real world fuel usage 120

Ok so here are some real world differences** I just arrived tonite in hollywood fl from the chesapeake bay* I read the post 2bucks started with his flow scan readings* My boat is a 1973 34' marine trader* with a 21''x16 p 4 blade prop tru 2-1 gears** This is my 4th trip to s fla app 1270 miles* So total 7 laps considering up and back* First year I cruised at 1800 rpm used 2.5 gph and the trio took 1910.2 hrs stoped for fuel 3 times** In 09 i slowed to 1700rpm trip took184hrs wit fuel usages of 2.25to 2.38gph* this year I slowed to 1550rpms* trip took 205 hrs fuel usage was 1.75 grh and I had to stop only twice for fuel** I really did not think the 120 lehman could use so little fuel** For me it was a decent $ savings* You be the judge for your self

*thanks 2bucks

The fuel savings is nice but the truly amazing thing is that by reducing your engine revs you reduced your trip time from 1,910.2 hours to only 205 hours.

ha you got me me 191.2 hrs

Rats. I thought you'd discovered a whole new way to vastly speed up a cruiser while reducing the fuel burn.

motion30 wrote:


Ok so here are some real world differences** I just arrived tonite in hollywood fl from the chesapeake bay* I read the post 2bucks started with his flow scan readings* My boat is a 1973 34' marine trader* with a 21''x16 p 4 blade prop tru 2-1 gears** This is my 4th trip to s fla app 1270 miles* So total 7 laps considering up and back* First year I cruised at 1800 rpm used 2.5 gph and the trio took 1910.2 hrs stoped for fuel 3 times** In 09 i slowed to 1700rpm trip took184hrs wit fuel usages of 2.25to 2.38gph* this year I slowed to 1550rpms* trip took 205 hrs fuel usage was 1.75 grh and I had to stop only twice for fuel** I really did not think the 120 lehman could use so little fuel** For me it was a decent $ savings* You be the judge for your self

*thanks 2bucks

Click to expand...

2Bucks, that is some GREAT information and with so many miles travel it would make for some very accurate readings! I have gotten in the habit of running my 135's at 1600 RPM smile, it feels good and I am sure it improves my fuel consumption.

If I'm reading this right there must be other factors in play here.

1800rpm= 191.2 hours @ 2.5 gph
1700rpm= 184 hours @ 2.25-2.38 gph
1550rpm= 205 hours @ 1.75 gph

Andy, I think weather conditions probably came into play there, but it is interesting that overall the time was so little different as a percentage, (about 7%). Motion30 you have a sister-ship to mine, only it is even older, mine being a 1975 hull. I find the sweet revs/speed about 1700rpm by feel and sound and bow-wave, but the significant saving is the extra cutting back to the 1500rpm region by the looks. I don't have a fuel flow meter, but I assume yours is the std Lehman 120, so the reading should translate to mine.

shrimp wrote:
If I'm reading this right there must be other factors in play here.

1800rpm= 191.2 hours @ 2.5 gph
1700rpm= 184 hours @ 2.25-2.38 gph
1550rpm= 205 hours @ 1.75 gph

Click to expand...

*The first year I stoped at marinas every nite** , second year just anchored most nights perhape the in and out of marinas accounts for* some of the extra time

Old fart
this if the first year I was not in a rush to get south, but still traveled alone so.. Coco beach was nice, st augestine. Myrtle beach is cool. The wind blew the whole trip not to much of a problem but all the big boats were inside everything from 65' sport fish to 120' MY Its funny the same parade of boats passing me everyday

You guys may be overlooking something very important. Even a fairly small difference in the way you load your engine will make considerable differences in fuel consumption at specific engine speeds. If your WOT rpm is 2500 (as it should be w a Lehman) and another boat is 2300 your fuel burn will be way different at most engine speeds. So if you're going to compare your fuel burn it can't be apples and apples unless both boats have the same WOT rpm. You may come close comparing fuel burn at a certain number of rpm down from your WOT rpm. So if you want to compare the 2500rpm engine boat w the 2300rpm boat compare at 1900rpm on the 2500rpm boat and 1700rpm on the 2300rpm boat. But it's best to compare boats that are propped the same.*

Old Stone wrote:
OK Mike - How many days for the whole trip? If you are travelling alone, how many hours a day at the helm? I'm jealous!

Click to expand...

*The trip this time of year is 18-20 days* usually sun up to sun down* before the time change,** there was enough day light about 715 am to get underway*to *and by 630 you better have your anchor down** On some days I was tired*and *maybe stoped a little eariler* In the spring the return trip is around 14-15 days due to longer days* of course one must allow for weather* this year I lost 2 day one on the chesapeake and one in Nc* due to strong wind and waves** still it s really cool trip*** you should try it

Eric the point here was not to say* somebody elses* fuel burn*will be x** but just there is a savings to be had by slowing down if you can.* I am sure every boat is different,* mine is just one example* I never thought my boat would ever burn less the 2gph* but it did* for 1200miles

When I did my "maiden voyage delivery" trip it was 530 miles and I burned less than 2 GPH with my 120 Lehman. Most of the time I was at 1700 or 1600 rpm.

That includes*a fair bit of idling time in the locks and waiting for a bridge or two.

Jay,

Sounds like you are/were propped right as that seems like good fuel consumption for that engine speed. I think Marin experienced a reduced burn rate at a higher rpm when he repitched his props. Lower load = less burn.

nomadwilly wrote:
Jay,

Sounds like you are/were propped right as that seems like good fuel consumption for that engine speed. I think Marin experienced a reduced burn rate at a higher rpm when he repitched his props. Lower load = less burn.

Click to expand...

*Yes I can "just" get 2500 rpm at WOT (with calibrated tachometer).

My motor will only turn 2150rpm in gear or neutral at the dock but runs very solid

Your "thottle" cable or speed stop needs to be adjusted.

Verify your tach before you start looking for problems you may not have.

Unless the tach needle (assuming it is an analog tach) physically seizes up at 2150, it is a governor issue.

If the needle did seize but the engine accelerated to high idle rpm it would be obvious by the sound.


-- Edited by RickB on Friday 11th of November 2011 11:06:49 AM

two tachs both agree probably governor adjustment I see the stop on the pump but would have to remove the inj pump to get to it


-- Edited by motion30 on Friday 11th of November 2011 11:52:33 AM

If the*information below*doesn't appeal to you, get a mechanic. You can hurt yourself and the engine if you get governor adjustments wrong.

There should be no reason to remove the governor to set the throttle stops. That is like having to remove an engine to change injectors. Unless you know for an absolute certainty which adjustment does what, don't touch any of them.

Get someone to move the throttle up top*for you. When the wheelhouse*throttle lever is at full ahead, is the governor throttle*lever against the stop screw?

You can disconnect the throttle lever at the governor and see if you can obtain high idle rpm by moving the lever by hand to the stop.

If*doing that*gives you high idle rpm, reassemble the control *then loosen the screw that locks the throttle wire (to the*throttle lever on the governor)*and move the throttle lever to the stop with the wheelhouse throttle*at full ahead and tighten the screw again. Make sure the lever goes back to the idle stop at idle throttle setting.

You can safely make a*SMALL adjustment to*the stop screw*on the speed lever to get high idle*rpm*but don't even think about touching anything else.

If you have the Lehman 120 you should be able to get 2650 rpm at high idle which means full throttle in neutral. Max (rated) rpm under load is 2500.

If the above doesn't appeal to you, get a mechanic. You can hurt yourself and the engine if you get governor adjustments wrong.

It really is no more difficult than adjusting the throttle on your lawnmower.

It is essentially the same but anyone messing around with the governor adjustments on a diesel must understand that tweaking screws without a clear understaning of what those screws do can lead to "issues."

RickB wrote:
tweaking screws without a clear understaning of what those screws do can lead to "issues."

Click to expand...

*I'm with you Carl, 'issues' is a worrying thing.The big problem* with issues is you don't know you have them till it's too late, and usually there is no way back, and any attempt to go back,*leads to dare I say bigger issues.

After reading all sorts of advice in the forums about mechanical issues, I hazzarded an opinion to my long*suffering *mechanic as he was working in the deep recesses of*Sarawana's *engine bay, a head appeared sandwiched between the transducent filament**0 ring*that triggers the biostatic equaliser for the thruster drives, or some such thing.

He gave me one of those Clint Eastwood looks,said nothing and disappeared back into the engine bay.I was lucky that day, I had dodged an issue.

shrimp wrote:...he was working in the deep recesses*... a head appeared ...*

Click to expand...

*

Mark:

In all honesty, I'd rather look at the steel Coot than that mud hen in the slip.


-- Edited by SeaHorse II on Monday 14th of November 2011 11:08:33 AM

SeaHorse II wrote:
Mark:

In all honesty, I'd rather look at the steel Coot than that mud hen in the slip.

Click to expand...

Agreed. *We've got fifty billion coots up here, thirty billion of which live on Lake Washington and which obscure the scenery when you drive across the 520 floating bridge. *Speaking strictly for myself, I'd prefer to see just about anything other than another damn coot-- which is the world's second dumbest bird, by the way--- when I look at the forum.


-- Edited by Marin on Monday 14th of November 2011 11:17:55 PM

I'd prefer to see just about anything other than another damn coot-- which is the world's second dumbest bird,

I see an income plan here , Coot Cook book?

Were working on a Manatee Cook book for the Florida folks.