cobra 8.5 with a 225 opti

Hugh Jardon · 22 September 2005, 21:39

ok looking to change to a cobra 8.5 with a 225 opti, any of you experts out there know what sort of top end i can expect and what litres or galls per hours at the various revs and what mph or knots at the revs i can expect, ie 1000, 1500, 2000, 2500 etc

the thing is massive but the mrs likes it, will make sure i get nice white ropes for it

chris

gavin · 22 September 2005, 21:45

We can get .7 nm per litre on 7.4 with 440 ltr fuel tank with 225 opti, full chat 87 litres per hour

Mollers · 22 September 2005, 21:56

Hang on a minute! Did you actually buy the 7m with the 200 Opti? As for the other, Use it then fuel it. Why worry? As the Rolls Royce salesman always says " Sir, if you need to consider such things, should you be looking at a Rolls Royce?" Put £100 in mine after two days "pottering".

Hugh Jardon · 22 September 2005, 22:07

Quote:

Originally Posted by Mollulnan

Hang on a minute! Did you actually buy the 7m with the 200 Opti? As for the other, Use it then fuel it. Why worry? As the Rolls Royce salesman always says " Sir, if you need to consider such things, should you be looking at a Rolls Royce?" Put £100 in mine after two days "pottering".

unfortunatley agreed the sale then.....found out it was 4 years older than he had advertised it as, so decided not to go for that one, making a decision on another tomorrow, will advise.

just a panic pants here as i will use it quite a bit and wondering how much fuel i will use. and what is a reasonable cruising speed for fair fuel usage,
also
tried to update the profile to show buying a cobra but it does not have enough space for all that

but my heart is set on one.....unless someone can talk me into buying something similar, cheaper, nicer, faster and more economical with same sort of layout.

hard1 · 22 September 2005, 22:08

Hi Chris. As you know I've got an 8.5 Cobra Nautique with a 225 Opti, so maybe my figures will be of interest. I have a 21p Laser II. Clean, 2 up with 125 litres and flat seas - I get 42 knots @ 5100. If I pulled 5750 I would get over 50 knots.

As for consumption, loaded with 9 persons I get, on average a consumption of 2 litres per mile. Today, I blatted over to Yarmouth for lunch. WOT on the way over and 4K on the way back. I used approx 1.66 litres per mile 2 up with 125 litres on-board. If you are fairly conservative and keep revs @ 4K with a light load, I expect you will get 1.5 litres per mile average. Speed @ 4K is around 30 ish knots. Cobra 8.5 is not a particularly light build which is good, 'cos they're strong.

Hope this helps

Hugh Jardon · 22 September 2005, 22:13

Quote:

Originally Posted by hard1

Hi Chris. As you know I've got an 8.5 Cobra Nautique with a 225 Opti, so maybe my figures will be of interest. I have a 21p Laser II. Clean, 2 up with 125 litres and flat seas - I get 42 knots @ 5100. If I pulled 5750 I would get over 50 knots.

As for consumption, loaded with 9 persons I get, on average a consumption of 2 litres per mile. Today, I blatted over to Yarmouth for lunch. WOT on the way over and 4K on the way back. I used approx 1.8 litres per mile 2 up with 125 litres on-board. If you are fairly conservative and keep revs @ 4K with a light load, I expect you will get 1.75 litres per mile average. Cobra 8.5 is not a particularly light build which is good, 'cos they're strong.

Hope this helps

i was hoping you would see my post, cheers for this.....fecking thirsty and slow in my book, what am i getting myself into here, i dont know, but, you only live once.................
what speed is 2k, 3, 4, and 5, or is it all relative to the 42 at 5100?

Richard B · 22 September 2005, 22:16

Quote:

Originally Posted by hard1

I get 42 knots @ 5100. If I pulled 5750 I would get over 50 knots.

Less prop slip at higher revs?

Quote:

Originally Posted by Chris Hartley

slow

What sort of speed are you looking for? Speed costs...

Mollers · 22 September 2005, 22:19

Hell! a year out on discription is not uncommon, but four! The guy sounds like a robber. What year is the Ex- SAS 8.5m Cobra? Has the 30mm machine gun been removed? If the boat suits your needs and the missus likes it your half way there. I don't think that you'll hear too many neg comments on here about either the hull or the engine. Do your homework this time eh!

Hugh Jardon · 22 September 2005, 22:24

Quote:

Originally Posted by Mollulnan

Hell! a year out on discription is not uncommon, but four! The guy sounds like a robber. What year is the Ex- SAS 8.5m Cobra? Has the 30mm machine gun been removed? If the boat suits your needs and the missus likes it your half way there. I don't think that you'll hear too many neg comments on here about either the hull or the engine. Do your homework this time eh!

i did my homework on the thing and checked up on serial numbers with those nice folks at picton, very helpful, trouble is the 7.5 boat was a nice boat with a cracking engine but was not prepared topay the price for such an old hull.

actually it still has the 30 mm on the front and one on the rear and i wondered if you fancied coming out some time for some target practice....er....i mean fun?

hard1 · 22 September 2005, 22:29

Sorry 4k = 4,000 rpm. As you said, the 8.5 is a big boat and to be honest, 225 is just about the smallest you'd want to put on it. A 7.5 metre with a 200 is probably better pro rata. Any new 8.5 worth it's salt would have a 250, 275 or even 300 on it, but that's because they're 4 strokes. 42 knots slow? This is a 2 ton leisure RIB not a race boat. Believe me, in the average Solent chop, it's mostly quite enough.

As for "feckin' thirsty" my last 2 stroke was a 200 Suzuki that showed 120 litres per hour consumption at 5K rpm, 45 mph.

Any 2 stroke which produces 1.5 ish litres per mile is in some 4 stroke territory. If you want much better from a high horsepower combo, then consider a diesel inboard. Even if the Govt slash the concession on red diesel, they are generally more economical on fuel. But they come at a premium, say £5-£8K on the average equivalent length boat? Let me see, even at £1 per litre for gas that's up to 8,000 litres of gas which equates (even at 2 litres per mile) 4,000 miles of RIBing before a diesel makes more economic sense although the resale will always be better. You could even buy a new 250 Opti for around £8k with a couple of years warranty on it, as against £14K for the average 4 stroke and £18k for a decent diesel. You pays yer money and takes yer choice!

As for speeds at the other rpms, it is not at all relative to my 5100 rpm example. I'm on a charter tomorrow with a full load so that won't be exactly relevant either. The thing really doesn't get going until 4k rpm anyway.

Mollers · 22 September 2005, 22:31

Sounds good. A day out shooting Jetski

Can you eat 'em?

Hugh Jardon · 22 September 2005, 22:37

Quote:

Originally Posted by hard1

Sorry 4k = 4,000 rpm. As you said, the 8.5 is a big boat and to be honest, 225 is just about the smallest you'd want to put on it. A 7.5 metre with a 200 is probably better pro rata. Any new 8.5 worth it's salt would have a 250, 275 or even 300 on it, but that's because they're 4 strokes. 42 knots slow? This is a 2 ton leisure RIB not a race boat. Believe me, in the average Solent chop, it's mostly quite enough.

As for "feckin' thirsty" my last 2 stroke was a 200 Suzuki that showed 120 litres per hour consumption at 5K rpm, 45 mph.

Any 2 stroke which produces 1.5 ish litres per mile is in some 4 stroke territory. If you want much better from a high horsepower combo, then consider a diesel inboard. Even if the Govt slash the concession on red diesel, they are generally more economical on fuel. But they come at a premium, say £5-£8K on the average equivalent length boat? Let me see, even at £1 per litre for gas that's up to 8,000 litres of gas which equates (even at 2 litres per mile) 4,000 miles of RIBing before a diesel makes more economic sense although the resale will always be better. You could even buy a new 250 Opti for around £8k with a couple of years warranty on it, as against £14K for the average 4 stroke and £18k for a decent diesel. You pays yer money and takes yer choice!

cheers for this and i agree with all your points. i am a bit of a pain in the arse i know, i want comfort, quietness, speed, acceleration, economy, ride, smoothness, top end speed. I even went to the boat show looking for inspiration, looked at the various boats there and non caught my eye really compared to the cobra. well some sunseekers did but i could not even afford the mooring fees i suspect.

we went out today in the cobra 8.5 and my 2.5 yr old daughter was saying faster daddy faster and we were flat out!, mind you it was lovely and calm, might have been different if it was a bit choppy!!

IanE · 22 September 2005, 22:40

Quote:

Originally Posted by Mollulnan

Sounds good. A day out shooting Jetski

Can you eat 'em?

marinade in diesel,and boil slowly for 20 hrs... garnish with scottys splattered seagulls!!

Mollers · 22 September 2005, 22:44

The only thing that I can see against a Cobra is that most appear to have big soft bench seats which, when the going gets choppy are bloody hard to stay in. I prefer my Ribs a little more "Hard core" and would go for jockies every time. Especially at the helm.

hard1 · 22 September 2005, 22:45

Quote:

Originally Posted by Chris Hartley

mind you it was lovely and calm, might have been different if it was a bit choppy!!

Oh yes

But, the Cobra is one of the most stable and driest RIBS there is. It won't break speed records, but it will be there at the end.

Mollers · 22 September 2005, 22:46

Quote:

Originally Posted by IanE

marinade in diesel,and boil slowly for 20 hrs... garnish with scottys splattered seagulls!!

.....all served up in Noddy's helmet!

Sounds good.

Hugh Jardon · 22 September 2005, 22:50

Quote:

Originally Posted by Mollulnan

The only thing that I can see against a Cobra is that most appear to have big soft bench seats which, when the going gets choppy are bloody hard to stay in. I prefer my Ribs a little more "Hard core" and would go for jockies every time. Especially at the helm.

i looked at a few ribs that are probably a bit more hardcore at the boat show, not ready for one of those yet as we seem to like our comfort and seating area and dance area and sunbathing area. you did see my other post with the mrs idea of a rib and what she expects?

leaves me with little choice really! ;-)

Mollers · 22 September 2005, 22:51

Quote:

Originally Posted by hard1

Oh yes

But, the Cobra is one of the most stable and driest RIBS there is. It won't break speed records, but it will be there at the end.

50knts isn't too slow. There's not too many on this site that'll do much more than that. Mine wont

Richard B · 22 September 2005, 22:53

Quote:

Originally Posted by Mollulnan

...prefer my Ribs a little more "Hard core"...

Yep. Might as well get a dory otherwise

Mollers · 22 September 2005, 22:56

Quote:

Originally Posted by Chris Hartley

i looked at a few ribs that are probably a bit more hardcore at the boat show, not ready for one of those yet as we seem to like our comfort and seating area and dance area and sunbathing area. you did see my other post with the mrs idea of a rib and what she expects?

leaves me with little choice really! ;-)

Yeah, I've had yank hardboats pre the Rib. I do think that a nice Searay 21ft sports cuddy would suit her perhaps more than a Rib

! Warmer, more comfortable and with creature comforts. Fast too. Just a thought. I had one for nine years and had the best times with it. The kids grew up with it.