what speed should my rib achieve?

[Pete7]

Originally Posted by Alan

Can you say Tohatsu one design? (although I suspect this is what you are alluding too Pete.)

I wouldn't dream of drawing the readers eye to the similarities of Tohatsus and Solents, (although I suspect this is what you are alluding too Alan)

Codders, with the Solent and a 150 Opti its a known boat and engine option and indeed the Scorpion isn't that disimilar (howls of protest from Scorp owners) but yours is a completely different size to most ribs on here and big Suzukis engines aren't that common. Perhaps Jason could avise you but make an allowance for any differences in gearbox ratios if he quotes figures for a large Opti for example.

Pete

[archie720]

have found it very difficult to get accurate speed readings in s'ton water or the solent as tides are so strong. when looking for records even half a knot of tide can make a difference to your best ever speed! ideally need to go to s'ton water on a flat calm and wait until slack water then get a gps reading going both ways and take the average.

also watch out for people confusing knots with mph as people can be very quick to "accidently" make the mistake of saying their boat can do 50 knots when actually its only 50mph!

as a bench mark our 6.3 m with a 115 optimax and 20pitch s/s prop has a record of 45.2 knots or 52 mph although i imagine there is a knot or two of tide in that! Am taking it to the med next summer so with no tide will get a much better indication although then you get into all the complications of what is the best air temp and humidity to run an engine at...

[Alan]

Originally Posted by Pete7

I wouldn't dream of drawing the readers eye to the similarities of Tohatsus and Solents, (although I suspect this is what you are alluding too Alan)

Test drove the 6m Prototype/Demo with Tohatsu 90 back in ohh 98 I'd say. Shame the one design class didnt work out, we thought about buying one and entering. In hindsight, glad we didnt. (Although we did buy a BWM instead )

Originally Posted by Codprawn

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.

Errrmm you asked for a 21" pitch, got a 19" and you think that the 19" might be too high a pitch for laden work? Begs the question as to why you asked for a 21" in the first place? Given the 'unique' nature of your RIB. (Old tech engine, monster jackplate, other Codccesories) I suggest you stick the 19" on and see how it goes before investing in anything else.

[Alex Brown]

Originally Posted by xpertski

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?

What revs are you attaining at 39knots? - if you're running over 5800revs, then changing prop won't gain you any more speed. If it's under that band, that's below the max output of the engine so maybe a change to 20 or 19" may be in order.

I remember that Practical Boat Owner article on the 115 Suzuki with 6.3 Ocean Pro - I think they must have had a strong following wind and been stuck in a decent tide.

At 39knots, is your engine trimmed up as high as it will go? - for me to get over 40knots, the engine has to be right on the limit of going into shallow drive cos the transom on the Humber is quite steep.

My max on the humber destroyer is only just a smidge over 40knots - last Sunday we didn't even get that high cos of the wind.

-Alex

[codprawn]

[QUOTE=Alan]
Errrmm you asked for a 21" pitch, got a 19" and you think that the 19" might be too high a pitch for laden work? Begs the question as to why you asked for a 21" in the first place? Given the 'unique' nature of your RIB. (Old tech engine, monster jackplate, other Codccesories) I suggest you stick the 19" on and see how it goes before investing in anything else. [/QUOTE

Whoops other way round!!!

It may be an "old tech" engine but it is probably the lightest 225 leisure engine on the market - and not that old tech - 2 plugs per cylinder - efi and fancy ceramic pistons with boron liners.

Doubt it will compare with an Etec or Optimax on economy though!!!

[Matt]

Thank goodness!! A voice of sanity.

Originally Posted by archie720

have found it very difficult to get accurate speed readings in s'ton water or the solent as tides are so strong. when looking for records even half a knot of tide can make a difference to your best ever speed! ideally need to go to s'ton water on a flat calm and wait until slack water then get a gps reading going both ways and take the average.

[Nasher]

Have to stand by Codprawn on this one.

I've always liked Suzukis, and always prefered 2-strokes, and that 225EFI is, in my very humble opinion, one of the best engines ever made.

My poor mans second best is the late 90's 200EFI I run, and it would get swapped for the newer 225 anyday I could afford it.

Their power to weight ratio is so good, and the technology relativley straightforward. My 200 will cruise my 6.5 Ocean at 25-30 Knots on about 1.2 l per mile, not terrible by any means. It'll also top 50 Knots in the right conditions. Like any secondhand engine it's had its faults, but thats due to not being looked after by the previous owner rather than the engines fault.

Also have to say that calculating props etc is not an exact science, I spent a lot of money on secondhand props following advise from calculator wielding experts when I tried to get the best out of my old 150VRO that was on the Ocean when I brought it, the prop I ended up with was way off what I was advised to use. Then when the Suzi was on the boat and I published some stats, I had several replies questioning what I was seeing on my own boat, because their calculators didn't agree!

Not often I post these days, but needed to say the above, Its about time somebody agreed with something Codprawn said, rather than take every chance to have a go.

Nasher

[ADS]

Have to say I can't fault my 'old tech' Suzy two stroke, often simple is best, I don't need all this electronic gadgetry if i want to fix and service it myself. Im with Nasher and Codders.

Nothing wrong with Suzukis Hensh, see comment in Nasher's engine thread. Im loving your website by the way £6k for a 2003 Valiant 340!!!!

http://www.nationala1marine.co.uk/se...bs_forsale.htm

[biff]

I am running a 6.3 with a evinrude 175 fantastic excelaration,top end could be better 40kts . any tips

[xpertski]

What revs are you attaining at 39knots?

the revs would have been close to max, cant remember the exact number when speed was topped, but i would suspect not too far from 5800 revs. i think the max revs on the suz 140 is 6000 revs. however the ocean pro has quite a deep vee hull, so i guess not as quick as some other ribs


At 39knots, is your engine trimmed up as high as it will go? it is trimmed up most of the way, just to sneak the extra knot, but i guess i could try tilt it to the max limit....wow the 40 knot barrier is a tough one to crack!