HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

[butteco]

Am I having a problem with gas mileage (or hourage)... I have a 1976 Evinrude 85HP (4CYL) running on a 16.5 foot runabout. I have 1 gas can in the boat, an OMC 6gallon tank. I wanted to go to a "secret" fishing spot I heard about this morning at the tackle shop so I loaded up the boat and took off to the lake. The spot I wanted to get to is about 15mins away from the loading dock. I dropped in the water and drove STRAIGHT TO THE SPOT, the trip took about 12mins @ WOT (37mph). <br /><br />When I got to the spot I fished for a little while before I needed to get in the tackle box which is behind the gas tank. I braced myself to pick up the tank, only to find it was way lighter than I expected. I fished for a little while longer. Nervous, I decided to motor back to the ramp before I ran out of gas, so 12mins more @ WOT (37mph). <br /><br />All in all I burned about 6 gallons of gas in 25 mins @ WOT. If I calculated things right I am burning close to 14.5 gal/hr. This doesn't seem right? <br /><br />THIS SEEMS WAY TO HIGH TO ME? What do you all think? <br /><br />If it is because I was driving at WOT, would driving at say 25-30mph or 1/2-3/4 throttle get me better gas mileage? <br /><br />I was just really bummed that I can't get to the fishing spot and back comfortably on 1 tank of gas. <br /><br />Any suggestions are much appreciated!

 

[walleyehed]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

This is 100% normal for the 85....you need to cruise around 3500-3700 for best fuel economy.<br />The 85 burns more fuel than the 115 does....and I'm not sure it doesn't develope about the same power.<br />My buddy has an 85 on a 17 foot Deep-V and we burnt 6 gal in 8-1/2 miles at WOT during a crappie tourney...

 

[Boilermaker]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Is that the same "Best economy" RPM range for a late 70's 115 also???

 

[butteco]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Do all outboards get crappy fuel economy like that? I can't afford that - cost me $43 for less than 2hrs!!!<br /><br />AND if I could get the same fuel economy out of a 115HP as a 85HP, I would rather have the extra HP!!! <br /><br />Where can I find a good deal on a 115HP outboard motor?

 

[ratracer]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

From what I've seen, Walleyehed is right about that rpm range pretty much universally giving you the best fuel economy, at least when you're talking about planing speeds. From my experience you'd boost your MPG by somewhere roughly around 25% if you cruised in that range instead of at WOT.<br /><br />I think the newer designs like the Etec and 4 strokes in that power range nowadays burn around 8-10GPH at WOT, depending on the boat, equipment, etc etc etc

 

[dajohnson53]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

I can't argue with the guys who said your 14 gal per hour is "normal" for an Evvy 85 hp. I've never run that engine. I had an Evvy 70 back in the 80s that would burn about 8-10 gal per hour at WOT. I currently have a Johnson V6 235 hp with a jet unit and at WOT it burns around 15 or 16. At "cruise" it burns closer to 12. I go about 4000 -4200 RPM, which is a little more than most do - but it seems to maximize my MPG when I measure fuel flow and GPS speed. Different boat than yours, different engine and I run a jet, so your situation will be different, I'm sure.<br /><br />Again, not disputing the above because they undoubtedly have more personal experience with that particular engine, but it surprises me that you aren't getting closer to 8-10 gal per hour with the 85. I do agree with reducing RPMs by about 25-30 % for maximum mileage. You have to test a few RPMs, gas usage and speed to figure out where your sweet spot is for MPG (which is what you're looking for, no?).<br /><br />What RPM are you getting at WOT? is it what is recommended for your engine?

 

[butteco]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

I get 4200rpm at WOT. Something is wrong with my tach though - at idle it is around 1000 then as I increase throttle it rises and peaks around 6000rpm at 1/2-3/4 throttle, then drops back down to 4200rpm at WOT. The poles are set right and the tach is hooked up properly - I don't know what it's malfunction is...

 

[Dhadley]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

As a rule of thumb any gas motor will need about 1 gallon of fuel for each 10 hp produced at wot. An improper set up will, most likely, add to that consumption.

 

[phatmanmike]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

you could always sell it and buy a kite <br /><br />hey, at least its not as bad as a inline 6 merc ! ! ! ! !<br /><br />mine got 1 mpg !

 

[MarkHPCA]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Butteco,<br /><br />I get about the same with my 120 looper, and yes 3500 RPM is the most efficient. BTW try putting a 2000 Ohm 1/2 Watt resistor accross the send and gnd terminals of your tach it may help. You can get the resister at any Radio Shack store.

 

[CATransplant]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

You've got to start each boating trip with two full 6 gal. tanks if you don't want to be stranded someday.<br /><br />As others have said, back off from WOT for the best fuel economy. You'll run a little slower, of course, but not that much.

 

[G DANE]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

It takes a lot more power to move a boat thru the water than a car on wheels along the road. If you step into your car and just floor it every second you go ( dont try it ) it will consume just about same amount of gas.

 

[Tatorbug]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Reduced power and proper powertrim position can double your milage. I have a 1972 Johnson 85 on a 16' ranger tr-3 and it will run about 38mph at full throttle and drink fuel at 11-12 gal/hr, but backing it to 4200 and 31-32mph, it burns about 7gph.

 

[Rockchalk]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

I ran my 1984 75hp Johnson a bunch for the first time a couple weeks ago. Did a lot of traveling at WOT and DID run out. Total surprise!!! Got an additional tank now...

 

[walleyehed]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

I DO feel for ya with the 85HP, but I just "Had" to have a V6 on my Starcraft last year, so I built me a 200 with GT/XP heads and a few other small features, and this last weekend on a lake only 6-1/2 miles long, moving from spot to spot, in 4 days, I burnt nearly 120 gallons of gas and did not fish between about 10:30 and 4:00 each day....<br /><br />Add 2-1/2 gallons of XD-50 @ 23.00/gallon too.<br /><br />EDIT: Now that I think about it....I'm in the market for another 115.

 

[rayjay]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Here is an interesting chart from the nissan site. <br /><br /> http://www.nissanmarine.com/tech_talk/gas_mileage.html <br /><br />These are more refined than your old 76 model and the bigger ones still use a lot of fuel.

 

[CATransplant]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Just got back from the lake. I was out for about two hours. Mostly trolling, with probably half an hour running near WOT. Ancient 1958 Johnson 35 hp used about 2 gal. of fuel.<br /><br />Speed has its price, I guess. I can do around 20mph cruising at 80% throttle. It gets me there, and the motor will troll down to 1.5 mph (GPS) and keep it up as long as you like.<br /><br />I don't envy walleyehed. A couple of trips like that would have paid for my whole boat, motor, and trailer. I think I'll keep it.

 

[dajohnson53]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Originally posted by butteco:<br /> I get 4200rpm at WOT. Something is wrong with my tach though - at idle it is around 1000 then as I increase throttle it rises and peaks around 6000rpm at 1/2-3/4 throttle, then drops back down to 4200rpm at WOT. The poles are set right and the tach is hooked up properly - I don't know what it's malfunction is...

People have been writing that carb'ed outboards are gas hogs and that you can improve economy by reducing speed and cruising RPMs. All very true.<br /><br />But, I keep coming back to thinking that 14 GPH at WOT is way too much for an 85 HP - and now with the above info, I'm wondering if the boat's setup is impacting this. You do't really know until you get the tach issue resolved. I'd try to get the tach issue remedied - either by fixing the current one, or buying and installing a new one. The teleflex gauge website has a technical assistance page which I've found to be a handy general guide for troubleshooting gauge problems. I'd start there. Frankly, standard issue tachs are pretty cheap and very easy to install. YOu might consider that. <br /><br />Because, you need to figure out what your actual WOT rpms are, determine if it is in the recommended range for your engine, adjust prop, trim, etc. as necessary to make it run within the recommended RPMs - and then figure out what your wOT GPH is at that point. I'm not saying this is the case, but it could be that you have a prop/trim problem which is impacting your mileage at WOT and therefore overall cruising mileage.

 

[rustierjeeps]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

I have the exact same motor, an Evinrude 85 hp 4 cyl. The motor has not been run in years, and I was wondering if anyone could tell me the oil to fuel ratio? I drained the tank last night, and I want to flush it and make an attempt at starting it. Any advice would be appreciated! Thanks. Jeremy

 

[Rockchalk]

Re: HELP!!! Am I having a problem w/ Gas MPG ??? (6gal 25mins)

Originally posted by rustierjeeps:<br /> I have the exact same motor, an Evinrude 85 hp 4 cyl. The motor has not been run in years, and I was wondering if anyone could tell me the oil to fuel ratio? I drained the tank last night, and I want to flush it and make an attempt at starting it. Any advice would be appreciated! Thanks. Jeremy

It should be 50:1. Do a search on here about "fuel ratio" and "restarting engine" and you sould get loads of good info. You will find with your search that a carb re-build and new impeller will be suggested and in order. Thats what they told me and what I did. Worked well... Good luck!