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Discussion Starter · #1 ·
Hey guys! I know there are only a handfull of you out there with the same boat set up! I acquired this boat a few weeks ago! The motor has a 13 1/4 x 17 stainless 3 blade prop! If i run wot with tilt down, it digs the bow down really bad, if i run it at a smoothe position, wot, it runs 5200 rpm, at 35 mph, if i tilt it up a little more, i get 5600 rpm, at 38 mph, but porpises like a frikin 800 lb dolphin on a 4 ft wave!
It just seems like the Yamaha should get more speed!
At 5200 rpm , it seems like it has a lot more to put out!
Any input appreciated, especially those of you with the 70 on a Copperhead!!
Btw love the boat!
 

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Discussion Starter · #2 ·
Ok
So, i called the people at power tech, and he recomended the SCD 3 , its a 15 pitch. He said i need to be hittin 6300 rpm at wot or i could damage the engine! The prop on the boat looks Lmost new, so i will prob put it up for sale when i swap
 

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Living & Dying in 3/4 Time
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He said i need to be hittin 6300 rpm at wot or i could damage the engine!
Please define this better! Max RPM is 6300 on this motor and I want to say where it truly makes 70hp. I don't understand the "damage" statement.
 

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Discussion Starter · #4 ·
All i know is Michael at Power Tech said this engine is designed to run at 6300 rpm at wot . If its wot and running at low rpm, it can cause engine damage, and running at low speeds, at lower rpms , can even caus oil pump malfunction!
Im no boat motor person, so i dont even know if thats true!
U can call and ask if u want!
All i know is my boats turning 5200, and should be turnin 6300!
 

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Discussion Starter · #5 ·
If anyone out there knows for sure, jump in!
I dont want to buy a new prop if i dont need it!
From what i understand, it will help hole shot, and raise rpm, but i dont care about hole shot!
 

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Discussion Starter · #6 ·
Just got off the phone with Yamaha dealer
He said a few hundred rpms arent going to be a big deal, but the 15 pitch would increase holeshot and raise rpms!
Sorry to keep answering my posts!
 

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Living & Dying in 3/4 Time
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You definitely need to get the WOT rpm's up to near max. I'd trust the guys at Powertech, they are pretty darn good at what they do.
 

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He said i need to be hittin 6300 rpm at wot or i could damage the engine!
Please define this better! Max RPM is 6300 on this motor and I want to say where it truly makes 70hp.  I don't understand the "damage" statement.
Correctly propping an outboard is the most important factor in engine life. Here, "pitch" is the crucial element. Simply put, pitch—expressed in inches—is the distance a propeller would travel forward in one complete revolution under ideal conditions, i.e., no cavitation, slippage, or friction.

"Underpropping", which means installing a propeller with too little pitch, can lead to over-revving the outboard, causing subsequent failure of the reed valves (one-way "gates" between the carburetors and crankcase) and even the crankshaft. Both are very expensive to replace. Conversely, "overpropping", or installing a wheel with too much pitch, can result in coking of the rings, predetonation (usually undetectable), and, so, piston failure, necessitating a costly rebuild. With the high alcohol content and generally poor quality of today's gasoline, the likelihood of this latter problem occurring is very high.
 

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My copperhead with the 60 ran 39-41mph at 5600 rpms depending conditions and scenario. I couldn't make it porpoise if I tried. It did want to dig the nose of the motor was trimmed down, so I'll just trim way high.
 

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Discussion Starter · #10 ·
Ok
Thanks for the input!
I guess i'll go with the SCD 3
Ankona can save me a chunk on what i can oeder it directly from power tech!
 

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Since the boat starts to plow at wot it tells me the motor is to low.
I would raise the motor one hole and see if that helps.
 
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