how fast is your rib?

[Xk59D]

You have the wrong props there by looks of it, I wouldn't run the 5400rpm prop at all and 6150 must be close to banging off the limiter, looks like you need to find a middle ground ideally, reworking the smaller prop would probably do it if you sent it out to have pitch adjusted to get you in the 5900 ish range, be ideal.

I think my 200df has the original Suzuki 20" pitch and flat out trimmed out it will just about touch 6000rpm with my normal loads.

My 6.8 ribcraft I know fact is 1610kg with 200 litres of juice with no passengers and 25mph is 23lph, 28mph is 26lph, I don't bother looking at the rest really but seems reasonable to me.

[AndyFresh]

Thanks Xk59D
Good info. Your boat is a wee bit heavier than me hence the difrent numbers but in the same ball park which is good to know.

Hull700kgs
Engine 265kgs
Fuel 160kgs
2 bods 140kgs
Junk 35kgs
Total 1300kgs rough guess!


The boat came with a 20 inch power tech prop. Previous guys was all tooled up for diving i think. Always running a bit heavier than i will likely run hence the new 22.

Yes now that i have bought a 22 it seems obvious i should have bought a 21.5 from suzuki or a 21 from powertech.....

Nobody in the world or at least in France Switz US or UK where i looked was prepared to let you try before you buy as far as i could see. Would have liked to try a couple others before dropping £600 on my guesswork!

Just out of interest why do you think 5900 is the right wot figure. I thought the operating range for this engine was 5000 to 6000 meaning both props are within engine parameters?

Am i missing something

Thanks for your info. Looking forward to a blast round mull in July in mates 6.7m Ribcraft that was also on the short list! Just couldnt find one in the time frame and price!

Love this old engine though. Bit of an upgrade from the optimax

Cheers

[Xk59D]

The only major problem you ever see (and I've had it briefly) is when the engine can't rev out and subsequently makes oil due to lack of load/heat.

I'm fairly certain that a slow day at loch lomond gave me the issue but I had to rev the nuts of it so to speak for a while and problem solved, it was in warranty so I just done what Suzuki told me.

Anyways, given my conversation with Suzuki UK and the dealer I always aim for getting damn close to the max rpm to avoid the above again.

're the weight of the boat, mines was via weight bridge and taking trailer weight off (I weighed that separately on another occasion to make sure I bought right trailer)

[AndyFresh]

Yep a handy weigh bridge would be really good.
I weighed the old boat at whitness sands on the inverness nairn road. You could go in to jf jobs sand quarry and the lad would let you do a quick measure.
Unfortunately boat is now out on Lac Leman. ....
Not really on my way home any more

Thanks for the advice!

Andy

[breezeblock]

Originally Posted by Xk59D

The only major problem you ever see (and I've had it briefly) is when the engine can't rev out and subsequently makes oil due to lack of load/heat.

I'm fairly certain that a slow day at loch lomond gave me the issue but I had to rev the nuts of it so to speak for a while and problem solved, it was in warranty so I just done what Suzuki told me.

Anyways, given my conversation with Suzuki UK and the dealer I always aim for getting damn close to the max rpm to avoid the above again.

're the weight of the boat, mines was via weight bridge and taking trailer weight off (I weighed that separately on another occasion to make sure I bought right trailer)

I think it was overfilled oil isn't magic and doesn't self produce if it was fuel a simple oil sample would have confirmed

[Xk59D]

Well as you know I didn't do anything except take it to dealer and talk to Suzuki. No oil sample was taken by me and Suzuki didn't ask me or dealer to get one until we confirmed if it happened again.

However, that doesn't change fact making oil is not unheard of with 4 strokes and the makers normally start with prop choice, not reaching max rpm is always a get out for them.

On a side note the dealer doesn't fill to max anymore as per Suzuki advice. Just slightly under it now. Funnily enough, if you fill my volvo xc90 oil up to max the engine management light comes on.....POS

[breezeblock]

Originally Posted by Xk59D

Well as you know I didn't do anything except take it to dealer and talk to Suzuki. No oil sample was taken by me and Suzuki didn't ask me or dealer to get one until we confirmed if it happened again.

However, that doesn't change fact making oil is not unheard of with 4 strokes and the makers normally start with prop choice, not reaching max rpm is always a get out for them.

to make oil neat fuel would have to dilute the oil this you would have fouled plugs from excessive rich mixture it doesn't stack up as said an oil sample would have been such an easy test to confirm either way an saved a whole lot of farting about

[Xk59D]

Farting about? Phone call, take boat to dealer, keep eye on it...under warranty so not my problem

[ribraff]

Demon 650 Huracan-175 Opti-19” Stainless 47kts

[gpsguru]

Originally Posted by Xk59D

The only major problem you ever see (and I've had it briefly) is when the engine can't rev out and subsequently makes oil due to lack of load/heat.

I'm fairly certain that a slow day at loch lomond gave me the issue but I had to rev the nuts of it so to speak for a while and problem solved, it was in warranty so I just done what Suzuki told me.

Anyways, given my conversation with Suzuki UK and the dealer I always aim for getting damn close to the max rpm to avoid the above again.

're the weight of the boat, mines was via weight bridge and taking trailer weight off (I weighed that separately on another occasion to make sure I bought right trailer)

As has been said, oil cannot self multiply and if it was neat fuel in the oil the engine would have run like a 'bag of poo' .............. however, you may have had a rare occacsion of oil foaming, which gives all the symptoms of way too much oil in the sump and can often be accompanied by blue smoke as the 'foam' is easily moved around the engine with the main body of oil. We get this from time to time on a couple of V8 race car engines that I look after ........... the answer is in the characteristic of the oil being used and the design of the engine lubrication system, better sump baffles seem to be the way forward, but in your case you are stuck with what 'zuk' have given you.



Often oil foaming can be cleared by putting the engine under load for a while, but the initial exhaust smoke can be more then a little worrying ......

[xchsurfers]

I manage to get 55.4mph on the Garmin from my ribcraft 585 with 150 optimax running on a 19" std prop. Steady as a rock Brillant alrounder boat

[mavrick211]

i got a zodiac Hurricane 590 with 150 etech i can do 45 with me and my buddy full tank of fuel trimmed out. gets touchy though i like 35 better

[mhb100]

Originally Posted by mavrick211

i got a zodiac Hurricane 590 with 150 etech i can do 45 with me and my buddy full tank of fuel trimmed out. gets touchy though i like 35 better

Ballistic 7.2m with yam 250 HPDI 50 knots with a fair bit of kit and a few people on a flat day. Nice to do the odd blast but we tend to cruise the boat at 25 to around 35knts. Don't need anything faster.

[holtz]

Zodiac SRMN 600 with an 1997 Yamaha 115 2-stoke goes 40 knots with a full tank and two grownups (2 x 110 kg)

[mavrick211]

I believe most boats have a hull speed and if you have a deep V like mine my hull speed is lower

[ShinyShoe]

Originally Posted by mavrick211

I believe most boats have a hull speed and if you have a deep V like mine my hull speed is lower

Hull speed only applies to displacement speed. Never heard that depth of the V affects hill speed...
The calculation is:

1.34 x √LWL

LWL = waterline length in feet
Result is knots...

You'll find a number less than 10 for most RIBs... but most RIBs will have top speeds >20knots on the plane.

[diaster]

Originally Posted by ribfan

In calm water, my 21' Ribcraft, powered by a 150 hp honda, tops of at 43 knots, or 49.5 mph. At the speed you were at, it sounds like the boat was chine walking, which can be pretty scarey. There are a number of threads in the rib forums on chine walking.

Bill

Eclectic Wonders uncommon art

What prop are you using?

[diaster]

Originally Posted by JA1000

20 ft with Yamaha 150hp - 41knts on 1st sea trial in slight chop, 2 up, engineer on test with me said has a little bit more left but then...

Since a Bimini installation plus 200 litres of fuel and 30 litres of water 38/39 is the limit.

what prop specs do you havplease?

[diaster]

Originally Posted by Ribdude

is anyone running a 150hp or 175hp outboard on a 18-20ft RIB?

I am running a 150 yamaha on my pro open 650.. 21.5 footer

[diaster]

Originally Posted by tworotorturbo

I did a BF150 on a 20' Searider. She went 53+ mph.

prop?