HUMBER WITH TWIN 40HP engines

[martin33100]

Hi, I have been offered a 5M humber with twin 40 Mariner's on it, would this be ok or would it use alot more fuel than a single 60hp or 80hp?, also does two 40's weigh much more than one 60-80hp?

[Jizm]

Originally Posted by martin33100

Hi, I have been offered a 5M humber with twin 40 Mariner's on it, would this be ok or would it use alot more fuel than a single 60hp or 80hp?, also does two 40's weigh much more than one 60-80hp?

probably but you have the back up of two engines, especially good if they don't share fuel supplies or perhaps even seperate batteries. A true back up then. However, 2 motors will use more fuel than one engine of equivalent power not to mention twice the maintenance costs and more weight so not really any performance benefit. I suspect they are relatively old motors?

[martin33100]

Originally Posted by Jizm

probably but you have the back up of two engines, especially good if they don't share fuel supplies or perhaps even seperate batteries. A true back up then. However, 2 motors will use more fuel than one engine of equivalent power not to mention twice the maintenance costs and more weight so not really any performance benefit. I suspect they are relatively old motors?

I don't know the age but they are ex RNLI Mariner 40's, the rib for sale is from the Rib Shop, Southampton (Bursledon)

[Jizm]

can't see it on his site, got a link?

[martin33100]

Originally Posted by Jizm

can't see it on his site, got a link?

It wont be on the site, it is there own rib, they only offered it to me today, do you know of any other 5m ribs for sale in Southampton/Portmouth area?

[Jizm]

Originally Posted by martin33100

, do you know of any other 5m ribs for sale in Southampton/Portmouth area?

Possibly mine, but I can't decide

[Jizm]

Originally Posted by martin33100

It wont be on the site, it is there own rib, they only offered it to me today,

If it's kieron's own boat then it will be well looked after...

[martin33100]

Originally Posted by Jizm

If it's kieron's own boat then it will be well looked after...

I think it belongs to the girl that works there, what rib do you have?

[9D280]

Originally Posted by martin33100

Hi, I have been offered a 5M humber with twin 40 Mariner's on it, would this be ok or would it use alot more fuel than a single 60hp or 80hp?,

What is your planned use? If you plan to use it to cruise at full speed everywhere then maybe. I say maybe because being smaller engines they have smaller legs so there is less drag to double, and if you crusie at around the 20 Knot mark it will make next to no differecne. (drag goes up as the cube of speed for that sort of size of object in water)

If you plan to use it for a lot of dinghy rescue, you can switch one off when you are pootling about waiting for someone to capsise and will save shedloads of fuel!

Originally Posted by martin33100

also does two 40's weigh much more than one 60-80hp?

That will vary. If its Ex RNLI I guess we are talking Mariners. Depending on your choce of 70/80/90 it will for a given half dozen makes & models be a 50 / 50 as to which is heavier..... especuially when you take an aux into account.

As Jizm says, they may be older motors in which case there's a high chance that they will run without a battery, and have a pull start so the "security" thing boils down to twin tanks.

There was a thread a few weeks ago on this subject - worth a read.

[Jizm]

Originally Posted by martin33100

I think it belongs to the girl that works there, what rib do you have?

The girl is Kieron's wife/partner, stef I think?

My boat is a tornado 4.8m with 50HP, 30 knots max.