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Thread: 460 Jet Mileage suggestions

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    Default 460 Jet Mileage suggestions

    I bought a 1989 24 ft Almar this summer with a 460 Jet. It doesn't have a fuel flow meter and I have only taken it out a couple of times. As one would guess, it is as thirsty as it is loud. I am attempting to figure out what the best RPM for mileage would be and what kind of range/MPG I might expect. It has 2 tanks 40 & 60 gal. Right now I am hoping mileage is no worse than 2 mpg which would give me a max range of 200 miles. I think the previous owner said he ran it at about 4,000RPM which equals about 32MPH on step when it is calm. Guessing a worst case burn of around 15 gal and hour, would give me the 2MPG. I think it is a little better, but not certain. On my trip to PWS, the seas where a little too rough to get on step. I learned the hard way that I burn as much fuel at 15mph in rough water, as I do at 30mph. Anyone out there have a similar set up and what do you see? I would get a fuel flow meter, but it looks like I will be moving next summer, so no need to put any more money into the boat since I will be selling it soon. Thanks, Rob

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    Member SuYentna Dave's Avatar
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    Default 460 carb

    Does have a carb. or is it fuel injected?

    Dave

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    Default 460 numbers

    I have a 1993 460 Redline in a Duckworth 24' with a Hamilton 211. I have a flow scan, and typically run 12-14 GPH. I run it at 3000 to 3200 RPM. Your 4000RPM sounds pretty high, you might want to think of changing impellers if the boat comes up on step well to take it easier on the engine. I would recommend talking to Performance Marine on Dowling (Mike) for more advice on this issue. 2MPG is optomistic with this setup. I can rarely see this if going slow and the water is smooth. The flowscan is really nuce, since it can get you within a gallon or so on how much fuel you have in the tank.

    Jim

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    Jim,
    I think you are right, I think it is 3,000 RPM for cruising, 4,000 was near WOT. So what MPG do you think you are getting with your set-up? I am suprised you think 2 MPG is optimistic, but I do seem to have put a ton of fuel in. I need to be at about 20MPH to stay on step. The ALMAR is very heavy. It is carburated and has a 3 stage Kodiak impeller. I like the boat, just want to figure out how far I can venture out into the PWS. Thanks, Rob

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    Member Dupont Spinner's Avatar
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    Default

    3 miles per gallon would be absolute best scenerio....tide and wind going your way, load minimal and a fuel flow meter you would have a good chance to see over 3 miles per gallon.

    Somethings to help would be a trimable jet or trim tabs and a fuel flow meter.

    My jet boat is fuel injected (454)and a Halimaton 212, I change the ignition and installed a multispark box. I get right about 3 miles to the gallon when I run to Lake Creek from Deshka landing. I like to keep the R's right about 3 grand, plus or minus 300 depending on direction of travel. I do have my nozzle outlet turned over from stock which allows the front to ride higher(I now must keep more weight on the nose as it does tend to porpise(sp?), time for the trim tabs) allowing for more cruise speed without more rpm's. I put a set of Sport Tabs on a friend's I/B Woolridge and it has now made it a better mutlipurpose boat(river & ocean). He can also put his quad or a heavy load of lumber on the dog house without struggling to get on step. With the tabs he can almost force the nose of the boat under the water. They can be installed as not to worry about breaking them off on a grounding.

    North Star fuel flow meters can be found for about $113. Very acccurate units when calibrated.

    This is not something that Robf15e would want to do to a boat that is going for sale but something for those of us staying to consider.

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    Default 2mpg

    2MPG is about the best case for me. My boat is heavy, over 5000lbs, but will get on step the same no matter what is in it, and my top end is about 43 MPH on a calm day in PWS. I could probabily get better mileage if I steped up my impeller, but the current combination works well overall.

    Remember the 1/3 out, 1/3 back and a 1/3 in reserve rule. Even with that I have been a bit nervous when I have been way out, since if the seas change from flat to 4 ft, I think the mileage goes in half. I have trim tabs, but I end up pusing a lot of water and really sucking the fuel.

    My Redline is 340HP, so to some degree the lower mileage is the price you pay for having that performance.

    Jim

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    I have an osprey that's about 8k lbs or so. At 4000 rpm's I am drinking 19-20 gph.
    At 3.7k, I am burning 15-16. I get around 1.6 mpg.
    The gph is subject to the sea conditions.
    Oh yeah, 5.7 EFI 320 hp.

    OOPS!!
    sorry, I just realized your boat has a jet. I am a prop

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    I have been told that the props are more efficient than the jets, and that makes sense. I already have trim tabs. I have played with them a little, but once up on step they only seem to slow me down. They do push the nose down, which might help with the chop a little. For $130 bucks or so, maybe I should add a fuel flow monitor. I like to perform all my own work. Any highly speciallized skills required? I did buy a 15hp kicker to troll with. It worked great on the Deshka moving from hole to hole. I have not had a chance to see how fast it will push the boat. It harldy used any gas though. I have been wanting to go out of Whittier to Knight or Green Island, but now I am not certain that I have the range for it... Maybe I can tow a fuel barge...LOL

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    had the same setup got 1mpg. Put a 150yamaha 4stroke on it, and got 3mpg. And top end was 4 mph faster.

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    Quote Originally Posted by Cape Blanco View Post
    had the same setup got 1mpg. Put a 150yamaha 4stroke on it, and got 3mpg. And top end was 4 mph faster.
    Isn't the boat a little tail heavy now - I'm am of course assuming the inboard is still in the boat. I had thought of doing the same thing, but figured it wouldn't perform well. What kind of boat and what speed do you see? My kicker plate is plenty strong enough for it. Any idea how much your 150hp motor weighs?

    As a second note, any suggestions on aux tanks? I guess I could carry 4 or 5 six gallon tanks, but it would seem to take up a bunch of space, be a hassle to refuel, fire hazard... etc.

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    I had a 1976 24' Almar Jetline, with home-built aluminum cab. I pulled the 460 engine, jet unit and stuff out which weighed about 1200 pounds. I notched out the back end and reinforced it to install the Yamaha 150 4-stroke, which weighed about 480 pounds. Then installed aluminum diamond-plate floor boards and built in a 40 gallon fuel tank under the floor boards where the engine sat. Top speed was around 40 mph., with a little over 3 mpg at cruise. We stayed on the boat up to two weeks at a time. With freezer, generator and fully loaded we did 320 miles on 90 gallons of fuel, which included running the 8 hp kicker some of that time. Attached is a picture of the back end. I understand what you mean about not wanting to go to a lot of time and expense if you will be selling it soon.
    Attached Images Attached Images

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    Sweet looking set up. Looks like you did a custom camper as well for the truck. If I knew I was going to stay longer.... Did you use the boat much in the rivers? I am leary about using it much up here (fairbanks) as I beached it on a gravel bar in the Chena the first time I took it out. Didn't notice the bar 6 inches under the water as I was approaching the boat launch to recover. I had sailed right over it on step on the way down the river, but as soon as I pulled the power.... Took 5 of us to push it off. LOL I used it in the Deshka with no problems. I think many places it might be OK, but not knowing the rivers, makes me nervous.... I do like the sound at WOT though - at least for a while till my ears start ringing!

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    We've had inboard jets for 30 years, but I'm getting too old for the gravel bar incidents, so we switched to ocean boats. With the 150 Yamaha, with cab door closed, we couldn't even hear the engine start.

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    Quote Originally Posted by Dupont Spinner View Post
    North Star fuel flow meters can be found for about $113. Very acccurate units when calibrated.
    Depending on location of gauge and sharpness of your knife about 90 minutes, 2 hours if a beer falls over on the deck while working.

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    Default 460 wooldridge

    I have a 1981 25' wooldridge with a new 460 and 3stage kodiak with totally rbuilt jet new impellers etc. Depending on the load I get 30mph at 34 or 3500 rpm. I redline at 4300rpm. Does this sound normal? Think I could get different pitch on impellers for better speed? Im definetly not short on power.I try not to run over 3500 unless im in the skinny and really need to.

    Also When I got my boat the nozzle was turned over and My bow would ride high but it made the sern dig in and kept me from getting optimal planing surface and made the boat slow. Also when I turned it would slow the boat down so much I would almost lose my plane. Just my experience though.

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    Cape Blanco,
    I sent you a PM to ask more questions about your boat if you have time to BS/Bragg about your craftsmanship. Thanks, Rob

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    Quote Originally Posted by Magnum Man View Post
    I have a 1981 25' wooldridge with a new 460 and 3stage kodiak with totally rbuilt jet new impellers etc. Depending on the load I get 30mph at 34 or 3500 rpm. I redline at 4300rpm. Does this sound normal? Think I could get different pitch on impellers for better speed? Im definetly not short on power.I try not to run over 3500 unless im in the skinny and really need to.

    Also When I got my boat the nozzle was turned over and My bow would ride high but it made the sern dig in and kept me from getting optimal planing surface and made the boat slow. Also when I turned it would slow the boat down so much I would almost lose my plane. Just my experience though.

    Your rpm's are where they should be for a stock setup....more impeller would get you more top end and lower cruise rpm's. But do consider your average load.

    My North River would fishtale/plow before I turned the nozzle over. Cruise rpm before the change was 3300 to 3500 rpms at about 26 to 28 mph. Now I run about 3000 rpm's at 30 mph on the GPS. My top speed is a tad over 55 mph at 4500 rpm's. So now I am looking for a little more pitch. All speeds were on Big Lake or Finger Lake. Without having weight on the bow, ie the kicker fuel tank, it does porpise.

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    have a few nice days have to do the logs on the house will get back to you when the ran starts.

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    Quote Originally Posted by Dupont Spinner View Post
    North Star fuel flow meters can be found for about $113. Very acccurate units when calibrated.

    Where can I find the North Star?

    ALASKAN SEA-DUCTION
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    Blog: http://alaskanseaduction.blogspot.com/

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    Quote Originally Posted by AKBassking View Post
    Where can I find the North Star?

    Sorry about not posting the link earlier but I could not find it.....so here it is


    http://www.boatersland.com/f210.html

    They are the cheapest I could find and the shipping was reasonable.

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