Suzuki 300 prop advice needed

[Flavio]

Hi,

I am running a Suzuki DF300 on a Zar 65 RIB. I am overpropped, maximum rpm's are 5500 @ 56mph. With a gear ratio of 2.08 this calculates to 3% propslip, which is very good. Current prop is 3x16x23P.

I want to get the most speed out of this combo so I want the engine to run to its maximum of 6300rpm.

What effect would a smaller diameter prop have on rpm? I can get a 14 3/4x23 or 14 3/4x21 prop from Suzuki.

I don't want to go down too much in pitch because I want to reach 62mph (100kph) which is 4.5% propslip with a 23" pitch prop @ 6300rpm.

Will the Suzuki 300 take standard Mercury or Yamaha props because then I would have a much broader 3rd party choice of props above the limited Suzuki prop range.

Before anyone asks, the Zar 65 is rated for maximum 200hp but absolutely does not feel overpowered with the Suzuki 300! The reason I wanted the 300 is the fly by wire controls and I got a good deal on the Suzuki 250 which was on the boat when I bought it.

[2012Marine]

Flavio,
at 6300 you will be maxed out and i would council against making this your target the WOT operating range is 5700 - 6300, this is the band I'm in at the moment WOT on my boat 5.8 / 9 ish I'm running a 4/16/20.

Incidentally I have a 4/16/21.5 you could try this on it. I would think you would be hitting around the 5.9 mark with this.
Other factors will have an effect, engine height on transome, load in the boat, sea state etc etc.

Cheers

Greg

[Flavio]

Originally Posted by 2012Marine

Flavio,
at 6300 you will be maxed out and i would council against making this your target the WOT operating range is 5700 - 6300, this is the band I'm in at the moment WOT on my boat 5.8 / 9 ish I'm running a 4/16/20.

Incidentally I have a 4/16/21.5 you could try this on it. I would think you would be hitting around the 5.9 mark with this.
Other factors will have an effect, engine height on transome, load in the boat, sea state etc etc.

Cheers

Greg

The 5500 rpm is fully trimmed out and at maximum height (hydraulic lift) and with light load (1 person). 6300 rpm is within the Suzuki specs so why shouldn't I use it as a light load target?

[codprawn]

To be totally accurate you need to see a torque and bhp curve for the engine. I very much doubt the peak is developed at maximum revs - it's usually somewhere between the 2 figures.

[Mollers]

Hang on a minute, you're 100hp over the max design hp?! The reason it's plated at 200hp is not just because of transom weight. The hull design and everything about that boat is now thrown out of kilter. You might start to get some pretty irratic handling as you pile on the knots. Insurance must be a bit of an issue also.

[codprawn]

Originally Posted by Mollers

Hang on a minute, you're 100hp over the max design hp?! The reason it's plated at 200hp is not just because of transom weight. The hull design and everything about that boat is now thrown out of kilter. You might start to get some pretty irratic handling as you pile on the knots. Insurance must be a bit of an issue also.

He doesn't live in nanny UK!!!

[Mollers]

Originally Posted by codprawn

He doesn't live in nanny UK!!!

No, but his kids might need a nanny after he's flung himself out of the thing.

[Mollers]

[QUOTE=Flavio;208917] Hi,

I am running a Suzuki DF300 on a Zar 65 RIB.

Is it the Zar 65 (3 piece) Suite model?

[Ezgoing]

Flavio

I have the Suzuki 300 and am very happy with it. There have been cavitation and ventilation problems with many of them. It is not the fault of the engines. This is because of the amount of torque being delivered (unbelieveble) and the fact that they are so new and the manafacturers are having to test out various settings and prop types to work out what goes best with the various boat options being offered.

In my case it has taken three props and much effort from Suzuki, Redbay and Steel Developments. Given that my boat is a completely new configuration and that the engine is so new I do not think this is unreasonable. Gladly all now arrears to be in order.

Prop choice is four blade from Steel Developments. Julie has worked with a number of people to get it correct. Engine is maxing out at 6000rpm and I agree with earlier suggestions about max revs.

best of luck

[Flavio]

Thanks for all the comments. I'm a big boy and if I want to put 300hp on a 200hp rated boat it's my decision.

Unfortunately no one has answered my question what effect on rpm a smaller diameter prop would have. There must be some rule of thumb for this just as there is for going up or down in pitch?

I tested the boat again today and apart from some mild chine walking at maximum trim the boat feels absolutely safe at any speed.

BTW It is the 65 Suite model.

[Mollers]

Originally Posted by Flavio

I'm a big boy and if I want to put 300hp on a 200hp rated boat it's my decision.

You must be a very big boy!

[codprawn]

Well obviously the smaller the prop diameter goes the higher the RPM. 4 strokes tend to provide more thrust at lower RPM which is why they tend to have bigger diameter props.

Obviously a larger diameter prop will provide more drag so to go faster it's smaller diameter bigger pitch you need.

[IBWET]

Originally Posted by Flavio

Thanks for all the comments. I'm a big boy and if I want to put 300hp on a 200hp rated boat it's my decision.

Unfortunately no one has answered my question what effect on rpm a smaller diameter prop would have. There must be some rule of thumb for this just as there is for going up or down in pitch?

I tested the boat again today and apart from some mild chine walking at maximum trim the boat feels absolutely safe at any speed.

BTW It is the 65 Suite model.

Your not a little overpowered you 50% overpowered which is enormous I would be inclined to ask the manufacturer of the boat after explaining your experience to them why it's rated at 200. There may be a very good reason we all here haven't touched on, better to know before you do a tripple salco with half turn out the thing as mollers says.

If the boats handling the power easily I think the prop you've got must be crap if you go down in diameter the (and I could be wrong here,but it's my experience) the slip will increase and you gain nothing. I have a similar problem and have gone down the hydromotive 4 blader route. I'll post results when I have them.

[codprawn]

It could be the 300s weren't around when the boat was designed - also most companies err on the side of caution these days. Remember the 300 weighs not much more than a 200 and less than a Verado 200 straight 6!!!

[searafting.no]

If you want realy go fast props try 25" Mercury revelution 4 prop with Suzuki hub or a Mercury bravo one with Suzuki hub, the revelution 4 is faster than than the Bravo one, you could get the revelution 4 up to 25" pitch.