mixman why the trawler?

The only real way to gauge best fuel vs speed would be to measure fuel at different speeds. That accounts for all the variables except weather.
A better way is to keep the wake to a minimum, bow down and just don't obsess over it because the fuel use at any speed and load will be what it is, bad for a car but good for a boat.
 
"Those are the engines I have in my Gulfstar. If you can find those spec sheets I'd sure be interested in seeing them!

Aren't there a lot of factors that go into fuel/rpm/economy? With my power cat I've got NMEA2000 info from my Honda outboards to look at and I can max out fuel economy depending on conditions easily. But it is a semi-displacement hull and a catamaran so things are crazy different from mono-hulls. I find that 5,100 RPM with twin 60hp outboard runs the boat around 17-18 knots and burns about 7.5 gph. That seems to be the sweet spot for this configuration. Yet my Gulfstar is only 6' longer and only has 4hp less but will never, EVER get on plane since it is full-displacement."

Kurt - I am sure I have some data on them on my old laptop which is easy to dig out. It is likely scanned into a pdf if I still have it would you prefer I print it and post it here or send to you some other way?

As far as fuel use comparisons - you really cannot compare moving a boat that weighs more than twice as much packing in all the creature comforts of home to a much lighter boat. I think you will find that you can move much more weight and size for les fuel if you look at it from a 'work done' point of view. Any case your best economy speed will be as Bruce described - at about 6 knots in completely neutral seas.
Hope this helps
 
"The only real way to gauge best fuel vs speed would be to measure fuel at different speeds. That accounts for all the variables except weather.
A better way is to keep the wake to a minimum, bow down and just don't obsess over it because the fuel use at any speed and load will be what it is, bad for a car but good for a boat."

Agreed Bruce - You will see some interesting tendencies in these earlier engines in that they tend to do better at lower rpms and hp loads. The curves are also real handy with the newest lighter diesels to give us a look and make sure we are not overloading an engine.

Hope this helps
 
quote:
Originally posted by smitty477

Kurt - I am sure I have some data on them on my old laptop which is easy to dig out. It is likely scanned into a pdf if I still have it would you prefer I print it and post it here or send to you some other way?

Click to expand...


If you find a PDF simply e-mail it to me via my BE profile. Or you can message me and I'll give you an address to send it to. Thanks!
 
Dang, Bill, I think they're listed both ways on the survey, but you're right about the model number as I think one entry is a typo.

This is how I've been playing with the speed & economy of the cat:

 
I push the throttles forward, I use more fuel. I don't push them so far forward, I don't use as much fuel.
 
Not true for all boats/hull designs. That's what I'm going to miss about my cat (if I do decide to get rid of her); the fuel burn isn't all that different for different speeds in total. 7 knots is about 1.75/gph. 17 knots is around 7/gph. I've looked at the PDQ 34s and the Endeavour 36s and they don't have the same hull design and the same curve for fuel/speed. They're also more than I want to spend considering we're trying to retire before 50 and want as much money on hand as possible for living/fuel/etc.

As a friend of mine (whom you had dinner with in Bimini a few years ago) once said: "if these boats were 20% larger they'd be perfect!"
 
With a planing hull of course that would be true. Freedom is a semi displacement hull and it really doesn't work well beyond hull speed as far as economy is concerned.
 
The Gulfstar is a full displacement canoe type hull, it's really a trawler or as close to one that's not a commercial trawler.
It closely resembles a sailboat hull. She won't do over 9 - 10 knots and adding larger engines won't do much but bury the bow and burn fuel.
 
quote:
Originally posted by boatbum

With a planing hull of course that would be true.
Click to expand...


My cat is also semi-displacement. The hulls are very bulbous until about 4' in front of the engines where they flatten out. My point being that it is possible to have a fuel efficient boat of long-term cruising size that can move in the upper teens, but they're hard to find and command more money than I want to spend.
 
"If you find a PDF simply e-mail it to me via my BE profile. Or you can message me and I'll give you an address to send it to. Thanks"

Found a couple of them - I do not know how to attach a pdf to the BE profile - I did send a message.
 
I don't think anything can be attached here on BE. Did you send me an e-mail or a private message? I don't see either.
 
Kurt what PDF are you looking for? The link I gave earlier in the thread was a PDF to the diesel engines in the Gulfstar.
 
Bill, I just downloaded and saved that, thanks. I was looking for some fuel-burn/efficiency curves (not that it's a big deal on this boat as I'm pretty confident my audio engineering ears will figure that out easily enough :-)
 
The sweat spot is 6-7 knots Kurt. I'll look next time I get to my old office. I believe Bruce sent me some fuel burn, vs rpms efficiency plots. If I find them I'll e-nail them to you.
 
That's great, Bill. No big deal if you can't find it. It really isn't all that hard to figure out. Give me 2 years and you and Jan will be eating dinner on that Gulfstar with us.
 
Hello Kurt,

I sent you an email - I just sent another one as well as a PM with my email address.
The pdf's I have compliment the handbooks that Bill has in that they have some fuel burn and other significant data - but they do not replace handbooks at all.

Hope they help
 
E-mails aren't making it through for some reason. However, I did reply to your PM. Thanks!
 
The email function on BE hasn't worked for me for a long time.
 
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