lcruiser
Just got back from a three-hour tour
Posts: 35
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Post by lcruiser on May 30, 2010 21:27:02 GMT -5
Long story, but I finally have my boat running the best it's ever run. Hat 43C, DD 6V92TA, twin dry turbos, 9A31P injectors (500HP setup), 25.5 x 24 nibral wheels. I can turn right at 2300 rpm's wot and make about 20 knots. However I'm not convinced I'm getting all the "power" out. I'm only measuring about 15psi on strbd engine and around 12psi on port engine air box pressures. This just "seems" low for that kind of HP out of these engines. Does anyone have any performance data for the 6-92 at 500HP for boost pressure??? I have NOT dead racked it yet, just got it running cleanly and all other issues resolved (for now). Thanks, Lc  |
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Post by saltshaker on May 31, 2010 8:36:03 GMT -5
Not sure what the correct amount of boost is but you performance seems pretty slow. I would think you should be able to cruise around 18-19kts and low to mid 20's WOT. I have a 46C Hatteras with 550HP 6V92TA's. I cruise around 22kts at 1950RPM and top out at 26kts at 2400RPM. I am under propped so my performance could be slightly better.
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lcruiser
Just got back from a three-hour tour
Posts: 35
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Post by lcruiser on May 31, 2010 9:14:27 GMT -5
Thanks for the input Salty... Can you tell me what size props you are turning and what your fuel burn rates are at different rpm's?  Also do you know your total weight? yeah, seems "underutilized" to me. I'm holding back about "mouthing off" on the other boards until I have a little more data. If my theory proves correct about dynamic loading the fireworks should be epic... LOL |
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Post by saltshaker on May 31, 2010 13:56:38 GMT -5
Never really tracked the fuel consumption at various RPM's but I believe I burn about 40GPH @1950 running 21-22kts depending on sea state. Last spring we brought the boat home from her winter slip and we saw 24kts @2000rpm with low water and fuel plus a fresh bottom. I think I was getting about .5-1kt boost from the outgoing tide on the Hudson River. We stiill ran between 23-24kts in open water.
I am running 28x28 4blade wheels with 1.75:1 reduction gears. Boat weighed in at 52K fully loaded with fuel, water, gear etc. When we hauled her with an empty water tank and light on fuel, she weighed in at just over 48K.
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lcruiser
Just got back from a three-hour tour
Posts: 35
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Post by lcruiser on May 31, 2010 14:23:43 GMT -5
Wow,, Sheesh, I wish I could get that performance.... I bought a set of 28 x 24 4 blade to try but due to lot's of maintenance and repair I haven't done it yet. Prolly gonna fish her for the summer and tweak next fall. Doing some "thankin" and researching right now on the subject. Oh ps. I have 1.5 red-gear, currently running 25.5 x 24.... me thinks all the "bullshit" about reducing pitch to gain rpm's is a one-dimensional crock... I could be very wrong and will find out when I try the new wheels... thanks for the reply.. Lc |
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Post by banned on May 31, 2010 20:20:52 GMT -5
Check to see if the rack is at or very close to full fuel at WOT under load. If your props are not absorbing 500 HP then your not producing 500HP which would explain the low air box pressure.
You can check this by removing the buffer screw run it up and use a pencil or wood stick to push in on the fuel lever. If it goes up any more than 25 RPM then it's probably not producing rated power. Don't push it up much past 2400.
Brian
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lcruiser
Just got back from a three-hour tour
Posts: 35
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Post by lcruiser on May 31, 2010 21:19:22 GMT -5
Thanks Brian, that's the next test, although will most likely try and fish some first. The "oil" is coming.. OMFG.... I'd still like to have some boost pressure data if anyone has some, comes across some for a similar setup... |
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Post by saltshaker on Jun 1, 2010 19:04:33 GMT -5
Check to see if the rack is at or very close to full fuel at WOT under load. If your props are not absorbing 500 HP then your not producing 500HP which would explain the low air box pressure. You can check this by removing the buffer screw run it up and use a pencil or wood stick to push in on the fuel lever. If it goes up any more than 25 RPM then it's probably not producing rated power. Don't push it up much past 2400. Brian Brian I am turning 2400RPM WOT with 550HP 6V92TA's. Props should be 28x30 4 blades and I am turning 28x28 four blades. Is there any issue with them being underloaded that much? I usually run between 1950-2000rpm and the only downside I've seen is I run a bit cool, around 165. My mechanic is putting in higher temp thermostats to get the temps up a bit. I think he said they are 170 or 172 degrees. |
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lcruiser
Just got back from a three-hour tour
Posts: 35
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Post by lcruiser on Jun 2, 2010 22:10:53 GMT -5
Salty... I'm no expert but I'm fairly certain those engines should run at 180, at least mine do...FWIW..
If you find out different from DD please post it. What do your engines spin up to no load?
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Post by saltshaker on Jun 2, 2010 22:44:17 GMT -5
2500RPM no load. The port engine was just rebuilt and I'm having the mechanic change thermostats in the starboard. He says they were 160's which he felt was keeping the engines too cool. They were put in at the last major by the previous owner. My engines came out of a 44' Rybovich and were rebuilt 2 years before I bought them. They've always run a bit on the cool side but not too bad. I figure now was a good time to set them up properly.
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Also do you know your total weight?
