2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

[rwerner43]

I just bought a 22ft Angler w/ 150 Yamaha Saltwater Series II Fuel Injected OX66

Boat was a lightly used rental at a high dollar resort.

Starts and runs great. I have not checked compression yet, but have no reason to believe it will be a problem.

I have a 15 x 17 Yamaha Prop on her and she will do 32mph at 4600 rpm WOT.

The throtle is pegged to the helm, but looking at the engine, off, WOT she has maybe 1/8" more she can go. Very slight.

At the advice of my prop guy I went to a 4 blade 13x14, and she did 22mph at 6000 rpm, rediculous.

SO I went down to a 14x17 and got the exact same! 32mph at 4600rpm.

I changed the tach to see if I was in fact hitting 5500ish, but the tach is fine.

Any ideas?

 

[99yam40]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

I would test compression on any motor I had that did not perform as I thought it should before doing anything else just to make sure.
Then I would have the motor run with the Yamaha test prop to see if it will put out the HP the motor is suppose to at that elevation.
If no problems are found with the motor Then I would be looking at the boat and motor set up to make sure it is done right and look at this site to see how a set up like it should perform. http://www.yamaha-motor.com/outboard/products/perfbull.aspx

 

[rwerner43]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

Compression is 113-117 in each.

 

[jeffersondodson561]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

What type of material? Stainless or Aluminum fresh or saltwater? A 4 blade will give you more hole shot while a 3 blade is better at accleration at planing speed. All this should be taken into consideration after you have verified engine condition. Their is a lot more to props than just diameter and pitch...

 

[jeffersondodson561]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

Look at this link if you have problems looking at this...

http://www.yamaha-motor.com/outboar...rop_pdfs/PIG_PropPages_12_13FINAl_FOR_WEB.pdf

 

[rwerner43]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

It is the factory Yamaha 17m prop that came on it. The 14" I tried is also stainless. I understand that all props are different, but there has to be a difference between a 14x17 and 15x17 stainless, and mine shows no difference in performance....

 

[99yam40]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

If your motor will not hit the proper RPMs with a prop the size of the one they used in the performance link I sent you the you have motor problems or set up problems. Like I said before have the motor run with the test prop at a dealer to see if it is the motor.

 

[SparkieBoat]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

different props can produce varying results..changing the diameter is not going to make much difference as you have found out..finding the exact right prop can be some trial and error..you need about 600 more RPMs..I would recommend testing a 15x15 or a 14x15. you will generally see less than 100 rpm difference with 1 inch change in diameter, sometimes no change (as you have experienced). sometime just changing prop manufacturer can change several hundred RPMs. forget the four blade..stick with 3 blades

 

[jeffersondodson561]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

Did they take into consideration the diameter of the gearcase? Or gear ratio?

 

[jeffersondodson561]

Re: 2002 OX66 150 won't rev above 4600rpm with 15" OR 14" prop

but there has to be a difference between a 14x17 and 15x17 stainless, and mine shows no difference in performance....

Pitch=The theoretical distance the propeller will travel in 1 revolution in a semi solid liquid (gellatin) with no slip.