what speed should my rib achieve?

xpertski · 28 October 2005, 00:51

hey all, just wondering what speed my humber ocean pro 6.3m should reach, with a 140hp suzuki and standard prop? currently i cant top 39 knots, and im sure i heard in a test report that the same boat with 115hp suzuki made 40 knots........anything wrong?

Kernow Buoy · 28 October 2005, 08:44

Have a friend with a 6.5 Humber and a 140 Suzuki, top speed 38 kts.

rbw156 · 28 October 2005, 08:56

Solent 6.5 w/ 150 Merc Opti = 50 knots.

Mollers · 28 October 2005, 08:57

Those Suzy strokers are slow, heavy old girls. Better to ditch that for a proper engine. An Opti perhaps.

Rodan · 28 October 2005, 09:15

Humber 8m + 225 Opti - 38Kts too.... will be working on this as I would have thought more kts possible...

xpertski · 28 October 2005, 12:12

yeah traditionally the four strokes are heavy but the 140 is lihter than most, it weighs i think 186kg. maybe a different prop would help things. did actually consider an opti at the time, but had previously had a suzuki and thought it was an amazing engine, which the 140 i have is too, but, maybe could do with a bit more grunt!

Pete7 · 28 October 2005, 13:15

Quote:

Originally Posted by rbw156

Solent 6.5 w/ 150 Merc Opti = 50 knots.

Really ?

ADS · 28 October 2005, 13:21

Quote:

Originally Posted by rbw156

Solent 6.5 w/ 150 Merc Opti = 50 knots.

Is that 50 knots or 50 mph?

Nick Hearne · 28 October 2005, 13:25

Quote:

Originally Posted by Pete7

Really ?

With a 5 knot tide running

ADS · 28 October 2005, 13:32

Bruce seems to have had Farfetched at nearly 50 knots, but with Kevin from Solent driving:

http://www.rib.net/forum/showthread....ght=Farfetched

Pete7 · 28 October 2005, 13:36

The reason I ask is the best I managed from a Tohatsu 6.6m with 150 Opti was 55mph down southampton water on a very flat calm day with 19" inch prop. If you have managed to get a Solent which is similar but heavier lay up to do 57 mph thats some going, fast boat.

Xpertski, if it helps a 6.5m Ribtec with old type 150 Mariner did 38 knots. You could spend a lot of time testing to get the humber to go a little faster but would it be useable speed? or would the bigger prop, higher engine height etc mean that acceleration was compromised and make it a less enjoyable boat and what would happen when you put lots of people on board ?

Pete

rbw156 · 28 October 2005, 13:58

Yes, really, with about 20% full tank. Trim was spot on. Measured with GPS. Conditions were perfect. It is a fun and fast boat.

Pete7 · 28 October 2005, 14:05

There are almost enough of these Solents about to have a race series

rbw156 · 28 October 2005, 14:10

Perhaps a short one at 56 l/hr! However, normal cruise at 25 knots is 20 l/hr.

eupa · 28 October 2005, 14:45

well well...... give me my yams anyday!!!!!!!!!!!!!!! - although I would have preferred suks when re -engined in july.

I believe that the suk is slightlly more advanced than yams- but quite frankly dont know i thing about it. All I know is that i turn the key and they work-- and they run bloody well.

Jonathan

codprawn · 28 October 2005, 14:55

I am a bit concerned about how well a 19" pitch prop will push my boat along - it may be too fine for a heavy boat with 500 litres of fuel.

Am I right in thinking that a 19" 4 blade will behave more like a 21" 3 blade or doesn't it make much of a difference - also as I have a transom jack will loweing the prop in the water overcome the fine pitch?

eupa · 28 October 2005, 15:06

Quote:

Originally Posted by codprawn

I am a bit concerned about how well a 19" pitch prop will push my boat along - it may be too fine for a heavy boat with 500 litres of fuel.

Am I right in thinking that a 19" 4 blade will behave more like a 21" 3 blade or doesn't it make much of a difference - also as I have a transom jack will loweing the prop in the water overcome the fine pitch?

Sorry codders, on the second bit.. pass. On the first - its more trial and error and good trim. With the 225 go for a 23". On my 250 yams - the 25" gives 56.knts - but loosing 500 rpm. Johnny Fuller should advise you on this.
The 19" is probably not the right one for a 225... but its realy trial and error.

Jonathan

Alan · 28 October 2005, 15:34

Quote:

Originally Posted by Pete7

There are almost enough of these Solents about to have a race series

Can you say Tohatsu one design?

(although I suspect this is what you are alluding too Pete.)

Searider · 28 October 2005, 15:45

Quote:

Originally Posted by codprawn

I am a bit concerned about how well a 19" pitch prop will push my boat along - it may be too fine for a heavy boat with 500 litres of fuel.

Am I right in thinking that a 19" 4 blade will behave more like a 21" 3 blade or doesn't it make much of a difference - also as I have a transom jack will loweing the prop in the water overcome the fine pitch?

Pop it in the water and find out?

I'm sure the builders will be carrying out some trials and will try a couple of different props.

codprawn · 28 October 2005, 16:00

Quote:

Originally Posted by Searider

Pop it in the water and find out?

I'm sure the builders will be carrying out some trials and will try a couple of different props.

that is the only way - but I supplied the engine and prop - asked for a 21" but they sent a 19" - maybe I will keep that one for high speed light work and get another for when fully laden.