Do two engines equate to one bigger one?

[Nostrodamus]

Just a thought for today.

Does a boat or cat with two engines of say 30hp have the same power of a boat with a single engine of 60hp?

I imagine that power is lost with two smaller engines each having to create drive?

Which is best when driving into an unkind sea?

Just a thought.

 

[john_morris_uk]

I don't know the answer but I saw this boat a couple of days ago and the owner clearly thought that more engines are better.

I'm going to put the picture in another thread and ask a slightly different question.

 

[Nostrodamus]

I don't know the answer but I saw this boat a couple of days ago and the owner clearly thought that more engines are better.

I'm going to put the picture in another thread and ask a slightly different question.

We were in Brighton when a salesman was showing a similar boat to a client. The client pushed the throttle forward and the salesmen in suit, still clutching his I Phone above his head went over the back and in the water... it was good to see.

 

[dash300]

Just a thought for today.

Does a boat or cat with two engines of say 30hp have the same power of a boat with a single engine of 60hp?

I imagine that power is lost with two smaller engines each having to create drive?

Which is best when driving into an unkind sea?

Just a thought.

My view would be that the twin set up apart from manoeverability and safety advantages is that they will be more effective at pushing a boat through the water due to more grip on the water with the increased surface area of two props ie.less slippage.

 

[25931]

Just a thought for today.

Does a boat or cat with two engines of say 30hp have the same power of a boat with a single engine of 60hp?

I imagine that power is lost with two smaller engines each having to create drive?

Which is best when driving into an unkind sea?

Just a thought.

In my experience with cats it doesn't appear to make a big difference but with two engines you could still cope if one were to fail.

 

[[70521]]

We were in Brighton when a salesman was showing a similar boat to a client. The client pushed the throttle forward and the salesmen in suit, still clutching his I Phone above his head went over the back and in the water... it was good to see.

Pictures please

 

[oldsaltoz]

Twin engines will produce less thrust a single after you take into account the fact that two engines of say 40 HP are a lot heavier than a single 80 HP engine.

The advantages of twin engines are better manoeuvrability, on a cat you can the leeward engine in light air conditions, and if one engine breaks down you have a spare that should get you home. Twin engines will use more fuel, but we are not talking about a lot, just a little more. Twin engines tend to give you better progress in rough conditions due to less cavitation , one prop sends to be deeper when other is out.

Good luck and fair winds.

 

[Seatrout]

Twinning up engines has two advantages vis

Stability
Manoeuvrability

However they are as useful as tits on a fish unless the props are counter rotating.

Manoeuvrability: In reverse, you will go straight back instead of pulling to port or starboard.

Stability: A public body had a RIB with twinned 140HP Suzuki OBs and took me out for a demo. One of the most frightening trips ever! As she leaped the waves she veered to starboard by about 15 degrees (every wave)..... the reason.... the props were rotating in the same direction and counter-helm had to be constantly applied.

So NO, you do not get twice the power just the two qualities above.

 

[Billows]

As an experiment once, a 3.5hp and a 2.5hp outboard couldn't put my tender on the plane whereas a 6hp could.

 

[photodog]

Two engines make for extraordinary low speed manoeuvrability... Having had both out drives and shaft twins they re q absolute peice of piss to park......

Twin out drives in particular I found to endow me with god like parking abilities.

But I would suggest that there is not twice the level of safety or reliability afforded by a twin set up...

1) there are twice as many things to go wrong.
2) many ancillaries are only attatched to one engine ( inparticular on our out drive setup..). So if one engine went down we also lost the power steering for the out drives... Battery charging.... Etc.

So I think it's a myth that two engines are twice as safe...

Of course you also have increased weight, complexity of systems... Ergo two fuel tanks with cross overs etc.

If I was going back into power I would opt for a single engine on a shaft with bow thruster....

But really.... Sails are better.

 

[Nostrodamus]

As an experiment once, a 3.5hp and a 2.5hp outboard couldn't put my tender on the plane whereas a 6hp could.

Sounds like boys playtime

 

[antaris]

Twinning up engines has two advantages vis

Stability

Stability: A public body had a RIB with twinned 140HP Suzuki OBs and took me out for a demo. One of the most frightening trips ever! As she leaped the waves she veered to starboard by about 15 degrees (every wave)..... the reason.... the props were rotating in the same direction and counter-helm had to be constantly applied.

That is one weird setup you are describing there; was this an experimental/testing setup of sorts? Were they using leftover materials? Were they plain nuts?