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Another fuel burn question

Discussion in 'General Yachting Discussion' started by RossC, Jun 4, 2023.

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  1. RossC

    RossC Member

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    My experience is with trawlers running Lehman's burning almost nothing and large sprt fishers burning in excess of 100 GPH. The boats I'm looking at fall in between. These are a few that are on the radar...

    Grand Banks, 135 Lehmans, This is my comfort zone. I know these boats well. Problem is finding a good one or even a variant is difficult. Looked at two today that were advertised in excellent condition with meticulous owners. I didn't even make inside one of them. The other had 45YO original fuel tanks with rust coming through on the corners and lower seams, Top side gel coat was painted but chipping and chawky, gel coat that wasn't painted was cracking in numerous places, cob webs were growing between the rails and gunwales, toilets looked like they hadn't been flushed in quite a while and based on bottom growth the boat appears to have been in the water for the winter. This is one of the better GB's I've looked at and they are asking $130K.

    Hatteras 42 CPMY, 3126 Cat's, 420HP.
    Silverton 453, Cummins B330's, 450HP.
    Silverton 38 Sport Bridge, Yanmar 6LY3-STP's, 440HP.
    Cruisers 405 Express MY, Volvo TAMD74's, 430HP.

    So the question is....If I run the above at trawler speeds will I see similar fuel burn as the GB with Lehman's. My first choice would be a GB or variation of GB with replaced fuel tanks and glassed decks. I have found a few single engine 34's and 36's but they are a little small and I prefer the piece of mind of having 2 engines. My second choice would be the Hatteras. Going to look at the Hatt next week. It looks nice in photos, but the two GB's I looked at today looked good in phots also.

    What do you guys think? Can you run a MY with 400+HP engines at trawler speeds and get decent fuel burn?

    Thanks
  2. abfish

    abfish New Member

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    My Mikelson has twin 480 hp Cummins. I often run at 8 to 9 knots and get around 2 nmpg. As with most boats, if you slow to 6 knots, mileage is even better, but who wants to go that slow?
  3. Pascal

    Pascal Senior Member

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    At hull speed, about 8- 8.5 kts on a 40/45 footer you re going to burn 8-8.5 gph. My 53 Hatteras burns about 9 gph at 9kts hull speed (longer waterline) Engine type and a few feet isn’t going to make a difference. But yes any of these boats will burn more than a trawler although not that much more when considering the big picture.

    Beamer hulls will burn a little more… for instance the 54 Hatteras with 2’ more beam burns 10-15% more at the same speed

    a longer hull will burn more at hull speed but you ll be going faster so in the end it almost evens out. For example the 116 I run now burns 26 gph at 12 kts… while the 84 I ran before burned 22gph at 10.75 kts. Same burn per mile.
  4. Capt Ralph

    Capt Ralph Senior Member

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    Hull speed.
    Horse power required to make hull speed.
    Fresh and reliable engines to make to make that horse power.

    One of my most favorite customer boats had fresh 3208 naturals in a 45' displacement hull. Amazing package.
    Over powered @ 155HP each. They could fast idle forever.
    That same engine was bastardized into grenades over 400HP. What a shame.

    Your other examples make to much HP to be reliable at low speeds.

    If you want MPG and long engine life, remove the after-cooler and maybe the turbo.
    Except for the cat 31**, just avoid them completely.

    I don't see any Detroit engines in your shopping list. Don't ignore one of the most still reliable natural engines ever.

    I do see the ole Lehman starting to be a lil more difficult to keep up.

    So, Your post comparing Lehmans to crap boats and engines don't make much since. Am I missing the question?

    Just keep in mind, anything over hull speed sux fuel and the mid life engines we have been forced to deal with suck, in making any HP over hull speed.

    Please don't take offense, your examples above would make better reef material than family boats.
  5. RossC

    RossC Member

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    My brain works in GPH, so 8 kts / 2 nmpg = 4 gph? That's quite acceptable. About what a classic trawler would do at the same speed. As I get older, I find myself not caring all that much about getting there in a hurry.
  6. RossC

    RossC Member

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    The only 2 on the list that really turn me on are the trawlers and the Hatteras. I've always associated Sea Ray, Cruisers, Silverton, Carver, etc with sketchy quality.

    I do have a few on the list but they are not naturals. 671TI's. I ran 6V92T's and 8V71T's in busses for a while so I'm familiar with them pre-DDEC. I have seen a few 671TI's blown up running hard in sport fishers.

    That was kind of the point of the question. Trying to figure out what's crap without having to learn the hard way.

    No offense taken at all. I appreciate the insight.
  7. RossC

    RossC Member

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    As a side note, the reason the later model euro styled boats like Sea Ray, Silverton and Cruisers are on the list is because the wife likes the euro look over traditional MY and trawlers.
  8. RossC

    RossC Member

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    Not to change the subject, but what's the consensus on single vs twin for near coastal and ICW? I found some nice looking single engine trawlers with bow thrusters. A 34' Marine Trader with a Cummins 5.9 6BTA, a 38' Cheer Men Europa with a New Holland and a 37' Newport with a Lehman. The 34' Trader has had new tanks installed recently. Just need to try one on and see if the smaller size will work.

    In the mean time, the search continues for a twin engine trawler in the 42' range for under 200K that isn't a basket case.
  9. Pascal

    Pascal Senior Member

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    What size boat are we talking about?
  10. Capt J

    Capt J Senior Member

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    Yeah but, in a trawler you're NEVER going to get there in a hurry, and sometimes you WANT/NEED to get there in a hurry to beat weather or darkness. I once went up the Delaware river in a 60' defeaver, we did a painful 4.5 knots for 4 years and a forever and got into an unfamiliar marina on a narrow canal in the dark. I would've glady paid the fuel myself, if we could've run on plane and got there in a reasonable hour. You can run a semi-displacement or planing hull slow to conserve fuel, or speed up cause you have or want to. I would NOT own a displacement hulled vessel as every delivery I've ever made with them was miserable even though I get paid by the day(burning the midnight oil situations), unless I was doing a transatlantic or something similar. It took me 28 days to get from Stuart,FL to Long Island,NY and we were running 12-14 hours a day, miserably.
  11. ranger58sb

    ranger58sb Senior member

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    What's the B330's? Those years, would have been Diamond Series 6CTAs, 450-hp.

    Yes. You may have to occasionally get up on plane for a few minutes, but in general -- as long as you're running at acceptable operating temperatures -- slow is OK. We ran 450s on our previous boat (42 convertible) with 450Cs and fuel burn at about 8 knots varied between 2-4 GPH total (both engines) depending on wind, tide, and current. Our current 58 with twin 900s runs in the 4-8 GPH range at around 8-8.5 kts. Or at about 30 knots if necessary, and I don't yet know what actual fuel consumption rate is, for that.

    Planing hulls sometimes don't track all that well at slow speeds, and you may find being on plane is more comfortable depending on sea states. OTOH, ICW is usually relatively benign... mostly.


    All Chevies. Pre-loved. Or not. Given age, probably previous maintenance will have more to do with it than brand name.


    I'd be happy enough with that set-up. We had a single-screw "trawler" before, worked fine, engine access was great for maintenance. These days, I'd probably treat myself to thruster(s) -- added afterwards, if necessary -- just because I could.

    -Chris
  12. RossC

    RossC Member

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    10 years ago I would have been on board with this 100%. Back when we would blow a few grand in fuel in a long weekend. Now I'm retired and I'm totally OK with dropping the hook and waiting for the tide to change or weather to clear. Don't have anywhere I NEED to be anymore. Yet your point is still valid and worthy of consideration.

    Seems to be a real shortage of decent boats for sale. If it hasn't sold in a few weeks it is likely junk, drastically overpriced or both. It's coming down to what I can find that fits my needs that is not a project. I'm open to both trawlers and MY's.
  13. David Helsom

    David Helsom Senior Member

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    It’s not fair bringing this up when Freebird isn’t around for the popcorn hour.
  14. Pascal

    Pascal Senior Member

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    lol. Good point. :).