Wrong Prop?

OSUCowboy27

Recruit
Joined
May 12, 2008
Messages
5
Hi all, this is my first post and I am new to boating and do not know anything about props. I have a Blue Wave 189T, Yamaha C115 (w/Stingray), PowerTech M90PFB4P16 prop.

During rough conditions, I can't get the boat on plane. But when it is relatively calm, it will be about 3000 to 3500 rpm at WOT and then rev up as the boat slows almost like the prop cavitates. Also, in reverse, the boat will not go even as I increase rpm.

The prop is a stainless 4 blade 13"x16". I think I need a 3 blade 13.5x19 according to yamaha's website but any help would be appreciated.
 

walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: Wrong Prop?

In rough conditions, if the 4-bld won't plane it, I'm sure a 3 won't come close.
Is the engine mounted pretty high?
Where is the AV plate in relation to boat bottom when engine is level on trailer?

Another thought....Is there anything mounted on the transom, such as a transducer, speed-wheel, etc, with-in 12-14 inches of the center-line?
The reverse issue "may" be just a super high-rake prop.
Parabolic rake causes tremendous bite in fwd rotation, but the spoon effect causes a great loss of reverse control.
 

OSUCowboy27

Recruit
Joined
May 12, 2008
Messages
5
Re: Wrong Prop?

I will check the height of the motor. I do know that I do not have raise the motor after trailering the boat and part of that is due to the design of the boat. There is a "tunnel" that allows water to flow to the prop resulting in shallow water operation. I am going to contact Blue Wave and ask them for help as well.
 

ddaigle

Petty Officer 1st Class
Joined
Feb 9, 2004
Messages
332
Re: Wrong Prop?

Tunnel boats are a difficult breed to operate correctly. Sounds like your motor is too high. Do you have a jackplate? Are you trimming all the way down when taking off? The 4 blade powertechs are good props and a 16 pitch supercup is almost like a 19 pitch 3 blade. Either your motor is too high or all the cup is worn off the prop. High mounted tunnel boat motors need lots of cup or you will get no bite. I know from experience.
 

OSUCowboy27

Recruit
Joined
May 12, 2008
Messages
5
Re: Wrong Prop?

Tunnel boats are a difficult breed to operate correctly. Sounds like your motor is too high. Do you have a jackplate? Are you trimming all the way down when taking off? The 4 blade powertechs are good props and a 16 pitch supercup is almost like a 19 pitch 3 blade. Either your motor is too high or all the cup is worn off the prop. High mounted tunnel boat motors need lots of cup or you will get no bite. I know from experience.

Thanks for the reply. This is the info that I was needing. I also think the motor is too high. I do not have a jack plate and the motor is down as far as it goes. I do have the trim all the way down but the boat trolls great and has good hole shot. Does the PowerTech prop # listed above indicate supercup? Will a jack plate allow me to lower the motor or would I need to get a longer shaft if there is such a thing. Thanks
 

ddaigle

Petty Officer 1st Class
Joined
Feb 9, 2004
Messages
332
Re: Wrong Prop?

Im having trouble understanding your question, you said it wont plane and then you say it has a great holeshot? If the motor is all the way down it should be fine. Something is not right with your prop, either the hub is slipping or as I said all the cup is worn off. I dont think that is the supercup prop, but it is still a cupped prop and with no cup a tunnel boat has a hard time.
 
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