What happens if.......?!

[Emerald Fox]

Greetings from "Darkest Scandinavia" (Finland)!<br /><br />I posted a question on 15th April, thanks for the replies! I just bought my first boat & outboard engine and wondered how to get a handbook for it. The engine is an Evinrude 20hp, serial = BE20SEEUM. Evinrude sent me an owner's manual (thanks to them too!) and I now know the engine is indeed from 1997.<br /><br /> So, have been on this boat for 3 trips, twice to Helsinki from Sipoo, about 20km each way (there is a nice little harbour called Storören and the boat is parked nearby in the garden of the seller of the boat), and once 18km straight out into the sea to an island. This link shows a nice satellite photo of the coast around Helsinki:<br /> http://virtual.finland.fi/finfo/english/hel_sat.html <br /> You can click on the photo just once to zoom in.<br /><br /> I have been measuring fuel consumption which so far ranges between 42-55 litres per 100km (that's 6 to 8 times more than our car uses, a Mazda 626 station-wagon 1.8, to give some perspective!). We have been driving at all speeds; today I am going to drive the boat again to Helsinki, but this time slow & steady, as economically as I can, measure the fuel consumption again, so then I will really have a good idea how much fuel this thing uses. It's OK for you Americans, when I was in Virginia, West Virginia & Ohio last Summer I noticed that gasoline is half the price of in Europe! But basically I just want to get an idea of how much fuel we need when going somewhere so that we don't run out.<br /><br /> Here's (finally!) my question: this engine takes 2-stroke oil 1:50. What happens if you add less oil (say 1:60,70,80,90,100) or add more oil (say 1:40,30,20,10) ???<br /> What are the advantages/disadvantages?<br /> Just curious.....<br /><br /> Thanking you! Ross Turner

 

[Xcusme]

Re: What happens if.......?!

What are you pushing ?? A Barge??? Just kidding!<br />The general rule of thumb is figure 10% of the horsepower in gallons per hour at WOT. Your 20HP would be 2 gallons per hour, or roughly 7.57 liters/hr at WOT. <br /><br />Playing with the gas/oil ratios can be big trouble. Leaning out the fuel mix to say 100:1 will not provide enough cooling and lubrication under a heavy load. Scored cylinders and overheating (among other nasties) are sure to result. Going the other way and over oiling can foul plugs, gum up the works, lessen power and smoke excessively, which really isn't too bad if you have a mosquito problem.

 

[rwise]

Re: What happens if.......?!

Ross<br />You should find a happy point at 3/4 throttle. Thats just before the carb/s start to open. Give it a try!<br />Richard

 

[phatmanmike]

Re: What happens if.......?!

what type and size boat are you pushing? this would be helpfull info, as what type of water conditions are you running in?<br />you must remember that a boat will be running all day long at 5000 rpm, thats like driving in your mazda all day in just first gear, but trying to go full speed... <br />rwise has a good point.. dont use full wide open throttle unless you are in a big hurry, youll save lots of gas that way and may even help your engine a bit<br /><br />i have a 1988 14hp that uses 1.5 gallons per hour at full open throttle, that would be about 5.6 Liters per hour<br /><br />let us know how things work, and dont mess with that oil mixture or youll smoke your enging and it will be a big garden ornement

 

[Spidybot]

Re: What happens if.......?!

Agreed.<br /><br />If you have a planing design hull and your motor hp is sufficent for making use of the hull's potential (at least 70-80% of max rated hp), you'll get a good km/litre at the lowest possible throttle where your boat is still on clean plane.<br /><br />So, WOT until planing and speed gets up, then back up the throttle as far as possible while maintaining a proper plane.<br /><br />As this provided your setup is OK (motor mount, prop, weight etc.).