fuel consumption

[scottwvyc]

I am still really happy with my new purchase, a 1980 37c with 671 n's. I have noticed the starboard fuel tank sure empties faster than the port side. In about 3 hours of cruising @2050 rpm about 1/8 extra was gone from the strb side tank (2 tanks 165 gallons each). Is this normal? Thanks

 

[Capt K]

Which side does your genset pull from?

 

[scottwvyc]

Didn't run the genset, and for whatever it is worth the crossfeed valve was open , but I notice the valve is above the tank.

 

[Calcutta]

If you haven't already, I would look at the symetry between your props. I had 1 degree difference in pitch between port and stbd. Over a 12 hour day, this equated into a difference of 2 - 2.5 gallons of fuel between the two tanks.

Another telltale hint was that my tachometers were out by 100-150 rpm's.
GAC

 

[Matt]

How about your returns? Are they going to the same tank. My boat has a manifold allowing you to select either tank as the return for each engine.

Matt

 

[Nonchalant1]

Returns should ALWAYS go to the same side as the fuel comes from. Detroits run big volume returns and you can overfill a full tank or quickly empty the other with two returns going to one tank. Correct that one fast. If it looks like it's set right but you still have the problem noted and you don't see a lot of fuel on the water from your exhaust, check the return lines and valves to see if it's really doing what it's set for.

Doug

 

[outbound]

How are you measuring the dif. between tanks? gauges, refill.

 

[Pascal]

don't trust the gauges... refill, run a few hours and then refill again. Guestimate the genset burn... around 1gph in most cases... and obviousy make sure the returns are set to the different tanks.

 

[Traveler 45C]

In addition to tachs on my boat, I have a sync meter.

The first time I ran her I used the sync meter to sync the engines. The tachs were indicated different rpm’s. I didn’t worry about it. The port engine burned more fuel.

The next time I ran her I used the tachs to sync the engines. The stbd engine burned more fuel.

I used a digital tach and measured the rpm’s directly off the engine pulleys. It turns out that my tachs and sync meters are not reading right causing me to run one engine faster that the other. Thus burning more fuel on one side. This may be your problem also.

Verify your tachs are reading right first.