ABC Sib-Rib Installation Guidelines.-

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

That boat has speed tubes and is not what his instructions were meant for. It agrees with his discussion anyway, believe it or not. So what is your point of misunderstanding?
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

What do they have to do with motor mounting? Instruction seem to imply applicability to any kind of boat (SIB-RIB) as they speak about generic water flows around motor/gear-case housing. Seariders's RIB has considerable V do they apply to flat bottom inflatables then? How and why? Why not Futura hull then?
Speed tubes add to stability and seaworthiness of boat.

Give me any rational reason why for general performance it's better to drag more gear case through water than necessary? It's like adding parachute to your car and claiming it will go faster and save fuel to be brutally honest.
 

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

Did you actually read his postings?
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

I did. Most of it decent info except motor height in regards to transom bottom. Did you read what I posted? It's a tall order to go against entire industry. When picking up spares at The Inflatable Boat Center very reputable local shop I spoke with techs. They are certified mil-pro shop that been around for years let alone sold/rigged up hundreds of inflatables of all kinds. They unequivocally said: anti-cavitation (ventilation whatever) plate must be level or just below transom bottom. Futura hull or not doesn't matter.
 

Sea Rider

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General Clarification.-

General Clarification.-

Sibrider,

To start with, you haven’t read the entire post throughout fully, have been stepping stone through the topics, all of which are technically related to each other.-

As stated since the very beginning, the post is only applicable to standard sibs and ribs bearing Tohatsu engines which most Tohatsu boaters knows are prone to experiment unwanted water splashes and bad behavior mostly due to their lower legs shapes issues if not correctly height seated.-

Have stated clearly at bottom of post that don't work with deep V inflatable decks nor sibs that uses speed tubes, mainly because I work with just sib/ribs and Tohatsu engines all of which can be seen here : Sea Rider Boats/Tohatsu Photo Gallery by Luis Montero at pbase.com

All sibs/ribs shown have been factory transom height modified to perfectly match Tohatsu engines, the post corresponds to the tests done to different sib/rib under trial and error on a ideal rowing track with no wind flat glassy water course. No ideal AV plate "cast on stone" heights 1” to 2.5” stated on all engine’s owner manual were taken into consideration as I like to sit lower leg much diferently.-

As mentioned before, you need as a first starter to sit your engine brand at any given sib/rib transom delivered height, go for a wot spin and check if already you happen to have matched the sweet leg/transom height spot or experiencing frustrating out or over water splashes or aeration problems at back transom.-

You have ventured to give very imprecise, exaggerated & contentious personal theoretical poinst of view that will prove not applicable with tech facts, yours is plain Mars Theory : So the only point you haven’t got clear so far is with respect to leg height and drag. You quoted saying the following : Give me any rational reason why for general performance it's better to drag more gear case through water than necessary? It's like adding parachute to your car and claiming it will go faster and save fuel to be brutally honest.-

Nobody is dragging gear case more on water at wot, you have not taken into the least account that all engines have a sharp front angle of attack that usually measures 3” in height where water flow at speed is perfectly and immaculate cut as a cheese there, then it’s smooth-out against perfectly torpedo rounded gear case housing and out to wake.-

If you lower leg for flow to skim above upper water deflector plate will have splash issues and increment leg drag, on the contrary, if you raise leg for flow to skim above AV plate, will lose best prop thrust and experiment prop aeration issues at choppy water conditions and at close turns, both cases at speed.-

A sib with speed tubes has a completely different behavior than a standard sib/rib, you already know that, can't be placed on same sack, don't understand why you like mixing mangos with prunes, Milpo to non Milpo sibs, Suzuki to Tohatsu engines, having all different water performances between them. Sibrider, do yourself a big favor, ask Suzuki or Zodiac Milpo tech dept to help you out to solve your sib/engine combo own tech flaws to quit contaminating this tread with post, pics and untested tech facts that do NOT APPLY.-

The overall idea of the whole post was to optimize max rpm up to 50 HP engines delivered with factory standard props, to obtain best prop thrust, impeccable close turns at speed at any water condition, optimize fuel consumption by needing to throtle less if boating with a sib or rib. On flat glassy waters both cruising behaviors are exact same as long sib's tubes and keel are inflated to max factory recommended working psi with gauge to achieve opt slide with least hull drag.-

Fbpooler, thanks for your kind tread support, but due to human nature, you will always find people that don't like seeing farther than their nose…

Happy Boating
 
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SIBRider

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Re: General Clarification.-

Re: General Clarification.-

Sibrider,

As stated since the very beginning, the post is only applicable to standard sibs and ribs bearing Tohatsu engines which most Tohatsu boaters knows are prone to experiment unwanted water splashes and bad behavior mostly due to their lower legs shapes issues if not correctly height seated.-
Searider, your post implied general guidelines for proper installation of motors on SIB-RIBs. I've read it and honestly disagree with some aspects of it. Hence posted my comments. Yes my boat has Futura Hull, and Suzuki not Tohatsu motor. Yet using your own words
Sea Rider said:
these guidelines will solely and exclusively shall be applied to all OB?s brands up to max 50 HP, tiller driven, with mechanical trim, tilt and handle clamp screw. Although full concepts are quite applicable to all outboard boats in general.
How else it can be understood but being applicable to all brands?
Then
Have stated clearly at bottom of post that don't work with deep V inflatable decks nor sibs that uses speed tubes, mainly because I work with just sib/ribs and Tohatsu engines
Yete you indicated belief that they apply across the board:
Haven?t had the opportunity to test Inflatable deep V decks nor speed tubes sibs mainly because don?t work with them, both have their own flaws compared to traditional sib/rib own flaws, but I?m sure all of what been written here could be applied to them,
Actually it is true that generally mounting guidelines are pretty much universal.
No ideal AV plate "cast on stone" heights 1? to 2.5? stated on all engine?s owner manual were taken into consideration.-
Where have you seen this? Certainly not in my posts. General guideline are as I said earlier AV-AC plate being 0 to 1" below keel at transom.
You have ventured to given very imprecise , exaggerated & contentious personal point of view that will prove not applicable with tech facts, not plain Mars Theory of yours :
...
Nobody is dragging gear case more on water at wot, you have not taken into the least account that all engines have a sharp front angle of attack that usually measures 3? in height where water flow at speed is perfectly and immaculate cut as a cheese there, then it?s smooth-out against perfectly torpedo rounded gear case housing and out to wake.-
Your cheese get harder as you speed up. At slow plane it might be Brie but once you get to 40 mph it's more like Parmesan. It's always easier to cut narrow slices. As you propose to have water pass just under deflector plate you are dragging extra 2-3" of gear case through water.

How you came up to this conclusion not exactly clear to me either. I believe that you so what you so but it just doesn't quite compute.
Pic-2 With water flow passing slightly under deflector plate achieved + 1 knot and 200 revs more than passing slightly above AV plate. Having more water to work with the prop grips much better.-
How is it possible that under increased load (resistance/grip) your RPMs increase? If anything prop positioned too high will cavitate/aerate consequently leading to uncontrolled increase in RPM resulting in over-revving motor. Yes that might result in drop in speed because of cavitation but not RPM. Until limiter kicks in unless you are letting off throttle of course. That's no longer WOT though. Cavitation/aeration at such @#& plate position likely indicates that you can use more aggressive prop since you have extra ponies under hood that are not spent needlessly cutting water.

I suppose if purpose of this post is to avoid transom splashing, avoid changing stock propeller to better performing one. Then you are right on the money. I'm just not convinced that it's exactly what many people expect from such guidelines.

Appreciate an effort you are making for community but I beleive there are some flows in the theory.
Happy Boating
 

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

I think we have a real world comparison of someone with experience correcting problems with one hull/motor combination attempting to go head to head with someone who matches boats and engines as a vocation. In other words, it is an amateur vs pro discussion, and the amateur is in over his head.
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

You see key difference here. Yes I'm amateur, but to solve my problem all I did was follow common industry practice. Open a book, even simple owners manual, review standard advice, and voila. And it worked. I didn't have to invent anything. Outboards, inflatables, speed tubes, ribs, high speed boats weren't invented yesterday. Everything you have to know pretty much is already known. Most of problems had been solved many times over already. Decades ago in fact. All you need to do is look for well known solution.
 

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

Yet you fail to see the solution described by the OP and understand it is using the principles you read in the books with much information added. It would be rare that anyone described the function of the anti splash plate positioned above the AC plate which is incorporated on outboard motors. In fact, his is the first thorough explanation I have seen in print. Due to the tubes extending behind the boat in an inflatable, water splash is sometimes a real problem with the designs.

I spent better than 30 years correcting mistakes made by so-called experts in pumping systems in industrial plants. The folks thought they were following the book but made very expensive mistakes in applying the theory. We can all learn, but we learn best with our ears open, not by challenging the ones providing good information.

You keep harping on the amount of the lower unit submerged without realizing that that is a given covered in his discussion.

It is good that you have managed to mount your engine in such a way as to give good performance. Had you run into a bad splashing situation such as he explains, you would find his discussion very useful. Hopefully he has helped others by taking the time to explain the factors which must be taken into consideration.
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

Did I say or argue anything about splashes? What is your specific point of contention outside of fondness of OP. I only argue for appropriate mounted height for sake of performance. I have concrete albeit limited experimental proof that it works in total agreement with common standards. OP didn't present much beside single (inconclusive IMHO) experiment either. Do you have any specific data point or experience? There seem be total disdain for "myths" postulated by any other sources. Still here is exert from Tohatsu manual. Do you suggest they are totally clueless about their own product?
pBKe-aVYqjSZ4wCJL92H8GId0I-pjUl9C3jmiIfZ6-A=w563-h822-no

If the height difference exceeds 0~~30 mm. engine power performance is likely to be reduced as as result of increased water resistance to the gear case assembly
Honestly if I had to deal with some splashes to offset 20% gains in performance/fuel economy I'd gladly do so. In reality of course my "spashes" situation only got better.
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

Here is another good read. Tons of useful information. Royce's Powerboating Illustrated - Patrick M. Royce - Google Books
You can get hardcopy on amazon for $0.01
The best designed gear housing has tremendous PARASITIC DRAG. The top speed can be increase if the motor can be raise 1/2" above normal without cavitating. Mounting motor lower than normal will increase parasitic drag This increases wasteful forces on the clamp bracket and transom reducing boat speed.
OP seem to think otherwise.
Deflector plate function mostly is not described for simple reason that with properly mounted motor it will just do it's job silently just like many other nifty features present on modern outboards.
 
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fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

You really need to reread the OP's posts.

If you are really out for max speed, how about a surface piercing cleaver.

I only have about 60 years of boating experience by the way. And he did discuss things you will not find in your web browsing.
 
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SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

Can you be more specific? I have problem with following:
LU+Performance.JPG

*
Wot+Test.JPG
 

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

Try reading what the man said.
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

I don't have problem being called an idiot and sticking my nose into correct answer but you have to be specific. "Read man's post" is not specific. What is your personal take on mounting height or distance between anti-cavitation plate to keel? Should we generally mount motors as shown above (Test1)? Does mounting motor lower increase resistance or make no difference?
 

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

He was giving an illustration of the area of the motor foot which must be addressed, not saying to lower the motor on the transom. You must comprehend what he is saying instead of trying to put words in his mouth.

A little knowledge is indeed dangerous. Note that the anti-splash plate is below the bottom of the hull in the illustration and would create all sorts of problems. He is definitely not recommending the motor be mounted in that position as you are trying to say. If you read the part where he took the factory rep from the motor manufacturer for a ride, you would possibly understand what he is saying.

Just how many motors have you matched to hulls anyway? He is very experienced as a dealer, but it appears you do not have that background but just enjoy arguing about things you may not have a good understanding of. That would be clear to anyone following your remarks.

On another site, it appears you have no understanding of the effect of a hooked hull and attempt to avoid understanding basics. That would indicate someone who is just out to create a stir. Someone so inexperienced would not be allowed to touch one of my hulls.
 

fbpooler

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Re: ABC Sib-Rib Installation Guidelines.-

I am going to disengage from this conversation, as the temptation to become abusive towards you is too great. If you really do not understand the OP, then that is your loss.
 

SIBRider

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Re: ABC Sib-Rib Installation Guidelines.-

Fair enough. I asked simple question. I'm open to be educated. You are avoiding answer. On the other forum same picture by OP baffled people just as much in a same manner. Point of instructions and guidelines is being direct not open to interpretation. If you take it for what it is how else would you interpret this?
LU+Performance.JPG

Picture is worth a thousand words they say.
 

Sea Rider

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Re: ABC Sib-Rib Installation Guidelines.-

Mama Mia, so the cracy discussion still goes on, Sibrider, which issue you don't plainly understand about upper posted pic. The problem with you is that you're a very theoretical man, cast on stone, owner's manuals, word of mouth blindly follower, these concepts not always works as stated, must be proved and tested under trial and error, that's how man perfectly flew.

The issue is that everybody reffers to the AV plate being the only LU part that does a job, what's staated on manuals 1-2.5" measured from AV plate to keel is just a refference, bear in mind that once boat is at plane boat tends to raise and given distance could not match due to hull shape. The worst stupid thing you can do is chop or raise an engine to match what's being stated on manuals to find out once on water that you've totally screwed it. Always recommend sitingt engine on transom and check it's water perrformance at wot, then decide the fastest or cheapest solution..

On larger much heavier engines 60+ HP which doesn't have engine clamps lowering or raising them is more complicated to work with as all of them are transom bolted and have control cables that need to be re arranged accordingly, usually are long shafft, it having water splashes at middle transom, not an issue due to having more power to compensate, ridding on higher transoms heights won't see splashes once sittting on deck. On an inflatable seeing water splashes is obvious. When reffering to water splashes, are the ones produces on middle transom by the engine's LU, not the splashes seen at end sides of tubes which every boat produces.-

Been following your post at the other side of the pond on Proyectil's thread, too much endless theoretical discussions that doesn't apply, you keep mixing spped tubes sibs with standard sibs, to each his own. How can you recommend changing stock prop for a different pitch size when the man hasn't solved his boating issues with current prop yet, out of this world..

BTW, this engine/transom height optimizartion can be done with any brand engine/boat combo, that is if you happen to be a maniac wanting boating perfection.. Let me some days to prove this with pics not plain theory.-

Happy Boating
 
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Sea Rider

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Hydrodinamics Exam.-

Hydrodinamics Exam.-

Sibrider,

Have elaborated expressely for you a hydrodinamics lower tail exam to check your general engine mounting understanding: Neptune, my sea lion pal wants to have his engine perfectly height transom seated on his standard 380 inflatable, he's requesting fond tech advise, can you hepl him out, check pick : Question, at wot, which leg height number will you match for water level & flow to pass by and why, give your full theoretical concept.-

Happy Boating
 

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