300xs fuel use

**bradmd** · 07-20-2018, 07:08 AM

Twin 300xs engines, 150 hrs. No codes ( except still in breakin mode). Wondering why starbd requires 16.7% throttle to achieve 1850 rpm (neutral), using 1.13gph , while the counter only uses 12.7% throttle and 0.99 gph to do the same rpm in neutral? These are on same boat, warmed up, same hours, oil and fuel.

The starboard does seem to run a bit rough compared to the port. Both are easy to start and have no issue idling. Air compressor temp is about the same, block pressure as well. I don’t know much about optimal performance of two strokes, only things I can think of are that maybe the alternator or air compressor is harder to turn on the stbd than port. Water pump impellers are new and water pressure is good on both.

The data posted is from Rinda diacom program. It might have some tests that would help but I just began using it , not that familiar with using it yet. Thx for any info in advance

**gotboostedvr6** · 07-20-2018, 08:54 AM

Run them on small tanks at lower throttle % for 30 min and compare fuel usage.

**davemvegas** · 07-20-2018, 01:12 PM

could be TPS adjustment, or maybe pcm map slightly different firing air injectors. Myself i would not lose any sleep being concerned about fuel mileage in neutral. It will always work out to zero miles per gallon. If after running all day and have a motor burn 10% more on one side. Then i would get to checking the motors over to find something.

**bradmd** · 07-20-2018, 05:02 PM

Yeah I am not terribly worried, and not worried at all about fuel usage, I just notice the port engine sounds so smooth, and the stbd isn’t. Seems like the tensioner really bounces a lot on the stbd, and not on the port. Thought maybe it would be something simple, but u know nothing ever is. Hopeful to do a water test next wk. we can see how they act when the rubber hits the road so to speak