Yamaha 200 HPDI on Boston Whaler Outrage 21 - low RPM's

Ryan_J

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Apr 5, 2013
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Ryan
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Jupiter 31 - twin Yamaha F300's
I have a 2003 Yamaha 200 HPDI on my 2000 Boston Whaler 21' Outrage. I've got it out of the water and doing work on it during the "off season". Can't really call it that but I had to make a mental break to pull it out. I had the outboard serviced and it has a clean bill of health but after reading up on that outboard I now know that I'm not getting the RPM's out of it that I should. Currently I get 47-4800 RPM at WOT when lightly loaded and trimmed out perfectly. It lists that I should get 5500-5700 RPM at WOT. I'm currently running a 15 1/4" X 17 SS prop.

Any tips or recommendations would be greatly appreciated. I'm having a hard time finding a shop that will let me demo a used 15 pitch prop before purchase. Any prop guy or shop recommendations? I'm in the Long Beach / OC area. Thanks!

Ryan-J



-Ryan_J
 

MATTANZA

old man of the sea, in training.
Aug 23, 2004
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RICK
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Boston Whaler 25' Outrage "MATTANZA II", 34' Radovcich "AMY ANNE" {when it needs to be fixed}
in theory, your props "pitch" moves the the boat 17" per revolution. have your prop re-pitched down an 1" or 2". it's like gearing in an auto.....
 

sbsurfer

I've posted enough I should edit this section
Feb 19, 2010
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29ft Radon - 15ft Hobie Power Skiff
Brian at Valley Prop in Ventura is a very helpful guy, I'd call him to see what he recommends. Seems like you're off by about 800 rpms or about 4 pitch in prop...every pitch is about 200 rpms. You might want to drop down from the 17 to a 13 imo. I'm dealing with something very similar with a Hobie Power Skiff project I have. It was way overpropped. I need to get to 5500 rpm but only able to get to 4500. Brian recommended going from my current 17 pitch to a 14. He set up the prop when I repowered my Radon perfectly btw.
 
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ShadBurke

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Oct 28, 2005
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Shad Burke
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22' Boston Whaler Guardians
I have a 14.25 X 17" you can try to see if your WOT RPM improves. Thats want I run on my heavier 22' Guardian and I see 6,000 RPM WOT light and 5,800 RPM loaded.

If you are propped correctly, might be wise to check fuel pressure on the ECM (a dealer task unless you have the laptop and software). Also, often when the VST screen is clogged, bad injector(s) or clogged screens behind injector(s) or preliminary failure of fuel pump(s), the result will be a 500-800 RPM loss.

If motor sat for some time without have fuel drained from motor, varnished old fuel can gum up the system pretty good.

Hope that helps.
 
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StinkEye

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Oct 2, 2013
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How's your top speed and acceleration? Does the prop ever cavitate (meaning it's overpowered)?
Too much diameter will have a simmilar effect as too much pitch.
Reducing pitch will give more acceleration at the cost of top end. Reducing diameter (only if it is too large) will allow your motor to reach it's full potential.
The rub is that in the absense of someone with a enormous knowledge base, it will take trial and error to get it optimal. I recomend taking ShadBurke up on the offer to try the 14.25 x 17. Before you do that, record your speed at various RPM's and time your time to plane and to top speed. Collect the same data with the different prop, then you will have meaningfull data to begin to make a decission. It would be great if you could find a 15.25 x 15 (or so) to try as well.
 

abdiver7777

abdiver7777
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Since piston travel = fuel mileage is there a compelling reason to increase rpm? I guess I would look at the torque curve of the engine....
 

StinkEye

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Since piston travel = fuel mileage is there a compelling reason to increase rpm? I guess I would look at the torque curve of the engine....
There are so many reasons your statement is incorrect that I will just point out the most obvious as it realtes to this discussion: A motor that is over-proped will likely be bogging at full throttle and just waisting gas. Imagine full throttle but the motor is being held back - that is putting undue stress on the motor and inefficient. Proped correctly, the motor can reach top RPM under less load. Proped correctly, the motor should be more efficient at all RPM settings.
Given your logic, we should all just put the largest prop on that will physically fit and hold RPM's to a minimum.
 
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sbsurfer

I've posted enough I should edit this section
Feb 19, 2010
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29ft Radon - 15ft Hobie Power Skiff
As I mentioned above I was having a similar issue with a custom Hobie Power Skiff that has a Yamaha 50hp. I was at 4500 rpms and needed about another thousand rpm's. I went from a 13 1/4 x 17p to a 13 x 14p and I got exactly what I was looking for thanks for Brian at Valley Prop.
 

Ryan_J

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Apr 5, 2013
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Jupiter 31 - twin Yamaha F300's
Guys - Thanks for all your thought and ideas. It seems that it's going to be a game of trial and error while recording performance changes between props. ShadBurke ..... PM sent.
 

Ryan_J

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Apr 5, 2013
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Long Beach, CA
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Ryan
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Jupiter 31 - twin Yamaha F300's
How's your top speed and acceleration? Does the prop ever cavitate (meaning it's overpowered)?

Too much diameter will have a simmilar effect as too much pitch.
Reducing pitch will give more acceleration at the cost of top end. Reducing diameter (only if it is too large) will allow your motor to reach it's full potential.
The rub is that in the absense of someone with a enormous knowledge base, it will take trial and error to get it optimal. I recomend taking ShadBurke up on the offer to try the 14.25 x 17. Before you do that, record your speed at various RPM's and time your time to plane and to top speed. Collect the same data with the different prop, then you will have meaningfull data to begin to make a decission. It would be great if you could find a 15.25 x 15 (or so) to try as well.
My top speed is about 35mph when I'm light and trimmed out in smooth water. Acceleration is good when light but a bit sluggish when 3-4 guys and bait tank full. Prop only cavitates when I trim up too high, not under normal conditions/settings.
Seems like this is the path I'm going to take. Going to try and coordinate with ShadBurke and try his prop. Thanks for your insight!

-Ryan_J
 

sickcat

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Aug 5, 2003
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While I understand your point on hitting the RPM spec @ WOT with an engine (the OPs case included) some people do over prop intentionally. Guys run boats at or around hull speed and run a diesel considerably overpropped at a point low in the RPM range where the torque output of the engine matches the highpoint of the props efficiency. The engine is not overloaded at that specific RPM. Big downside is you don't get a lot more RPM than that point and what RPM you do is VERY overloaded. While it is still done that old school way cause it is the cheapest way to get the highest MPG nowadays hybrid systems and variable pitch props are the way to do it.

There are so many reasons your statement is incorrect that I will just point out the most obvious as it realtes to this discussion: A motor that is over-proped will likely be bogging at full throttle and just waisting gas. Imagine full throttle but the motor is being held back - that is putting undue stress on the motor and inefficient. Proped correctly, the motor can reach top RPM under less load. Proped correctly, the motor should be more efficient at all RPM settings.
Given your logic, we should all just put the largest prop on that will physically fit and hold RPM's to a minimum.
 

tranandya

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Aug 18, 2010
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You might wanna check your engine height too make sure the cavitation plate is level or above the lowest parts of the hull by 1inch.