just out of curiousity... 3L inboards economy?

[SimonCh]

Just out of curiosity guys, all these boats you see towing water skiers around, with 3L inboards, what sort of fuel economy would they have? As bad as my 2 Stroke 90 Yam?

Si

[biffer]

I think the inboard would be cheaper to run, more torque at lower revs

[Barrowboy]

Originally Posted by SimonCh

Just out of curiosity guys, all these boats you see towing water skiers around, with 3L inboards, what sort of fuel economy would they have? As bad as my 2 Stroke 90 Yam?

Si

Just how bad is it?

[SimonCh]

Originally Posted by Barrowboy

Just how bad is it?

I think its pretty bad, but maybe i am just a cheapskate!

[matt h]

you do have the red lever on the front of the carb in the up position if its the auto choke version?? up is auto on.... middle is choke permanently on and down is both off!
correctly propped you should get 0.7 litre per Nautical mile as an average.

check the colour of the spark pugs after a good flat out run with no idling. they should be light brownish,, if the middle cylinder is much different. firstly check the mixture on the carbs,. 2.5 turns out, if no change then take the auto choke wax solenoid out and clean it out as you may have some crap in there which will not help ya mpg

[SimonCh]

in fairness i think mine only has 3 settings - Astern, Neutral and Full ahead....

[Dan Gurney]

Originally Posted by matt h

correctly propped you should get 0.7 litre per Nautical mile as an average.

What's your avg cruise speed for that LPN? I have an 85AET and the diff between a 20 - 25 knt cruise (4000-4500) iirc and WOT 5500rpm 34knts is MASSIVE. You can pretty much hear the tank emptying like a bath.

[matt h]

i agree, 22 knots taking it easy. but WOT they will drink, the worst i used to get was just over 1 litre per mile given the weight and prop fitted which was a 13/1/2 x 19 pitch

[A1an]

Originally Posted by Clamchowder

What's your avg cruise speed for that LPN? I have an 85AET and the diff between a 20 - 25 knt cruise (4000-4500) iirc and WOT 5500rpm 34knts is MASSIVE. You can pretty much hear the tank emptying like a bath.

I was shocked at the difference between nailing the throttle and cruising on my SR5 with 75AET, same engine as the 90.

At 21kn at 3700rpm I could manage the magical 1l/m, nailing it having fun the fuel would just disappear. Loved that engine though, the more abuse you gave it the more it loved you.

[paddlers]

Fitted a 135 Mariner on mine last year with a 45 litre fuel tank. The noise of that V6 at full chat means it doesn't last very long but the smile on my face compensates the need to carry extra fuel on board !

Did a 25 mile run last year from Carradale down to Campbeltown and back one morning & emptied the tank from full....!

Taking a couple more jerry cans this year.

[C-NUMB]

Here one web site that covers the consumtion of various mercruiser models, indicative but gives some ballpark figure.
MerCruiser 3.0 Fuel Consumption 135 HP | MPG GPH US Gallons per Hour | 3.0 L 181 mpi/tks.

It would be fun to put a 3.0 L on a SR, the stability would be very good but the weight is maybe litle on the high side?

IMHO the yam 90 is a suprisingly fuel efficient OB for a 2 stroke, and at WOT(33 L/H +- ) there is not much difference even to modern engines.

We use a fuel flow meter on the SR 5.4, and contradictonary what other reports, the speed seams not to affect the economy very much. Sweet spot is 28 knots +-(wheater permitting) and then we do aprox 0,8 l/nm(long distance average, moderate sea satate, fuel and a few kids as cargo). r

At WOT it does aprox 0,85 L/NM and about the same at 22 knots. If less than 22 knots the consumption /nm increases. For sure at cruising speed a 4s or DI 2s would use less.