self the time of checking the bottom and check thos props.

Anyone in your area have #6 props you can try?

2007 42 Fountain 700 6 drives
 

I have the same boat purchased it late last year. This spring when I tested I could only get to 98 to 99 and all over the rev limiter. The boat had alot of slip. The boat came with 37 x 17 6 blade herrings. One thing I witnessed do not use the mechanical trim indicators use the smart craft drive indicators only. If you are off by .5 on drives this will creat alot of slip. The tabs at 2.5 and the drives 5.5 to 6 for top speed any higher you hit the rev limiter. I purchased a new set of props this summer from herring made a difference on slip and went to 37.5 x 17 x 6 blades. The boat will hit 97 at 4750 and 106 at 5300. I think if a did a soley run with 1/4 tank I could gain at leat 2 mph. The finishes and the blade edge is crucial so if the props are worn and they need to be sent back to herring. I will send my second set out this year to herring.

Coming out of the whole I have no problem tabs down top rpm to 4000 and ease back throttles and lift tabs and the boat is hooked all the way. I have found with the 42 fill the rear tanks this will help bow lift when trimming. Here is a video of my boat couple of weeks ago with 3/4 (240 gals) tanks and three people heading into a head wind. In the video we were at 106 running next to a skater that can hit 130 + varifying my speed on both gps

http://www.youtube.com/watch?v=N-rG5biJI2Y

Ken

As far as the Fountain reports I can say I have had 5 fountains and have hit the numbers on all the test reports. Tested with gps and radar guns for varification. If you have a I phone download the free ap for speed gps and this will give you a reference to make sure your instruments are on.


Keep me posted.

Ken, please don't post any more videos of you walking by me :lolhit:

Love the boat BTW, glad you could make it to the run.

Thank you guys fr all the interesting info and a cool video of a VERY fast 42. I love it :-)

I checked out the 42 last weekend. First in the air and then on the water.

-Bottom were cleaned and made perfect. I checked that the running surfaces were perfectly straight, and they were.
-The drives are set very high. When you look under the boat towards the props, the only thing I can see is the skegs and the props. The "torpedo" of the lower unit is totally above the hull.
Props are clean and without scraches.
-The trim indicator on this boat is very confusing... The scale goes from 1 to 7, and 7 is the most negative trim. To any sane person, low down on a scale (for example 1) should have been far down, and up would be for example 7. This is the case with all the Fountains with Bravo drives. Now here it is the opposite. To make this even more confusing, the needle shows 4,3 when the drives are at the very top position (shallow beach/trailer position). A level trim angle is 6. It means that under normal driving conditions, 7 is max negative trim, and 5 is about a "normal high" prop axle degree. Everything from 4,3 and all the way up to 1 is never possible to reach, as the needle will never get into that area whatever you do... Why this boat is llike this is hard to understand. But the performance report tell me that ithas been like this from it was new. Why they have not put in other bracets on the drives that make the cable run all the way form 1 to 7 is to me very strange.

We topped up the rear tanks and the forward tanks were already empty.

On the water, the boat glides slowly on plane at 2350 rpm with the drives at the bottom and the flaps almost fully down (5,5). But it takes some time. It is also possible to get it faster up with higher revs, but to make it get on plane with much throttle, it is neccesary to pull the throttle slowly backwards to let the props gain grip. If not, the props has a huge rpm and the boat will not plane. At the top speed, trim angle 6 is what gave best speed. It barely touched 100 mph. on a Northstar GPS but nothing more.... And we ran both directions in the same water to get a more precise reading. Over 5,5 in trim, the port prop seemed to loose its grip and the engines over rev. These boats will of course be taken by side wind and that the driver must correct with a little steering angle to one side to get the boat to go straight foreward is natural. But that seem to let one prop get more water than the other (because of the V-bottom). I think that is why the prop looses its grip. It is very frustrating, as the stern feels like it want to "prop ride" like a single enginge outboard ith a high engine can do as it is only the other prop that ha sgrip. One thing that I got to think of would be to increase the diameter of the prop so that it would have more water to work with. Is this a good solution to the problem? The props are six blade Herings with 37,5 inch pitch.

The engines have been tuned with the whipple stage III kit. This boat should fly!! At 110 mph. The kit was added after the boat left the US. I suspect the fuel required to run this kit would be 93 minimum. Here, there are almost no marinas who have more than 91 octane (95 unleaded as we call it here due to the RON/MON case which is different in USA versus Europa). Any input on that would be great. Shouldn't a 700 SCI run on 93 in the first case?? The port engine had some problems as it felt like it was "back firing" maybe 5 times during the half houre test run. It lost its power in a half second. But only at full throttle. This is also the case with a 700 SCI in a Nor-Tech I have been driving this summer. Is this a common problem with 700s? For the poker runs, it should be possible to go WOT on "cruise control" as the hull can handle it with ease.

I would love to get some info and impressions from others with the same boat/engine package. Larger props for better handling and maybe remove the Whipple kit is what I now want to do. But is this right or wrong...?

The port engine has also lower water pressure. 1 bar opposed to 2 on the starboard engine....


Thank you for the input.
Erik :-)

Did you get RPM readings at wide open throttle?

The misfiring you are hearing may be the knock sensors kicking in do to bad or low octane fuel, this will retard the timing and cause a loss in top end power.

The whipple upgradfe is very common, and is a proven set up. Unless you have a fuel quality or fuel flow issue I doubt removing the the upgrade is going to help you. BTW, just removing it is not an easy task.

http://www.whipplesuperchargers.com/...sp?ProdID=1263

One thing to consider is the European version of the 700 NXT is the 662 NXT:

http://www.mercuryracing.com/sterndrives/eu662sci.php

As I recall, because of fuel differences in Europe, they tuned the 700 engine differently such that it makes slightly less horsepower at 662. There could of course be prop issues if they have not been checked, possibly lower pitch to compensate for the expected lower horsepower...

I would call Merc Racing and see if they have ECU's for your motors designed to work with the fuel octane you have. They might actually be the 662 ECU's. As for water pressure, my 42 with 525's has had different water pressures slightly lower on port engine since new.

I have only been able to reach the certificate speed of 87 mph on my boat duplicating their test conditions which was at nearly empty gas, one person, and 40 degrees F (4.4C)!! I froze my ass off. On a normal day I get 82-3.

And one last thing, I know your boat having met the owner when we both found shelter at an unknown marina during a bad storm on Lake Travis. It was one of the first 700's boats on Lake Travis and very fast. He told me he easily got 105 mph any time he wanted. When we met the boat was one month old. He had ordered it new from the factory through S. Austin Marine.

Thank you guys. Great input.

The boat is the same boat that you mention and it was again traded by South Austin Marine to its current owner in Stocholm, Sweden. This boat has original 700 motors, not the 662 EU version.

I will talk to the local guys who mounted the Whipple kit.

I guess you are right about the fuel/knock sensor thing. We need to test it with better quality fuel!!

I will keep you posted. But I think the boat is taken into storage right now. As it has the stage III it should have 865 hp!!

Again, thank you.

I am installing 1/2 spacer on mine next week because my slip is 25%

I let you know how it goes

Thanks. Great. I guess a boat that the props never "loose grip" all of a sudden will go faster in a long run than one that goes potentially 2 mph faster but will have a few hick-ups.

From my experience, slip in itself is not neccesary an issue as long as the boat is faster. For example a single outboard engine boat with extreme engine height and a high pitch prop can go faster than the same boat/engine with the engine down and less pitch althouth it gets a smaller amount of slip with the prop more submerged. But not sure if that applys to inboard engine boats though... Input on this? :)

We are testing next week I let you know

Boat gets on plane easier did not notice any top end lost

Handles and feels better

Dropped my slip to 17%

I am very pleased

Are yours 6 blades also with that kind of slip ?

yes

all 700 nxt #6 boats came with 6 blades frome the factory

prop slip

Why wouldnt 1075 boats run 6 blades , both run #6 lowers why the difference ?

when you go 120 plus mph you always use 5 blades

Your so smart:whistle:

Herring says there are some 1075 boats w 6 blades out there but he says it depends how they are setup , there again why ???

Well I did learn that from you RB

And you did tell me to do the spacers

That's why I am following you to Miami
Because you are the man

Thank you for all you have done

RB you have a 1075 boat will you take it from here please

Its just that Herring couldnt give a definite answer ! trial and error im shure .

1 bar vs 2 bar is quite a bit of difference, 14.7PSI. Is the engine with less pressure the one that was loosing grip over 5.5 trim?
Less pressure could be aerated water to the pick up, and prop.
Or a restriction? causing water to not flow cleanly into the drive and "spill" over the inlet causing the prop to lose grip.
Or a restriction in the coolant path causing higher pressure and lack of cooling to a particular area, excess heat, and the knock sensor issue.
As far as the indicators, turn the label over.

We have 2007 42' Lightning with 700sci's (stock), SSM6/NXT, Hering 6 blade 37pitch props also.
X dimension = "22 7/16 x 18 1/2"

98mph with 5 people and ~half tanks gas, but didn't stay on it to play with trims.
"Drive trim on 3.0 Smartcraft, Planes 2.5 Mechanical"

It does run into stock rev limiters alot up there, eventually went into "hard limp" mode so had to stop, shut off motors, refire to reset the computers due to too many rev limit bumps.
Clearly to get 105mph, we need less proplslip than we are getting.
(Speedo Tattletale Recall is at 104mph, the prior owner clearly has had it there...I seem to recall he had drives more down/in than 3 though, I should call him about it)
I also noticed a "low fuel pressure" warning.
We can only get 89 octane gas in Milwaukee...are people adding Octane Booster to get toward 91?

Fountain test had it at 105mph 5350rpm, drives 5.5, tabs 2.5, 7.4/7.1 lbs boost port/stbd, 45psi water both.

My boat has both trim tab and outdrive MECHANICAL indicators working, but
Smartcraft only has OUTDRIVE numerical display; the trim tabs are not input into the Smartcraft display.
My boat does NOT have the GPS speedo inputting to Smartcraft, so I get no prop slip data either.

QUESTION 1: Tried to see the wiring up under dash but can't see where the GPS speedo should hook into Smartcraft, is that one wire OR is it a Harness Connection?

QUESTION 2:
Should I be using the SMARTCRAFT drive position (3 supposedly neutral/highest speed) or the MECHANICAL drive position to get top speed?
We have the same "opposite" numerical situation on our outdrive position (mechanical vs Smartcraft numbering of drive position, they do NOT match up, max in/bow down is 0.0 on Smartcraft, we've been going to 3 on Smartcraft for "theoretical best top speed position", is this RIGHT?!)

I will have to go to the boat with a digital level and see what "true neutral" is for drives, mechanical AND Smartcraft, to understand this.

We haven't top-speed run too much at all, as we have been "learning the boat" and sneaking up on speeds, handling with great respect for safety before doing alot of all-out top end (for us--I know there are many much faster boats :) ).

Thanks as always to the experienced people here for your thoughts and answers!

XWING.

I have a Fountain with the same setup and also run on Lake Michigan. Not sure about your X dimension numbers though. You need to measure from the crankshaft center line to the bottom of the hull.

Port Washington has 93 octane or you really should consider having your ECM's re-programmed to run on 89. Mercury has a program for this and the HP loss is minimal.

Your GPS antenna has a battery to store the satellite maps that has probably gone dead. Livorsi in Grayslake can replace it for you and that will probably fix your speedometer issue.

The SmartCraft drive trim is the most accurate but you need to calibrate it. Check your manual if you can't figure out how to navigate through the menus.

You need to make a note of the indicator readings when the tabs are parallel with the bottom of the boat. That is the highest you should ever raise them.

At high speeds my boat runs best with the drives level and my tabs level or just below. It sounds like your drives might be a little too high if you are hitting the rev limiters at 98MPH. Please note that very small changes in drive trim can make a big difference in speed / RPM. I have seen similar speeds as your Fountain test sheet so I think they are attainable.

I run out of North Point and head to Milwaukee fairly often, Hope to see you there.

GF?

Got Freedom:
Thanks!
I am surprised there is only 89 octane around MKE, maybe someplace has 91 or 93. Milwaukee Skipper Bud's and South Shore Yacht Club are only 89 too.
Torco octane boost could work, looks like 5 gallons=640 ounces costs ~$300
40 oz Torco in 100gal gas make 89 into 91 octane based on their charts.
5 gallons = 640 ounces = 1600 gallons, adding 18.75 cents/gallon to 89 octane gas cost.
Will likely do this.
We just have the Livorsi GPS speedo, not mapping GPS...but will call Livorsi as you've recommended.
Will have to see what putting the drives down a little does to speed/slip.

I hate to remap the motors for 89 octane/less HP. We WERE thinking about doing Whipple Stage 1 reflash to help under 3000rpm torque (doggy down there with torque management), but not keen on paying $2095.95 TWICE for the exact same computer program. I do computer programming on my cars on dynos...and I reflash (takes 5 minutes) every time I take one still under warranty to dealer, so "$4191.80 for "2 motors", instead of counting it as "one boat getting same programming" is hard to swallow.
Pure profit at this point obviously, "whatever the market will bear" and all, but...

Well we are headed to Miami for the run I let you know how it goes

Been a whie since I have been here. It is great to see your comments and also about the spacers. I find it very logic that the boat handles better with the spacers. But What really accoundt is the prop grip, as having the skeg a little further down should not make much of a difference (in my opinion - maybe I'm wrong). So in essence, I would very much like to have the max prop diametre with the std (extreme) X-dimention. So what is the biggest diametre you can have on a No6 drive? Also, wouldn't a 5 blade be less restrictive than a 6 blade prop? If increasing the diametre, you will get better grip and by going to only 5 blades, you would reduce the drag by the blades..? From looking at the props on "our" 42, it seems that they do not have very much rake. I would assume that a long Vee bottom would run faster with a prop with much rake (more bow lift) as the shafts are so high in the first place..? Am I right or wrong here?

Anyway, in our case, we need to have better fuel for testing before we do any modifications.

Regarding low fuel pressure.. I know the high pressure fuel filters on top of the engine need to be replaced quite often to manage to deliver the right amount of fuel. They are cheap elements and easy to replace.

Happy new year everyone!

Here is a video from a private boat race witha very fast Fountain 38 Lightning with 2x700 with a whipple kit.. It runs 124 mph and accellerate like a rocket! We had some problems passing it with the black MTI in the strange wakes from other boats.. :) http://www.youtube.com/watch?v=Nj7WdiMPVro

I can only tell you the spacer lets me get on plane easier and the boat feels better when your driving it

I have boosted the motors so I don't think I am any slower
And my engine builder thought we needed to bring the rpms back down to 5400 to 5600 for several reasons I can't really explain

The boat still excelerates great

Also I slung a blade and did a ton of damage to the boat because it hit the drive and the other prop
My Insurance company said it was metal fatigue that broke the prop
Dropping the x should help with that a little

Over all I like the spacer my boat is an 2007 the 08 and up have different props

I guess it just depends which boat and props you have

Gnorthga: You used a one-half inch spacer, and went from 25% slip to 17% slip? I wanted to be clear about the size of the spacer you are using, before considering the move myself.

How has your experience and happiness with the spacers been since your letter above in January, how is top speed now vs before, etc?

We also did a Stage 1 computer upgrade to our 2007 42' with 700sci. We got 96 mph at 5900rpm or so, about 29% slip. We had to let off the gas because we were in breakwater area, the lake was NASTY, but our slip is still quite high.
We had gone 98mph at 5400 before the reflash, last year; so basically the rpm/hp bump got us more slip but no more speed, but I had the drives up a bit higher this time than I had last year, to follow the Fountain Performance Report specs.

With some tweaking down of drives should be somewhat better than 29% slip,but not any 17%, or the 16% slip required to hit the Fountain Performance Report's" 105mph at 5350rpm".
Next time will try tucking the drives in more than 5.5 (where Fountain report said was optimal), though that is already a bit tucked in from level.

I graphed out our drives' trim "indicated" settings vs bottom of boat with a digital level...but where to MEASURE the "bottom of boat neutral" is a question. The step in the hull was what I considered "0 degrees/neutral" for the hull in toto, it's a bit different from the keel pad/s.

How hard is it to add a spacer? Doesn't it need two longer shafts transmitting the power down to the lower unit, or is it just splines that slide to adjust to the longer distance?

I love the boat with the spacer it stays hooked up better in rough water

You need longer studs and oiler tubs

check your grounds on the back of the block that can make it back fire if they are lose or corroded

I hear that Gerald

you learned that one the hard way