Start to Finish: Building Our 50' Skater
#1111
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I just ran across this build a few weeks ago and i figured id make an account to follow it. I was dreaming of using high powered 6.7 cummins engines for marine use. Are they still 6.7 liters of displacement? How are you running standalone ECMs and can you load files via EFI live?
We have talked about a lot of different ways to be able to Dyno it longer but just decided to put them in the boat and finish tuning it on the water in the real world application.
We had several pulls that were several minutes long but could not keep the water temp down. But that will not be a problem in the boat with the unlimited supply of cold water.
The fass pump will just be used for priming the system because we do not want the electrical draw continuous. There is a waterman mechanical pump that will act as a the low pressure lift pump.
The egt will probably be around 1350 degrees when we're done tuning and it's in the boat, they are a little higher right now at the higher rpm levels but there are some things that will make it lower in the boat. The unlimited supply of cold water for the intercooler and engine oil cooler will drop the egt some and the short straight exhaust pipe will help a little also.
I don't want to lower the compression because it will make it a little harder to start and I do need the low rpm torque 800-1500 rpm to be able to get the prop to break loose so I can get on plane. With no boost it makes around 600 ft lbs at 1000 rpm and we think that will be enough to get the boat moving so it will get boost. If not we will put nitrous on it to get on plane.
#1112
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you might be able to get the turbos spinning just by adding a little more fuel at whatever rpm it gets hung up if needed. I added more on mine and it went from being sluggish getting on plane to hopping right up, albeit with a puff of black smoke now when the boost comes on.
#1113
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I don't want to lower the compression because it will make it a little harder to start and I do need the low rpm torque 800-1500 rpm to be able to get the prop to break loose so I can get on plane. With no boost it makes around 600 ft lbs at 1000 rpm and we think that will be enough to get the boat moving so it will get boost. If not we will put nitrous on it to get on plane.
#1114
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you might be able to get the turbos spinning just by adding a little more fuel at whatever rpm it gets hung up if needed. I added more on mine and it went from being sluggish getting on plane to hopping right up, albeit with a puff of black smoke now when the boost comes on.
1. We will probably have a setting for running wide open throttle under the speed that it starts to porpoise, around 650hp.
2. A setting that will run wide open throttle at 110 MPH, around 900 hp?
3. Setting that is how ever fast it will go with the egt safe to run continuous, around 1050-1100 hp
4. Setting that is as much power as we can get out of the engine with the setup we have, around 1300 hp
5. Setting that will go as fast with safe egt as we can on one engine
#1115
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The ability to run different tunes is a nice feature, but I found it really only comes into play on the top end. Takes the same amount of fuel / power to go X mph no matter what the tune level your on. IE: 60mph in CSP-1 at 50% throttle is basically same table values at 40% throttle in CSP-2. Up to the max fuel values in your hottest tune. Runs very linear when you playback data logs against the tune tables from a boat. No gearing changes like a truck.
Without a VGT turbo, ya can't play with boost control. What she makes is what ya get. Leaving timing as your only real "power" variable across all different tunes. But once you find a nice cruising speed, might bump that timing up few deg, and pull a little FP out in that mapped area. You can pick up substantial MPG by efficient mapping to the hull. I basically ran two slots, nice padded cruise tune with limited top end for mileage and EGT, and a full power tune with everything she could supply..
On spooling, pstorti's correct if you fuel it she'll light.. Just another try, adjust, repeat process till makes you happy. Goal, not looking like your on fire while getting on plane. Torque limit tables can help here too. As you mentioned no need to make 2000lbs at 1200rpm. A nice looking torque limit slope up to about 2200R will let it lite, but not blow the props out rolling coal till it does. Unless you want to of course.. lol
As for EGT dyno vs the boat. Prop size / pitch selection makes all the difference. Bigger wheels = increased load, higher EGTs. Smaller wheels, higher RPM, but lower sustained EGT. Couple deg pitch can make +- 200-300 out the pipes. Keeping IAT down will help also. But as pump impellers wear in your average temps will climb too.
Looking good man.
Without a VGT turbo, ya can't play with boost control. What she makes is what ya get. Leaving timing as your only real "power" variable across all different tunes. But once you find a nice cruising speed, might bump that timing up few deg, and pull a little FP out in that mapped area. You can pick up substantial MPG by efficient mapping to the hull. I basically ran two slots, nice padded cruise tune with limited top end for mileage and EGT, and a full power tune with everything she could supply..
On spooling, pstorti's correct if you fuel it she'll light.. Just another try, adjust, repeat process till makes you happy. Goal, not looking like your on fire while getting on plane. Torque limit tables can help here too. As you mentioned no need to make 2000lbs at 1200rpm. A nice looking torque limit slope up to about 2200R will let it lite, but not blow the props out rolling coal till it does. Unless you want to of course.. lol
As for EGT dyno vs the boat. Prop size / pitch selection makes all the difference. Bigger wheels = increased load, higher EGTs. Smaller wheels, higher RPM, but lower sustained EGT. Couple deg pitch can make +- 200-300 out the pipes. Keeping IAT down will help also. But as pump impellers wear in your average temps will climb too.
Looking good man.
#1116
Registered
Limit the torque that's worse than waste on the waste-gate.
With an overdrive in the leg of 0.91 your torque at the prop is going to drop to 1554 ft-lbs @ 3300 rpm. minus the drive loss based on 970hp.
Prop speed is going to be around 1500rpm slower than a 1350 with around the same torque at the prop but much less rpm.
What’s the M8 and its input UJs rated at 3000rpm?
With an overdrive in the leg of 0.91 your torque at the prop is going to drop to 1554 ft-lbs @ 3300 rpm. minus the drive loss based on 970hp.
Prop speed is going to be around 1500rpm slower than a 1350 with around the same torque at the prop but much less rpm.
What’s the M8 and its input UJs rated at 3000rpm?
#1117
Registered
The ability to run different tunes is a nice feature, but I found it really only comes into play on the top end. Takes the same amount of fuel / power to go X mph no matter what the tune level your on. IE: 60mph in CSP-1 at 50% throttle is basically same table values at 40% throttle in CSP-2. Up to the max fuel values in your hottest tune. Runs very linear when you playback data logs against the tune tables from a boat. No gearing changes like a truck..
As for EGT dyno vs the boat. Prop size / pitch selection makes all the difference. Bigger wheels = increased load, higher EGTs. Smaller wheels, higher RPM, but lower sustained EGT. Couple deg pitch can make +- 200-300 out the pipes. Keeping IAT down will help also. But as pump impellers wear in your average temps will climb too.
Looking good man.
Looking good man.
.
Last edited by BigSilverCat; 07-28-2017 at 06:45 PM.
#1118
Registered
Using a waste gate will use more fuel, if we limit the torque by not giving it fuel then it will be more efficient.
We will have the same rpm at the prop as a 1350 at the same speed.
The prop does not know if it has a nuclear reactor (merc 1650) or a bunch of hamsters running in a wheel (Wagler diesel) , So if in a 46 Skater with 1350's and 38 pitch props with 1.4 M8 it will be running 110 mph with 10% slip at an engine speed of 4746, which will have a prop speed of 3390. If in the same 46 Skater with diesel and 38 pitch props with .91 M8 running 110 mph with 10% slip at an engine speed of 3084 it would have a prop speed of 3390. So it will actually be the same prop speed as the 1350 not 1500 less.
The M8 is going to be our weak link in the boat. We know that but are using billet gears instead of cast gears so they might live but we wont know till we try. They do sell the M8 with 1650 and 1750 merc and they have around 1600 ftlb at 3000 rpm so we plan on limiting the torque to where it does not go much above that.
With an overdrive in the leg of 0.91 your torque at the prop is going to drop to 1554 ft-lbs @ 3300 rpm. minus the drive loss based on 970hp.
Prop speed is going to be around 1500rpm slower than a 1350 with around the same torque at the prop but much less rpm.
What’s the M8 and its input UJs rated at 3000rpm?
Prop speed is going to be around 1500rpm slower than a 1350 with around the same torque at the prop but much less rpm.
What’s the M8 and its input UJs rated at 3000rpm?
The prop does not know if it has a nuclear reactor (merc 1650) or a bunch of hamsters running in a wheel (Wagler diesel) , So if in a 46 Skater with 1350's and 38 pitch props with 1.4 M8 it will be running 110 mph with 10% slip at an engine speed of 4746, which will have a prop speed of 3390. If in the same 46 Skater with diesel and 38 pitch props with .91 M8 running 110 mph with 10% slip at an engine speed of 3084 it would have a prop speed of 3390. So it will actually be the same prop speed as the 1350 not 1500 less.
The M8 is going to be our weak link in the boat. We know that but are using billet gears instead of cast gears so they might live but we wont know till we try. They do sell the M8 with 1650 and 1750 merc and they have around 1600 ftlb at 3000 rpm so we plan on limiting the torque to where it does not go much above that.
#1119
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I have to say I've enjoyed following this thread more than any thread I can remember. All I can say is good luck.
#1120
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I know it takes the same amount of fuel to go the same speed but I want the throttle control by limiting the power it is easier to throttle the boat through waves. If I only want to run 80 mph it would be hard to get the throttle to the same spot each time I throttle it if its only half throttle but if it runs 80 mph on the dash I can throttle it and put it back on the dash and keep a more consistent speed.
My experience with EGT is that throttle position, boost, load, RPM and EGT run very linear. The only differences occur with prop changes. A 35P would spin 3850R / 79mph at about 1400F and 75% calculated load. The same dia prop in a 38P spun 3650R / 81mph at about 1550F showing 90% load. All in the same tune. I tested this same math on my 5.9L truck last week pulling a 11k boat up a long hill in VA. Tow haul mode vs regular. Load and EGT tracked hand in hand.
PS. Might check your ECM pinouts for Cruise Control inputs. Depending on the year, if ECM has a valid speed input IE: GPS pulse signal, you may actually be able to add cruise with just a couple steering wheel buttons.
Last edited by kidturbo; 07-28-2017 at 07:39 PM.