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Author Topic:   expected range

whalermaine posted 07-28-2003 12:13 PM ET (US)
I have a '98 Montauk 17 with a '98 Merc. 90 2-stroke... I am trying to get some thoughts on expected range/fuel efficiency. I am planning a trip (70-80 miles) and wondering if I can do it on 4 full 6.6 gallon tanks (26 gallons of fuel).
Any thoughts or experience?
Bigshot posted 07-28-2003 12:25 PM ET (US)
I hope so! Keep the rpms under 4500 and you may make it back too.
whalermaine posted 07-28-2003 12:47 PM ET (US)
I am looking on a chart at previous trips taken and where I remember changing fuel tanks. One trip in particular would suggest a 25 nm (or 28 statute miles) +/- range on a 6.6 gallon tank OR 4.25 miles per gallon. I recall probably 90-100% throttle over the course of trip.
If this is accurate I should be able to get there as 4.25 mpg x 26 gallons = 110 miles... impossible to get there AND back. Interesting... maybe, as you say, cutting back to 4500 RPM or closer to 80% throttle (?) would give me closer to 6 mpg and might allow me to get "there and back"... not that I need to do that - just getting "there" is required.
Can you think of any other must do's before departing seeing as it would be about 2.5 hours of continuous engine time at 80%???
Bigshot posted 07-28-2003 01:47 PM ET (US)
Engine life is shortened 90% at WOT. So at 90-100% you won't have that gas or the engine too long. A 90hp will burn approx 8-9gph at WOT, bring the throttle down to 4000 and you will almost DOUBLE your economy.
Sal DiMercurio posted 07-28-2003 03:57 PM ET (US)
Bigshot is dead right on the rpms.
If you run that engine at 90% - 100%, you wont heve enough fuel to get 1/2 way, plus the engine will tell you to go to hell & die from being beat to death.
If you must have that much speed you need a bigger engine & run it at 75%.
Running constantly at 100% is nuts, think how long your car or truck would last if you put it in second gear & floored it & just stayed on it,......not very long my friend.
Theres no such thing as 5th gear on an outboard, it's always in second, so back off the throttle & let that poor engine live a little longer, plus save about 1/2 your fuel.
Sal
jimh posted 07-29-2003 08:30 AM ET (US)
If the engine is in good tune you should be able to get at least 2-3 MPG at cruising speeds.
Using four small tanks is not the way to run that boat. You will be changing tanks every 45 minutes! You will also be leaving some unused gas in each tank. Look into getting one large tank (20-25 gallons).
There is an article in the reference section that discusses on-deck fuel tanks with a strong emphasis on the Montauk. See:
http://continuouswave.com/whaler/reference/onDeckFuelTank.html
Guts posted 08-05-2003 12:13 AM ET (US)
I've gone 43 miles with a jonson 70 two smoker with a 26 (tempo) gal. tank but it was close. you can increase your range if you up grage to a 4 stroke? that is what i did. to go for the long range trips. hope you have a epirp? and some gonads!
Guts
Bigshot posted 08-05-2003 10:05 AM ET (US)
43 miles with a 70? So you burned roughly 13 gallons an hour at 21.5mph cruise.....not possible. That 70 even at WOT will not burn more than 7-8GPH so at WOT say 35mph should fetch you over 100miles.
Sal DiMercurio posted 08-05-2003 04:02 PM ET (US)
43 miles on 25 gallons of gas is WAAAAAY out of line.
Thats less then 2 mpg.
Hell a 6 carbed 200 hp Johnson will get that.
Something aint right here.
Sal
lhg posted 08-05-2003 05:39 PM ET (US)
A Merc 90 running on a Montauk should get about 5 mpg under normal 25-30 MPH cruising conditions. With a Tempo, Moeller or Pate 27 gallon tank under the RPS, you should have a usable cruising range of 120-125 miles under good boating conditions.
Running that 90HP at 90-100% throttle would indicate you were flying along at 40-45mph the whole distance, about 5000rpm?

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Author	Topic: expected range
whalermaine	posted 07-28-2003 12:13 PM ET (US) I have a '98 Montauk 17 with a '98 Merc. 90 2-stroke... I am trying to get some thoughts on expected range/fuel efficiency. I am planning a trip (70-80 miles) and wondering if I can do it on 4 full 6.6 gallon tanks (26 gallons of fuel). Any thoughts or experience?
Bigshot	posted 07-28-2003 12:25 PM ET (US) I hope so! Keep the rpms under 4500 and you may make it back too.
whalermaine	posted 07-28-2003 12:47 PM ET (US) I am looking on a chart at previous trips taken and where I remember changing fuel tanks. One trip in particular would suggest a 25 nm (or 28 statute miles) +/- range on a 6.6 gallon tank OR 4.25 miles per gallon. I recall probably 90-100% throttle over the course of trip. If this is accurate I should be able to get there as 4.25 mpg x 26 gallons = 110 miles... impossible to get there AND back. Interesting... maybe, as you say, cutting back to 4500 RPM or closer to 80% throttle (?) would give me closer to 6 mpg and might allow me to get "there and back"... not that I need to do that - just getting "there" is required. Can you think of any other must do's before departing seeing as it would be about 2.5 hours of continuous engine time at 80%???
Bigshot	posted 07-28-2003 01:47 PM ET (US) Engine life is shortened 90% at WOT. So at 90-100% you won't have that gas or the engine too long. A 90hp will burn approx 8-9gph at WOT, bring the throttle down to 4000 and you will almost DOUBLE your economy.
Sal DiMercurio	posted 07-28-2003 03:57 PM ET (US) Bigshot is dead right on the rpms. If you run that engine at 90% - 100%, you wont heve enough fuel to get 1/2 way, plus the engine will tell you to go to hell & die from being beat to death. If you must have that much speed you need a bigger engine & run it at 75%. Running constantly at 100% is nuts, think how long your car or truck would last if you put it in second gear & floored it & just stayed on it,......not very long my friend. Theres no such thing as 5th gear on an outboard, it's always in second, so back off the throttle & let that poor engine live a little longer, plus save about 1/2 your fuel. Sal
jimh	posted 07-29-2003 08:30 AM ET (US) If the engine is in good tune you should be able to get at least 2-3 MPG at cruising speeds. Using four small tanks is not the way to run that boat. You will be changing tanks every 45 minutes! You will also be leaving some unused gas in each tank. Look into getting one large tank (20-25 gallons). There is an article in the reference section that discusses on-deck fuel tanks with a strong emphasis on the Montauk. See: http://continuouswave.com/whaler/reference/onDeckFuelTank.html
Guts	posted 08-05-2003 12:13 AM ET (US) I've gone 43 miles with a jonson 70 two smoker with a 26 (tempo) gal. tank but it was close. you can increase your range if you up grage to a 4 stroke? that is what i did. to go for the long range trips. hope you have a epirp? and some gonads! Guts
Bigshot	posted 08-05-2003 10:05 AM ET (US) 43 miles with a 70? So you burned roughly 13 gallons an hour at 21.5mph cruise.....not possible. That 70 even at WOT will not burn more than 7-8GPH so at WOT say 35mph should fetch you over 100miles.
Sal DiMercurio	posted 08-05-2003 04:02 PM ET (US) 43 miles on 25 gallons of gas is WAAAAAY out of line. Thats less then 2 mpg. Hell a 6 carbed 200 hp Johnson will get that. Something aint right here. Sal
lhg	posted 08-05-2003 05:39 PM ET (US) A Merc 90 running on a Montauk should get about 5 mpg under normal 25-30 MPH cruising conditions. With a Tempo, Moeller or Pate 27 gallon tank under the RPS, you should have a usable cruising range of 120-125 miles under good boating conditions. Running that 90HP at 90-100% throttle would indicate you were flying along at 40-45mph the whole distance, about 5000rpm?