Outboard Engine Question

Reverend Ludd

Reverend Ludd

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I have a question.
I have just bought a 7m rib and I want to know what to put on it.

I have an option to buy the engine that is already on it.
2005 YAMAHA 115HP FOUR STROKE XL SHAFT
I guess I would then like to get something small as an emergency get me home engine. (I suppose I could always call out the lifeboat if I run out of fuel :) )

Alternately I could fit two engines, maybe 2 Mercury 75hp 2 stroke LS?

Not sure what the benefits of 2 over 4 stroke.

Any suggestions chaps.
 
Last edited:
I would stick with the Yamaha, they are a very good motor, good on fuel, then put a small get you home four stroke on the back, (using the same fuel)
Twin 2/strokes could be thirsty beasties!
 
Reverend Ludd said:
Alternately I could fit two engines, maybe 2 Mercury 75hp 2 strokes ?

Not sure what the benefits of 2 over 4 stroke.

Any suggestions chaps.
Click to expand...

We use two 7.85 metre RIBs commercially
Trips ,training and they form part of a boat Club/Syndicate
So they are in very regular use
We plumped for single 225 HP E Tecs because fuel /oil consumption is important
The power to weight ratio was an issue too, so economic lighter two strokes it was!
IMHO the use of two engines on a RIB brings up the law of diminishing returns, ref fuel/weight etc.
The Yam in question will be ok for pleasure use but no 'Greyhound'.
Ref the two stroke/four stroke issue
You will find the modern generation of Evinrude E Tecs on a par with four strokes ref consumption plus lighter and have more get up and go and 'grunt' than a four
If I was to go for a new four stroke I would plump for Yamaha, just a personal preference with Suzuki next then Honda
I reckon the Yams are the quietest and the Hondas the more laboured if thats the right word, maybe 'sedate' would suit better!
Fuel consumption on all mentioned is very similar
I would try and have a go on the RIB with the engine fitted (unless you all ready have?!!!:rolleyes:), pray what Hull is She?
Oh, our alternative means of propulsion
Paddles:D
 
Thanks for your replies guys

The hull is a BMW although that means nothing to me :confused:

I fancy running about a bit locally, nothing too adventurous I guess so I'm not looking to go at breakneck speed (break back more like).

So I guess favorite is a single right now.
 
Agree. The single is better. 2T motors have better power-to-weight ratio but not if you fit 2 of them! They have better low rpm torque but maybe that's no big deal?

The Yam 115 4 stroke is a good engine though as others have said it wont be a particularly fast rig - 200hp would be better.

Also you need a 25inch shaft by sound of it, and finding used 2 stroke 75hp with XL shaft will be nearly impossible. Actually full on totally impossible. You might have to chop the transom (unless luckily it will handle L not XL motors when in a twin installation, becuase they are at the sides rather than on the centreline). So that's possibly another reason to keep the Yam 115
 
...a BMW.... its not a top gear style rib is it....???

although there's was a Toyota

BLOG_157_pic4.jpg



Oh, and as for your question, certainly wouldn't go for 2 engines, a single Yamaha would do it for me....
 
Reverend Ludd said:
Thanks for your replies guys

The hull is a BMW although that means nothing to me :confused:

I fancy running about a bit locally, nothing too adventurous I guess so I'm not looking to go at breakneck speed (break back more like).

So I guess favorite is a single right now.
Click to expand...

I might be wrong, but could it be BWM ? They used to build them in the sheds at Mercury on the Hamble.

Yam is a fantastic engine, but as others have said quite sedate. I would. stick with a single, by choice an Etec but any of the modern 4 strokes would work well.
 
bwm built animal ribs i believe. I also believe 2 its illegal to sell new two stroke outboards in the u.k.?
 
elioti said:
its illegal to sell new two stroke outboards in the u.k.?
Click to expand...
No, it's illegal to sell engines that don't meet emissions regs, and that in practice outlawed most 2 strokes. But the etecs are special and manage to combine 2 strokeness with low emissions, so they are legal
 
landlockedpirate said:
I might be wrong, but could it be BWM ? They used to build them in the sheds at Mercury on the Hamble.

Yam is a fantastic engine, but as others have said quite sedate. I would. stick with a single, by choice an Etec but any of the modern 4 strokes would work well.
Click to expand...

Ah BWM, you spotted my deliberate mistake then, :o:o

Thanks for all the help guys.

Thing is I'll not be able to afford a new engine so I'm looking s/h.
 
I think you will find a 115 hp a little underpowered for a 7m BWM. In terms of weight the BWM is a slightly above average girl. 7m RIB plus fuel plus crew/passengers is a fair bit to push around.

A 150 direct injection (opti ot etec perhaps) would give you then best compromise on power vs second hand price. BE aware spare parts for both of those engines are expensive. If you were looking at 4 strokes then I would jump up a size bracket again.

This is of ourse all said, not knowing all of the facts, it would be useful to have a bit more detail.

Which year is the RIB? How big are the tanks, how many seats, how many of those seats do you expect to be using, what are you going to use the RIB for, how old is the Yam you have been offered and what is your engine budget?
 
Hi

first of all some data for you
------------------------------------


Hi,

From a test of 150 hp outboards in a swedish boat magazine:

Boat used: Flipper 605 WA (6,15 meter x 2,32 meter, total weight at test 1400 kilogram, water temp 18 deg. Celsius

Honda BF150
Top RPM in test: 6000
Prop used: Honda HR, 3 blade, 20 inch pitch

a) Speed (knots):
At max rpm: 41,7
Minus 500 rpm: 37,2
Minus 1000 rpm: 32,6
Minus 1500 rpm: 29,1
Minus 2000 rpm: 25,5

b) Fuel consumtion (litre per nautical miles):
At max rpm: 1,27
Minus 500 rpm: 1,03
Minus 1000 rpm: 0,91
Minus 1500 rpm: 0,80
Minus 2000 rpm: 0,75

c) Noise (decibel):
At max rpm: 86
Minus 500 rpm: 84
Minus 1000 rpm: 82
Minus 1500 rpm: 81
Minus 2000 rpm: 80

d) Acceleration (sek):
0-30 knots: 9,2
15-30 knots: 6,8

Evinrude E-Tec 150
Top RPM in test: 5100
Prop used: Rebel, 3 blade, 21 inch pitch
a) Speed (knots):
At max rpm: 44,7
Minus 500 rpm: 40,3
Minus 1000 rpm: 33,8
Minus 1500 rpm: 30,0
Minus 2000 rpm: 24,9
b) Fuel consumtion (litre per nautical miles):
At max rpm: 1,38
Minus 500 rpm: 1,19
Minus 1000 rpm: 0,99
Minus 1500 rpm: 0,93
Minus 2000 rpm: 0,83

c) Noise (decibel):
At max rpm: 87
Minus 500 rpm: 85
Minus 1000 rpm: 83
Minus 1500 rpm: 80
Minus 2000 rpm: 78

d) Acceleration (sek):
0-30 knots: 8,0
15-30 knots: 5,6

Mercury Verado 150
Top RPM in test: 6200
Prop used: Mirage, 3 blade, 17 inch pitch

a) Speed (knots):
At max rpm: 41,2
Minus 500 rpm: 36,5
Minus 1000 rpm: 33,4
Minus 1500 rpm: 29,5
Minus 2000 rpm: 25,6

b) Fuel consumtion (litre per nautical miles):
At max rpm: 1,80
Minus 500 rpm: 1,45
Minus 1000 rpm: 1,30
Minus 1500 rpm: 1,04
Minus 2000 rpm: 0,77

c) Noise (decibel):
At max rpm: 87
Minus 500 rpm: 86
Minus 1000 rpm: 83
Minus 1500 rpm: 82
Minus 2000 rpm: 80

d) Acceleration (sek):
0-30 knots: 7,3
15-30 knots: 5,4


Suzuki DF150
Top RPM in test: 6000
Prop used: Suzuki, 3 blade, 23 inch pitch

a) Speed (knots):
At max rpm: 43,2
Minus 500 rpm: 39,4
Minus 1000 rpm: 36,4
Minus 1500 rpm: 32,0
Minus 2000 rpm: 27,8

b) Fuel consumtion (litre per nautical miles):
At max rpm: 1,26
Minus 500 rpm: 1,17
Minus 1000 rpm: 1,04
Minus 1500 rpm: 0,91
Minus 2000 rpm: 0,85

c) Noise (decibel):
At max rpm: 87
Minus 500 rpm: 85
Minus 1000 rpm: 84
Minus 1500 rpm: 79
Minus 2000 rpm: 78

d) Acceleration (sek):
0-30 knots: 8,9
15-30 knots: 5,4

Yamaha F150
Top RPM in test: 5600
Prop used: Yamaha Pro Series, 3 blade, 21 inch pitch

a) Speed (knots):
At max rpm: 44,3
Minus 500 rpm: 40,3
Minus 1000 rpm: 35,4
Minus 1500 rpm: 31,7
Minus 2000 rpm: 26,0

b) Fuel consumtion (litre per nautical miles):
At max rpm: 1,26
Minus 500 rpm: 1,10
Minus 1000 rpm: 0,95
Minus 1500 rpm: 0,84
Minus 2000 rpm: 0,78

c) Noise (decibel):
At max rpm: 87
Minus 500 rpm: 84
Minus 1000 rpm: 83
Minus 1500 rpm: 80
Minus 2000 rpm: 79

d) Acceleration (sek):
0-30 knots: 8,3
15-30 knots: 5,9


Next reliability

we often see Yams and Honda;s with 3000+ hours as these are by far the most common engines used by commercial operators i.e. fishermen, sea farms etc and we also see the odd Suzuki to be fare.

so I would look at the above data and see what fits you needs best.

Dave
 
clydeoutboardservices said:
Next reliability

we often see Yams and Honda;s with 3000+ hours as these are by far the most common engines used by commercial operators i.e. fishermen, sea farms etc and we also see the odd Suzuki to be fare.

so I would look at the above data and see what fits you needs best.

Dave
Click to expand...

All seems much of a muchness really.
For my purposes anyway :)
 
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