Starboard engine consumes more than port

[jfboucher]

Hi, I have a 320 '04 with 6.2s Mercruiser and it looks like the starboard engine uses up about 10% more fuel than the port one. Also, top RPM are lower by 200rpm on the starboard side. And no, it is not because of the genset. I have also had the shafts checked for straightness and they came out perfect.

Any ideas ?

Thanks.

 

[mrsrobinson]

What gauge/tool are you using to state these #'s?

 

[jfboucher]

smartcraft on the control panel and I see what I put in when I fill up...

 

[skolbe]

There usually is a dominant engine that uses a bit more fuel. Not 10% more. The RPM's should be similar for both engines at WOT. I just opened mine up a few weeks ago. Mine both hit 5020 and the other hit 5010 RPM's

 

[DS410]

Have you tried the simple stuff like new oil, new air filter, tune-up? Over what period of time have you noticed this difference, and is it consistent? Is your hull clean? Are your trim tabs working properly and do you have them adjusted properly? I really don't know if more drag on one side would make a difference. If you have one, do you use the engine sync?

David

 

[Hampton]

I have your answer! (I think). You probably need to tune your props. Mine was about the same. If you had someone tune them to match, then that is your problem. Your engines both spin one way, and the transmissions turn opposite directions at different gear ratios. They should be the same diameter but different pitches.

Professional prop shops with computerized measuring can re-tune them to your desired numbers. Take down a bunch of stats - W.O.T. rpm on each. Fuel flows at W.O.T. Fuel flows at mid-range and relative RPMS....

Take them to a shop and have them measure them, adjust them, then put them back on and try again. I pulled mine twice in one month after a prop shop "Matched" them for me - bastards.

 

[HavnFunYet?]

I recently had a similar situation and found that the coil feeding power was bad. Once replaced the mechanic found that in addition, I was only running on 7 cylinders. As it turned out, the spark plug wire from the 8th cylinder was not attached properly. In fact, the bad connection caused a short in the wire that resulted in cylinder #8 not even firing!

He replaced the wire and could not believe the difference...it was as though I was driving a different boat. Since the replacement both engines perform perfectly and burn the exact same amount of fuel, AND are not overworking themselves by misfiring and actutally working the way they should.

Imagine the news that one of the 8 cylinders were not even firing and the relief that it was only a wire that fixed it!! My worst nightmare of having a major engine overhaul was averted by a simple fix!!

Check it out, you may be surprised (or may even experience a major bout of relief!).