Fuel tank topping up issue.

[crazy4557]

I now have a 7.5m Cobra rib to experience a different form of boating after many years with planing craft like Fairline etc. Just got fed up with the weather so decided to try something new.

Now, this weekend, launched the boat with full tanks after topping up at the garage (nice price) and we almost flew from Lymington to Cowes and back at 45 knots+. Then another blast in the afternoon over to Newtown Creek for a spot of lunch then back to Lymington. Kids loved it, me too although I was concious of the fuel bill with a 250HP Suzuki Outboard.
Boat recovered back on trailer, which is an interesting job at springs low tide, and back to garage to top up tanks for next trip.
This is where the problem is in that it took only 5 litres and wouldn't take a drop more. Fuel was up to the top of the filler neck but I knew it would take at least 50 - 80 litres to top the tank up.

Do you think maybe an air lock in the tank or are modern engines really that economical :encouragement:

 

[rwilson]

The only thing I can think of is that perhaps when you filled it the first time the angle of the rib relative to the ground was different - in so much as its positioning enabled you to brim her whereas when you tried to refuel her again that angle had changed. The tanks in a lot of ribs are quite shallow to allow under deck fitment so are very sensitive to changes in angle when refuelling.

Unfortunately I don't think you have managed to own the worlds most efficient engine consuming 5lts for your day trip, your estimates of ~65 litres seem about right.

Sounds like you had a good day, I was in Newton creek for lunch on Sunday, but only managed a top speed of 40 knts during the day!!

 

[crazy4557]

The only thing I can think of is that perhaps when you filled it the first time the angle of the rib relative to the ground was different - in so much as its positioning enabled you to brim her whereas when you tried to refuel her again that angle had changed. The tanks in a lot of ribs are quite shallow to allow under deck fitment so are very sensitive to changes in angle when refuelling.

Unfortunately I don't think you have managed to own the worlds most efficient engine consuming 5lts for your day trip, your estimates of ~65 litres seem about right.

Sounds like you had a good day, I was in Newton creek for lunch on Sunday, but only managed a top speed of 40 knts during the day!!

Hello slowcoach

I went to the exact same garage and same pump although I will try raising the car's suspension so that boat adopts an slight angle, might help and prove your theory correct.

Thanks for the suggestion.

 

[benjenbav]

Hello slowcoach

I went to the exact same garage and same pump although I will try raising the car's suspension so that boat adopts an slight angle, might help and prove your theory correct.

Thanks for the suggestion.

One day, it will rain and your crisps will all get soggy. Until then, I suppose there's nothing to be said except...ENJOY!!!