One or Two engines??

First Solo · 23 March 2004, 09:15

Having spent ten years having fun in small RIBs it's now time to get serious. I'm beginning to spec out my ideal RIB for everything from cruising to pulling the kids on a board. Arrived at an ideal length of 6.5m (constrained by budget) but unsure on engine configuration so two questions for the forum:

1. Are two engines better than one (say two 75s or one 150hp)?
2. How massive is the difference in running costs between a 150hp out board and an inboard?

Cheers!

MArk

PS any other comments on what RIB to go for would be appreciated, (20k budget).

RLS · 23 March 2004, 09:37

Mark. I have just ordered a 6.4 Rib-X. (www.rib-x.co.uk) These are Falcon made Hulls and tubes from South Africa and then they are finished off over here. Colin is the man you want to talk to at Rib-X, the number is on the website. Very reasonably priced and in your budget. I have gone for a 6.4 with a Mercury 200 Opti on the back. Colin's demo boat had a 140 suzuki four stroke on the back that gives 48 knots I think he said - fast and safe for the family.

patriot · 23 March 2004, 10:09

Mark, I am looking for a similar boat to you and have been thinking about the same problem! The general difference between having twins opposed to a single, is that with twins you ae going to get much more torque, and therefore for pulling people on boards it proves very easy! However you would probally get more speed out of a single as the overall rig would be lighter. I am currently looking at the 6.5, prosport ribs and the 6-6.5 solent ribs. Both look very promising!

Let me know how you get on!

James

jwalker · 23 March 2004, 12:32

It's been discussed lots of times. Do a search, or two.

RLS · 23 March 2004, 12:58

If you are going for an engine of 150hp that has more than enough torque to pull anyone out of the water. One engine will indeed give a higher top end speed. However if you have 2 engines it does have the added safety bonus.
You also have to think of service costs - 2 engines will be more than 1!

patriot · 23 March 2004, 14:12

It also depend how many people tou intend to pull out! Just incase you fancy trying a pyramid!
Just a thought!

Manos · 23 March 2004, 15:11

Is very funny to see my boat with RIB-X sticker on it LOLOL

And my boat is NOT FOR SALE

RLS · 23 March 2004, 15:29

Manos, Have your Falcons arrived yet? How many on order again? - Is it 5?

simmons0 · 23 March 2004, 15:42

Id say with the new engines becoming ever more reliable only 1 engine is required now. Cheaper, lighter, faster.

Have a look at a diesel though. Merc 1.7 dti that im having gives 120hp at the prop and is most commonly fitted in a 6.5m rib. Volvo D3, can just about be squeezed into a 6.5m. Voltswagon marine are producing a rival too.

An engine around the 100hp mark will use about 1 litre per mile, at a cruising speed of 30 mph you'll be using 30 litres. With teh merc 1.7 diesel you'll use around 10 litres. Huge fuel savings if you can stomach the extra cost when you buy the boat.

TIM · 23 March 2004, 15:49

Both have there advantages, But if i was going for Rib again, i would go for one motor..........

The twice we have lost one engine was always down to fuel supply, ie something in the hose... or something like that, but single engine with bullet proof servicing, plugs, fuel and oil.... will run and run..... you can always add a aux in necessary....

Take off with two engines, is wicked but the advantage is lost at the top end........

The biggest advantage though is manoverability..... second to none..... Pitty as Gavin has yet to learn !!!!

Manos · 23 March 2004, 17:36

Quote:

Originally posted by RLS
Manos, Have your Falcons arrived yet? How many on order again? - Is it 5?

No RIBs haven't arrived yet.
Delaaaaaaaaaaaaaaaaaaays

and I'm not happy about it as is been costing me money

New delivery date end April/mid May. Is a long story that I may discuss one day in this forum

Daniel · 23 March 2004, 17:57

Quote:

Originally posted by TIM
... you can always add a aux in necessary....

IMHO Don't entertain this option (been there, done that):

- It'll kick around in the bottom of the boat for months and months, get broken, scratched, sprayed with salt water...
- Will you be able to manuover it over the transom when required? (If you keep it on the transom, chancer are you'll break or loose it soon enough)
- Will it start when you want it to?
- Will it move the boat adequatly when you want it to?

If you are seriously considering an aux. you need twins - i dobout you are in this situation. Buy a single new engine, look after it and carry an anchor and a VHF.

That said and done i'll probably consider twins again in my next boat, but then again my conclusion will probably be a bigger single again.

Manos, with due respect, what value has your pictures added to this thread?

gavin · 23 March 2004, 18:21

I love twins I love the grunt, I love putting twice as much fuel in , excellent manourvilibity, great in turns for pulling boards, etc etc, great relialibity.Ok it knocks a few knots off up top, if you really are concerned about top speed buy a jetski.However double servicing but great for fault finding as you have a complete set of spares on hand, for testing etc.We also have a 6.5 2x75 Fichts approx 1.2 l per nm flat out.We have ran one dry and returned on the other, We lost an engine bolt one day and we returned on motor no 2, we had one stuck in reverse as a cable popped out at the helm, we once had a blocked telltail and returned on the other.Our current fuel delivery is via a manifold we have one fuel hose longer than the other leaving the manifold, and we only ever lose one motor when one of our tanks empties.Two are definately the way to go. cheers gavin

Manos · 23 March 2004, 19:13

Quote:

Originally posted by Daniel
Manos, with due respect, what value has your pictures added to this thread?

Nothing

Richard B · 23 March 2004, 19:31

Mark, if your budget is constraining the hull to 6.5m but leaves you with sufficient funds to consider twin engines, go for one and spend the extra on a longer hull.

Unless, of course, there's another reason why you want two engines (cruising on own in remote area?)

Gavin - what's your max speed on one engine?

Nickytynick · 23 March 2004, 20:02

Dont know if this will work...

http://rib.net/forum/showthread.php?...t=twin+engines

gavin · 24 March 2004, 17:11

I dont think our example is a good example, we run 2 motors which are offset as our hull is a cat, its prob about 10 or 12 kts with 1 motor approx 35 kts with both

Mike C · 24 March 2004, 18:33

Logically, with engines as reliable as they are now, go for one engine.

Psychologically, out in the middle of the channel with you’re family, get two engines.

No answer to the problem. I’ve been musing for years…. Good luck!

Mike C

First Solo · 24 March 2004, 20:47

thanks guys, your combined wisdom is enlightening - what a great site!

MArk

tango · 28 March 2004, 14:22

My Mar.Co 6.4 runs like a bat outtta hell with a Mariner 2.5EFI 175
Easily does 45kt unloaded and will cruise all day at 35 with the bimini open!!!

I have a Mariner 15 at the back as auxiliary, lashed to the mounting plate and virtually unmovable by weather but I dont fly my boat on waves.
The little engine saved my skin once when the reversing cable broke on reverse in a harbor and a line cat was approaching... Just untied the lashings and pulled on the cord, vroom ..... outa here!
Keep the little tyke serviced and running, you never know when you might need it.
It will keep you from becoming a buoy.

Photo below shows my setup

A good idea is to have a four stroke aux, so you only have one tank line and no premix.

Also keep in mind that when cruising with family and kids it is irresponsible to have only one motor.

In Greece where Ribs are everywhere, it is illegal to venture more then 3 miles offshore on a single engine!
And this is one law I wholeheartedly agree with.