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Location: Windy City | I am currently running a three blade stainless steel 21-m prop on my Yamaha 150 four stroke. The boat its on is a Fishhawk 1850. WOT is around 51-5200 trimmed as high as possible on glasslike water. I am under the impression the motor should be run as close to 6000 rpms as possible. Would I be considered overpropped? I am not all that familiar with props and pitches so any and all help is appreciated.
Thanks
Edited by one last cast 3/27/2010 12:15 PM
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Posts: 814
| You are overpropped. Try a 19p stainless should put you up around 5800 or so. |
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Posts: 3480
Location: Elk River, Minnesota | Good Morning!!
Couple of questions for you to start out. First, when you are running the 5100 - 5200 RPM's, what is your load like (People, gear, etc) Also, what hole position is your motor in (#1 hole is lowest motor position with the motor flat to the transom). With this little bit of information, there are a few things that can be recommended to try which might involve a prop change as was mentioned.
My gut instinct says you are overpropped as well, but I have a feeling that a 19 pitch might be a bit much yet. Each inch of pitch will add/reduce roughly 200 RPM's, so going with a 19 pitch theoretically would only get you to around 5600. With a motor height change, though, you might tweek out 5800 by going up a couple holes, which on that boat, should be a positive change. Most V-hulled rigs like yours can have the anti-ventilation plate about 2 inches above the lowest part of the hull and still have great handling and definitely more speed. There is a limit to everything, though, which means as you move the motor up, a slight decrease in handling and more ventilation can take place.
I should also ask...is the prop you have a black stainless prop? If so, I would highly suggest trying different props. The yamaha pro series propellers are outstanding props for both bite on the water and for higher motor heights (which I have a feeling will be something to get more RPM's as well) If you can find a good dealer that has demo props, I would see if you can get 3 or 4 different ones to try and head to the lake for testing. One will stand out well above the others which will give you optimum speed and lift, which will make the boat just float along at cruising speed, and really perform well at high speed.
Lots of variables in this, but if you enjoy tinkering, this is a fun project.
Steve |
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Location: Windy City | I believe it's a pro series Yamaha propeller. It is not the black finish its the chrome finish and I am running solo with 100 or so pounds of gear, livewell plugged etc. I'm not sure about the hole position but I think it is the second from the top. I will find out for sure and get back to you. Just to confirm, the closer to 6000 rpms the better with that motor? I don't mind tinkering at all and would like to find the right prop for the boat. Thanks for your help.
Edited by one last cast 3/28/2010 12:48 PM
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Posts: 3480
Location: Elk River, Minnesota | If the max RPM for the motor is 6000, it is best to be within the upper 1/3 of the RPM range under light load. Reason for this is when you fish with other people, more gear, etc, you don't have to make a prop change to accommodate.
If you are running a pro series prop, I would definitely recommend moving that motor up to the highest position on the transom, and dropping 2 inches in pitch. That should get you close, When it is all said and done, I would bet you will see an increase of 600 or so RPM's, a gain in speed, and a siginificant gain in hole-shot.
I should have asked that...how is your current hole-shot?
Steve
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Location: Windy City | The hole shot is really good. I am on plane within two seconds or so. Aside from the finish is there any other way to determine if its a pro series? It is a three blade that says 21-M on the the round part for what its worth.
Thanks
Edited by one last cast 3/28/2010 12:59 PM
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
The pro series prop will have vent "slots" cut along the hub. They will look like rectangles with a circular top on them. Not huge cuts but probably about 1/4" to 3/8" wide or so.
Steve
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