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LittleWing77 · 10-06-2021, 14:39

Quote:

Originally Posted by marcjsmith

otherwise, fill the tank. log your engine hours. run the engine for 5 hours under normal load, then refill the tank. and calculate your engine burn rate

Quote:

Originally Posted by Marathon1150

In terms of monitoring fuel levels, using engine run time will work. You may need to use estimates of how much fuel the engine uses per hour from the manufacturer and web sources. And then derive data for your boat from run times and how much fuel is added each time you fill up - noting how many hours the engine ran to use that much fuel. IMHO this is the most accurate system.

I used a version of the above methods this past weekend on a short delivery myself:

>Filled up before leaving;
>Motored 9.0 hours at 5 knots (flat calm);
>Filled up the following morning, adding
16.7 litres.
End result: 9.0 hours of motoring used roughly 1.8 litres/hour or 0.5 US gals/hour.
This was an old Atomic 4 gas engine.

Oh, and congratulations on your new boat! Bristol 29s are lovely.

Fair winds,
LittleWing77

Clivevon · 10-06-2021, 14:48

Quote:

Originally Posted by Calif.Ted

Fill it, then fill again after 10-20 hrs run time and you can do the math from there.

Am really struggling to understand why this excellent suggested solution wont work for you until you get the gauge fixed. You just need the discipline to record engine hours in the log - or fit an engine hours meter.

dadster3 · 10-06-2021, 14:52

Is there some reason you can't buy a new gauge?

MJH · 10-06-2021, 15:20

[QUOTE=goodiefun;3423716]I just bought my first boat (1979 Bristol 29.9) which had a "new" fuel tank installed at some point in the last 20 years. Unfortunately, the tank was not installed inline with the opening in the deck (the hose has two almost 90 degree bends in it between the tank and the deck) and the fuel gauge is broken. Does anyone know what I can do to figure out how much fuel is in the tank? I can't use a wooden dowel, or any other type of rigid instrument, to measure the fuel due to the two bends in the hose. Any suggestions would be greatly appreciated. Thanks so much![/QUOTE/]

If possible, get the outside measurements of the tank and do the calculations to determine total capacity. I did this for
my sump tank.

As earlier suggested fill it and then run for measured engine hours, refill and compute burn rate...even if you install a new gauge, you should track fuel burn.

~ ~ _/) ~ ~ MJH

Sailor647 · 10-06-2021, 15:21

The delicate plastic suction lines for our tank tenders failed long ago. So, the metal clean-out hatch covering on the fuel tank (and later the water tanks) was replaced with clear acrylic, making it easy to see how much fuel/water we have in the tank/s.

This solution has worked perfectly for us - when underway or when filling the tank. A simple lift of the sole and a flashlight lets us know how much fuel is left in the tank.

Initially we poured in fuel 20 liters /5 gallons at a time so we had an idea how much fuel (5/10/15/20/30/40/50) looked like on the side of the tank. To be more precise, we could have marked it in some way, but hopefully you get the idea.

There is also a dipstick, but it's difficult to read. And this also lets you see how clean the bottom of your tank is.

Stewie12 · 10-06-2021, 16:07

As suggested calculating your fuel burn rate is the most sensible suggestion.

joelhemington · 10-06-2021, 16:45

Quote:

Originally Posted by goodiefun

I just bought my first boat (1979 Bristol 29.9) which had a "new" fuel tank installed at some point in the last 20 years. Unfortunately, the tank was not installed inline with the opening in the deck (the hose has two almost 90 degree bends in it between the tank and the deck) and the fuel gauge is broken. Does anyone know what I can do to figure out how much fuel is in the tank? I can't use a wooden dowel, or any other type of rigid instrument, to measure the fuel due to the two bends in the hose. Any suggestions would be greatly appreciated. Thanks so much!

Maybe check out something like this https://www.gobiuspro.com/?keyword=w...SAAEgIBUvD_BwE

keyway · 10-06-2021, 17:02

I’m just gonna throw this out there. If you can put a hand on the tank and thump it with the other you will easily be able to detect the fuel level by vibration. It will stop vibrating above the fuel level.

**Wotname** · 10-06-2021, 17:45

Quote:

Originally Posted by goodiefun

I just bought my first boat (1979 Bristol 29.9) which had a "new" fuel tank installed at some point in the last 20 years. Unfortunately, the tank was not installed inline with the opening in the deck (the hose has two almost 90 degree bends in it between the tank and the deck) and the fuel gauge is broken. Does anyone know what I can do to figure out how much fuel is in the tank? I can't use a wooden dowel, or any other type of rigid instrument, to measure the fuel due to the two bends in the hose. Any suggestions would be greatly appreciated. Thanks so much!

Welcome to CF. Welcome to the boating world. Welcome to learning about having to fix things yourself.

For this is the truth for most oil boat owners - you will have to learn to fix stuff you had never ever thought about before - because mostly you can't rely on getting someone else to do it. It is an exciting journey but sometimes painful!

At least you have the collective wisdom of CF to help you out

.

Good luck with the first lesson...

stormalong · 10-06-2021, 17:58

Quote:

Originally Posted by Wotname

Welcome to CF. Welcome to the boating world. Welcome to learning about having to fix things yourself.

For this is the truth for most oil boat owners - you will have to learn to fix stuff you had never ever thought about before - because mostly you can't rely on getting someone else to do it. It is an exciting journey but sometimes painful!

At least you have the collective wisdom of CF to help you out

.

Good luck with the first lesson...

This is the absolute right answer, although I think he meant old and somehow it became oil.

A bad fuel gauge is a minor repair. If you are going to put yourself at the mercy of the boatyard for stuff like this you will end up missing a lot of sailing and will be a lot poorer. Learn to DIY. It's all part of the fun.

ottewj · 10-06-2021, 18:15

Quote:

Originally Posted by goodiefun

Thanks for the suggestions. The boat has been at a yard where they were supposed to make a bunch of repairs over the Spring (including replacing the fuel gauge). Long story short, the mechanic told me a few days ago that he hasn’t gotten to my boat, and that he doesn’t know when he will get to my boat, and that I should come back in the fall since my repairs aren’t critical. My launch is scheduled for tomorrow and I am trying to gauge how much fuel is in the tank before I leave the yard. Guess it won’t be possible to know before I head out. Thanks again!

I used 1/2" OD FEP OD tubing. FEP is a cousin to teflon (ptfe). This material is clear and it will not age, discolor, or break down in the presence of chemicals or fuel. I attached the tubing at the outlet of the tank then ran it vertical to the height of the tank. I used stainless steel compression fittings in the class of swagelok or parker two ferrule fittings. with a simple glance i can see the fuel level in the tank.

stormalong · 10-06-2021, 18:20

Quote:

Originally Posted by ottewj

I used 1/2" OD FEP OD tubing. FEP is a cousin to teflon (ptfe). This material is clear and it will not age, discolor, or break down in the presence of chemicals or fuel. I attached the tubing at the outlet of the tank then ran it vertical to the height of the tank. I used stainless steel compression fittings in the class of swagelok or parker two ferrule fittings. with a simple glance i can see the fuel level in the tank.

Per (I think) ABYC requirements all fuel draw on marine tanks are at the top of the tank. You do not want a loose fitting to drain your tank into the bilge.

rslifkin · 10-06-2021, 18:43

Quote:

Originally Posted by stormalong

Per (I think) ABYC requirements all fuel draw on marine tanks are at the top of the tank. You do not want a loose fitting to drain your tank into the bilge.

That's true for gas tanks, but diesel tanks are not required to draw from the top.

stormalong · 10-06-2021, 18:59

Quote:

Originally Posted by rslifkin

That's true for gas tanks, but diesel tanks are not required to draw from the top.

That may be true. My knowledge of ABYC rules is from what people have said over the years. I would not want a pool of diesel in my bilge any more than gasoline. I have owned three boats with inboards. One gas and two diesel. In my limited experience I have never seen an inboard fuel tank with fittings anywhere but the top.