MerCruiser 7.4 and fuel gauge

[yotis]

Hello all, I'm new on this community and as a boat owner (1st boat ever, Chaparral Signature 24 1994, 7 days happy owner) in the area of Marina del Rey, CA.

I have a question which may sound stupid, but can I trust what I see on the fuel gauge while the engine is idling with the boat on the slip? I read that underway is not to be trusted because of the move (boat and ocean). It shows currently half tank and I'm still looking to find out the exact fuel tank size.

Thank you!

 

[Rick Stephens]

No. No gauge is trusted until proven not guilty.

 

[achris]

If you know the size of the tank, then whenever you fill the tank from a point on the gauge, you'll get an idea of the gauge accuracy.
If the tank is 180L, and the gauge shows 1/4, and you put 90L in and it's full, you know you have 90L left when the gauge reads 1/4... Similarly, if it takes 160L to fill, then you know you have only 20L left when the gauge reads 1/4...

An alternative (and addition) is to fit a fuel flow meter. They generally also have a 'tank volume remaining' function. You fill the tank, tell the meter how much in in it and it displays remaining fuel the engine uses it. The 'trick' is to remember to change the meter whenever you fill the tank.

I have a Navman Fuel2100 flow meter, and I like it. Gives instantaneous fuel flow so you have a good idea of how much your engine is using. I get around 150NM out of my 180L tank.

Chris........

 

[Scott Danforth]

Agree, no way to trust a $3 fuel gauge on a new to you old boat

Did you do all the maintenance on your new to you boat?

 

[yotis]

No. No gauge is trusted until proven not guilty.

Thanks.

 

[yotis]

If you know the size of the tank, then whenever you fill the tank from a point on the gauge, you'll get an idea of the gauge accuracy.
If the tank is 180L, and the gauge shows 1/4, and you put 90L in and it's full, you know you have 90L left when the gauge reads 1/4... Similarly, if it takes 160L to fill, then you know you have only 20L left when the gauge reads 1/4...

An alternative (and addition) is to fit a fuel flow meter. They generally also have a 'tank volume remaining' function. You fill the tank, tell the meter how much in in it and it displays remaining fuel the engine uses it. The 'trick' is to remember to change the meter whenever you fill the tank.

I have a Navman Fuel2100 flow meter, and I like it. Gives instantaneous fuel flow so you have a good idea of how much your engine is using. I get around 150NM out of my 180L tank.

Chris........

Thanks for detailed answer Chris!

 

[yotis]

Agree, no way to trust a $3 fuel gauge on a new to you old boat

Did you do all the maintenance on your new to you boat?

Hi,

I know zero to nothing about boats in regarding mechanical topics, so I don't do all the maintenance. The good part is the mechanic which did all the work in the last 10+ years is in the same marina with me and he's a trustful guy. I deal with him during the purchasing process and very few with the owner, took me out on a "very aggressive" sea tour to prove the engine / boat is ok.

To my original question, I asked him today and said that the fuel gauge is pretty accurate. The boat owner said the same.

I'll still do the test which Chris suggested above.

Thanks for your answer.