fuel/ mgmt /consumption

[plugger]

Looking for some "BALLPARK" figures<br />for a johnson 115 carbed at different<br />rpm's pushing a 171 mako <br />assuming properly tuned/trimed <br /><br />@2500 =gph<br />@3500 =gph<br />@4500 =gph<br />The 4500 is not wot but in 4 years /seasons its never been pushed further because its fast enough....<br />Any harm in not opening it up for short bursts ?<br />Is there a chart that list this stuf<br />the manual is not being helpful

 

[Hooty]

Re: fuel/ mgmt /consumption

If you're feeding that engine a steady diet of those speeds, I hope you decarbon on a real regular basis. If you don't, those rings are gonna be a mess. That ole johnson would just love for you to hammer it up to 5600+rpm ever time you take it out. <br /><br />As to fuel consumption, I can't be much help with those rpm ranges but as a rule of thumb, at wot it'll burn 10% of it's rated hp in gals/hr. In other words. 115hp = 11.5 gph at wfo.<br /><br />c/6<br />Hooty

 

[rbruce63]

Re: fuel/ mgmt /consumption

But Hooty why would you have excessive carbon build up if these Johnsons came with the economixer oil pump that proportions oil to fuel depending on engine load?

 

[rwise]

Re: fuel/ mgmt /consumption

a lot of engine don't start opening the carb until 3/4 throtle. So you can usualy go to 3/4 throtle and use less fuel than at WOT, and not loose much speed. johny does like WOT!

 

[Hooty]

Re: fuel/ mgmt /consumption

No so much carbon build-up but coking of the rings. Coking is caused by high combustion temperatures brought on by lugging the engine.<br /><br />c/6<br />Hooty

 

[swist]

Re: fuel/ mgmt /consumption

The 10% of HP seems like a good guess for WOT and full load - i.e., it's your worst case. My 225 when run at it's best cruise (somewhere around 4000 rpm, and 1/2 load) will go all the way down to 8 gph or so. So there is a huge range based on all kinds of factors. For one thing, fishing boats tend to have big tanks. I fill my 109 gal tank at 6 lb/gal and I am carrying 650+ lbs of gas around - that's as much as 3-4 people.....