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Old 12 June 2014, 14:15   #41
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Yep, cheers, will probably leave it as it is with height as per pic and standard prop - it picks up really well and 18 kts is fine really.

Not had my tiny tach on it yet to check WOT RPM but will soon.
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Old 12 June 2014, 21:02   #42
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Hey Max.

Forgot to ask you, told that on your small standard sib, dialing lower WDP against water flow (Sweet Height Spot) worked very good. Was wondering when outing by yourself on flat calm no wind water. If going full grip to plane faster the bow will rise accordingly, do you need to move yourself forward for bow to come faster down ? Or bow eventually will come down annyway but will take bit longer without in the need to move yourself forward. Which one applies or both does ?

Don't play with props or prop pitches by suggestion without a induction tach, very bad musique for your engine. That's what tachs are, to measure max wot rpm factory stated for that engine..

PD, still writting my assay as homework..

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Old 13 June 2014, 02:47   #43
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Loco, wasn't quite sure what you mean but my normal loading is me, one child and (like all SIBs they need some load up front to make them less 'bow happy') a Pelicase with anchor and gear midships. Boat pops up on the plane very nicely and bow drops quickly.
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Old 13 June 2014, 11:26   #44
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General question : Let's say that on a dry installation at your house, you have dialed a perfect AV plate even or slight lower than keel/boat's bottom.

-What do you expect your sib to achieve ?

-Did you take into account that water flow will pass under lower tail when sib is on plane at speed. Yes, No.

-Not even considered it ? Short answers please.

Max, was asking because on my previus 360-380 sibs with engine perfectly height seated didn't need move myself forwward or place weight up front, just went full throttle, bow whent happily up and in 3 seconds literally jumped on plane, that was with a 18 HP, both sibs rated for 20 HP.

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Old 13 June 2014, 14:34   #45
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Quote:
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Goodness knows why Bombard don't change the transom shape with a shallower cut out on top so we dont't need to comprimise like this with raiser blocks, too costly for them I guess in tooling or whatever.
I completely agree with you. There's something wrong with this whole industry.

Imagine that when you bought a car, you had to buy tires and you had to trial different types and treads and widths to get you car to just run properly. Imagine that you had to modify the suspension just to get the car to run properly with a particular tire. I'm not even talking about milking every last drop of performance out of it - just to get it to run properly.

The transom length on my boat was 18 inches and the shaft length on my outboard was 22 inches. Why couldn't they both just be 20 inches?

I had to have my transom plated to raise the motor 2.5 inches. Without that major modification to my transom, the twisty clamps that fasten the motor to the transom would have been above the transom on 2,5 inch lifting blocks.

One should be able to get their boat to run well or at least reasonably well by just dropping an outboard on the transom and going.
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Old 13 June 2014, 18:53   #46
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I suspect they have their reasons still somewhat puzzling.
My boat is under-powered for sure running 25 hp while rated for 40 but performs reasonably well.

Still planes perfectly well with 3 adults and 3 kids on board. Tops out at about 18-19 knots under that load.
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Old 14 June 2014, 12:24   #47
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FC470s are great boats. The futura hull really helps with getting the boat to perform better with less power. I love your boat. How did you find and get it?
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Old 14 June 2014, 12:25   #48
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Does anybody have personal experience with how much difference a stainless steel prop makes vs aluminum? I'm particularly interested in how much, if at all, it reduces cavitation on turns... and any other differences you think SS really makes.
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Old 14 June 2014, 12:26   #49
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Can anybody recommend a good iPhone app for measuring boat speed?
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Old 14 June 2014, 20:45   #50
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Quote:
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The transom length on my boat was 18 inches and the shaft length on my outboard was 22 inches. Why couldn't they both just be 20 inches?

One should be able to get their boat to run well or at least reasonably well by just dropping an outboard on the transom and going.
Are you using a short or long shaft engine on a 18 inch transom ? If a short, its too short, probably water flow at fast speed/plane will pass skimming around AV plate, if so will have prop ventilation on choppy seas and at close turns.

As you have experienced, a boat/engine is not a car. It's not a matter of just droppimg engine on transom and voilá, in most cases will need to fine tune engine height for top performance. When sitting any engine need to have 3 important issues into : transom height, engine brand and very important tube's diameter.

That's why is irrelevant on sibs AV plate distance on a dry installation at home becuse you don't know how much or less sib will float once on water. As a enecdote, we installed 2 new 18 S Tohatsu on 2 diffrent lenght sibs. On the 380 experienced excesive water splash over transom, 420 worked perfect, why was that so ?

Very simple, 380 had 38 cm transom height and 45 diam tubes, 420 had 38.5 transom height and 50 diam tubes. The 420 floated much higher than the 380, had to raise 380 transom 2 cm to perfom exact same as the 420. The wider 420 diam tubes compensated having a shorter transom height compared to a higher one on the 380.

Happy Boating
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