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Old 29 June 2020, 04:34   #1
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Suzuki DT100 prop size and pitch.

Is there just one prop for this or can I change to different ones for better performance etc. Any advice would be appreciated.
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Old 29 June 2020, 05:15   #2
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Boat name: Sula
Make: Ribcraft 4.8m
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Engine: Tohatsu 60hp + aux
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Welcome to the forum.

You need to explain a little more as to what you're trying to achieve. I'm no Osprey expert, but on a 6m RIB, I'd have thought you're under-powered for starters, so yes changing the prop pitch will help, but all things being relative it's not going to overwhelmingly change the situation.

How many people on board normally, fuel capacity and any other things to take into account weight-wise. You need the tacho and maximum WOT for this engine before you start changing props to see how much wiggle room you have.

For your engine it's 5,250-5750 rpm.
https://www.rubexprops.com/boat-prop...e/?make=Suzuki
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Old 29 June 2020, 06:52   #3
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Hiya bud
Thanks for your reply
This is about a rib I have just acquired.
Iíve had fishing boats but first time on a rib. From what I can gather the max size is 115hp for this particular one. Iím going to run this 100 for the time being and see how she is. Also read somewhere that they may have uprated it to a 150 so need to do a little more homework on this. The prop is goosed and needs replacing at the moment. I looked for one and itís a bit of a minefield. Ally / stainless
Pitch etc.
The chart helps a lot
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Old 29 June 2020, 06:53   #4
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There will be around 2 to 3 ppl on board.
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Old 29 June 2020, 12:19   #5
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Country: UK - Scotland
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The transom rating is based on the manufacturer's assessment of an engine's weight and overall speed range of the hull at the time it was built. Key-thing is not to exceed it which theoretically could invalidate your insurance.

My understanding is the DT100 is around 150kg. Depending on the actual transom rating you may be able to change it to 115hp if that's what the plate allows. Hopefully Osprey owners can confirm their experience of this, given the DT100 is an old engine now.

Back to propellers. Aluminium are great all-rounders. There's a misconception that going to stainless is going to reap huge performance benefits. Yes, on larger engines they do have the benefit with a stiffer blade construction if won't flex at WOT, and should fair better long-term. Drawback with stainless, is if you hit something that power isn't absorbed by the propeller and can result in stripping gears or even the splined drive shaft. Aluminium, then you're likely to bend the blades on any impact and save the gear-box, and in real terms they are fairly cost effective to replace or repair.

You'll probably need to remove the propeller to see what's on it just now (there will be marks on the back of the blade or potentially inside the hub). Lowering the pitch, can improve hole-shot at the expense of overall speed, however it will allow the engine to reach maximum rpm at slower speeds.

Key thing - is what's the boat achieving just now in terms of rpm at full-throttle, trimmed, etc. And what's your aim, increasing speed or hole-shot from a standing start?
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Old 30 June 2020, 03:19   #6
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Thanks
Iíll be picking the boat up in the next couple of days. Iíll get right into all this once in my yard. Itís going to be getting stripped down for a good going over. I was looking at an old thread and apparently at some point they uprated the engine size so it depends on what year etc it was manufactured. Apparently there is no plate on the transom but there is other ways to classify the age.
I had a chance at an evenrude150 which weighs in just a few more pounds than the old 100dt. But thereís that too much power thing to consider carefully.
Think Iím getting a little too enthusiastic and excited before Iíve even picked it up. Your input is greatly appreciated tho. Learnt a lot already
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Old 13 July 2020, 13:40   #7
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Make: Osprey - Eagle 5.6m
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Hi,

I run my Eagle/DT100 on a 17Ē prop. With four divers plus one she happy at 25-28knots.

These are the props as quoted in the workshop manual.

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Cheers,
Gadge
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Old 17 July 2020, 08:47   #8
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Cheers gadge thatís good info. Nice to know someone has the same set up too. First rib for me so be prepared for a million questions
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