Port Side Engine Uses More Fuel ?

[Narby_Pup]

Does Anyone Have Information On Why The Port Side Engine On Multihull Boats Consistently Use More Fuel. Have Being Fishing In A 2400 Kevlacat With Twin 140 Suzuki Engines And Port Engine Uses 20 Liters More Everytime. Have Talked To Local Suzuki Mechanic And Said This Is A Common Problem And Can Not Tell Us Why. Does Any Other Ausfish Members Have This Problem And Have They Tried To Improve It, Would Appreciate Any Info.

[finga]

counter rotating props or same??
I can see there would be a difference in same rotation.

[Noelm]

I have owned Cats since who knows when and NEVER noticed any significant fuel difference from one side to the other, I have had both counter and standard rotation, I guess there is always a million to one oddity that the prevailing conditions somehow work one side more than the other, don't know how, but probably the only explaination!

[finding_time]

Noel

Mate in my 5.2 kc the port engine always uses about 3 % more , They are non counter rotating engines , but i do notice that the port engine is always working slightly harder and you have to have slightly more throttle on the engine to match the others RPM! I have always thought its to do withthe way the motors spin that the port engine and hull is gripping the water more and do more work, the starboard side seems to get a bit of a free ride. This is very evident at wot in calm conditions as the port engine will only rev out till 5600 rpm but the starboard will get to 5900 ,6000 but if you drop back the port side to say 5200 the starboard side will loose rpm very quickly to around 5400 as its starts to work.

Ian

[Noelm]

there maybe something in all this, but 20litres is a fair old difference.

[Smithy]

And Ian and Pup, Morgy's old cat used 10 litres or so more on the one side when it had the 2 stroke 60 Evinrudes on it before he put the high thrust 60 Yammies on.

[cormorant]

Dynamics ( prop torque) with non counter rotating props means the port side will be lower in the water and hence the port will use more fuel. Important to try and keep load same on motors and allow them to rev out.

With counter rotating we have only ever notived a slight difference on the port and always put it down to the heavier duty box and the energy it absorbs was our guess. I see a lot of cats that due to poor prop avaliability for counter rotators that motors perform differently. On 2 that have been fully diagnosed it was the so called matched props were not when had propscan computer measured them. Only slightly different but it was enough.

Got to say that with a lot of older cats the moulds were never accurate so a diff in ecconomy could well be hull shape and with so many fittings on the back of boats any difference with water pickups and so on will be noticed.

Have also noted in different parts of Australia dependent on the running motors get (always into swell on starboard quarter on way out. wind in same position every morning ) and the misting motors cop one tends to wear sooner than the other be it port or starboard on commercial boats doing the same run.

The last most common thing is tachos that doon't read accurately- use the computer tacho and see what the real accurate revs are on motors as old tachos can be very inaccuratate. Same old story with boat set up - shit data in shit answer.

[Narby_Pup]

Cheers For Info, The Engines Have Counter Rotating 4 Blade Solas Props. I Must Agree Analog Tachos Are Not Accurate And I Could Have Port Engine Working Harder. If The Difference Was Approx 5 To 10 Litres I Would Not Be To Concerened But To Me 20 Liters Is Excessive.i Will Make A Point Of Keeping Rpm On Starboard Engine Slightly Higher And See What Results I Get. Cheers Again, To Those That Replied And Well Done Smithy For Having The Balls To Start Your New Business And I Hope All Goes Well.