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Carlos Maldonado

280 signature performance test

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Hi everyone, I was wandering if somebody knows where I can find a performance test made to  Signature 280 preferably of 2006. That is my boat and I mainly want to know the speed and revs ratio of this boat using twin 5.0l CID carburated Mercruiser engines with Alpha One Gen II sterndrives pushed with 14 3/4 X 16 4-blades SS props. I use the boat on salt waters through the caribbean and wanted to know what is the speed/revs average that saves the most fuel. Right know my boat cruise at 30 MPH at 4000 RPM's and wanted to know if this ratio is OK or if I have to make any correction to either props or engine adjustment.

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Call the guys at Hill Marine and give them your numbers. They will dial you in if new props are needed but also tell you if they are not needed. Good people. 

https://www.hillmarine.net/

 

You sound pretty close to where you should be in my opinion. Might be able to get the RPM's down just a bit to save fuel. 

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Not a cruiser owner but from the standpoint of the engines, WOT is 5000 RPMs assuming they are MPI engines. That means you are cruising (long distances?) at 80% of your max. That can't be good in the long run. I wouldn't want to cruise over 3500 RPMs at whatever speed that gives you.

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Maybe I am not understanding?? But we are talking about cursing speed, not top end. Yes?

I have a Sig 290 with twin 4.3L. Ok different boat with different engines but the same does hold true. I do about 30M.P.H. (26knots) doing about 3200 to 3300 RPMs. Which give me about 22 GPR fuel rate. Anything less or more, brings down my MPG rate. Roughly, the same should true with this boat. 

Doing about 30 mph or any boat's (sweet spot) getting the most MPG out of the engine/s is a good thing for a long trip. Why push the engine/s and pay more at the fuel dock??

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His engines are OHV Chevies in a boat with carburators at about 220 hp, 4800 rpm & rev limited. So it falls into the 2800 to 3200 best cruise range. Most efficient " Breathing speed of the engine." 

I think your engines are tied to possibly very slippy props.  Check the props for damage. 

My 5.0L carb engines do almost a perfect 1,000 rpms for each 10 mph increase. Average deep V hulls. 4,800 rpm equals 45 mph.  That iis with a VERY blow out proof prop that eats hp.

Almost forgot......... Hot salt water is MASSIVE drag of weeds & animals stuck to the bottom.  Pull it & clean it  ??   Some areas are a monthly job if docked in salt.

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I had a 2003 280 sig.

At around 25 mph was my most efficient, rpms around 3600.

15 mph? You wont even be on plane.

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I have 2005 270 Sig with twin 4.3 VP duoprops, so similar hull, different power and props.

I can't give precise answer, but best feeling cruise for me is about 28-30mph with RPMs around 3,000-3,500 +/- (I haven't been on the water for a few months!!), with engines trimmed a bit in Chesapeake Bay water.

I agree with jeffk that 15mph is not the answer for this hull, at least.  That would be plowing through the water

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Thanks to all for your replies. I haven't got a chance to test my boat because of high winds that are causing rough tides on my boating area. As soon as winds calm down I'll do the test and post results.

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I agree with what the others have said.  These hulls work best at about 28 - 32 mph which is about 3100 to 3500 rpm.  Anything less than that and the boat feels sluggish and starts to fall off plane.  I also get my best fuel economy when cruising in that rpm/speed range.

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15mph your plowing water and not knowing how to drive that boat.  Good cruising speed for just about any boat is between 20-30mph at around 3-3500 depending.

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Beating a dead horse ... 15 mph is a semi-displacement speed. Trying to go 15-17 mph in planning hull results in the worse economy one can achieve. The planning hull is designed to mount its own bow wake. The semi displacement hull is designed to push it aside without raising its bow too much. The planing hull has two economical speeds ... displacement speed and planing speed.

The chart below, which is in line with all comments above, shows the fastest economic displacement speed @1400 rpm for coasting and most economic planning speed @3400 rpm for cruising. This is for my boat: 2007 Sig 270, single VP8.1L 375 hp engine and DPS-A drive. The hull has a bottom barrier coat and lost around 4 mph of the top speed, used to reach 50 mph before painting.

large.5ada3654a28d4_0000FUELECONOMY.jpg.

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