Starboard engine uses more gas than port

[340DA]

It appears that my Starboard engine uses more fuel when cruising than my port engine. I have twin 7.4l mercruisers with Bravo 3 outdrives... I keep them tuned and I synchronize the RPMs for both engines when cruising. I cruise at about 3200 RPM each

Has this happened to anyone?

What is the cause? and what is the fix???

 

[Do Over]

if you have a Gen it runs off the starboard tank otherwise the gauges are notoriously inaccurate usually.

 

[rondds]

Had the same thing with my previous boat. Never did figure out a cause and the fix is to put more in the tank that has less fuel in it at fill-up time ;-)

I thought maybe it had to do with the fact that one prop is reversed by the transmission and one is not.

 

[sea hare]

Mine are the same way.. except my port engine burns more... up on plane I get 9 gph SB vs 12gph port.... (???)

 

[wellswa]

I found out in my 330 DA that if I run with the tach's synced I burn evenly but if I run using the sync gage they don't burn evenly. Something is wrong with my sync gage so I pay no attention to it anymore. I cruise at about 3200 rpm as well.

 

[rondds]

I struggled with this whole dilemma a few years back on that boat and finally gave up trying to understand it. I went crazy checking the RPM with a digital tach.

If you have a few minutes, here's the story...

http://clubsearay.com/showthread.php/45514-Engines-out-of-synch?highlight=

 

[mistercomputerman]

Had to pitch my props differently...

 

[AMFM3]

Really I don't think we should expect twins to burn exactly the same amount of fuel. There will always be a difference between the two. And as previously mentioned, a genie will pull from one tank and not the other.

My starboard feeds my genie so it always takes a bit more at fill up time.

Mark

 

[Blown284]

I've noted my starboard engine 7.4 burns a little more fuel. I've learned to just live with it...... thought I was losing my mind but it's either (a) I've lost my mind or (b) I have fellow boater friends losing their minds too and now I have company LOL.

 

[vandal]

On 75 gallons used in each tank wth gen off the difference is less than1 or 2 gallons with gen on is around 3.5 to 4.

 

[rcknecht]

I have the same engines as you have... Mine burn the same amount of fuel, but I hardly ever use my generator (At most about 3 hours annually)... I did adjust my throttles to match when the engines are in sync...

 

[Disposable Income]

if you have the quadrajets on these motors, the floats can get saturated and heavy. this leads to one side running richer than the other. over the course of a full tank, my port side was using about 20 more gallons than the stbd. and my gen runs off of stbd. sometimes a simple carb job will even them out. but you HAVE to request new floats

 

[dpmulvey]

The earth rotates clockwise. If you were to run on your starboard engine only your boat would run counter clockwise. Therefore, the additional fuel burn is due to the boat fighting the earths rotation.

~~~~ Cliff Clavin.

Personally, I'm going with the gennie theory. A 4.5kW burns about a gallon per hour or so.

 

[pvan]

no two engine and drive packages have the same internal moving parts friction rates is also a potential reason

Weight port compared to starboard has a direct effect on prop slip that converts to fuel usage