Posts: 3472
Location: Elk River, Minnesota | Hiya,
Many of the navigator 175's have had 115 hp engines put on them and they do perfectly fine... Many were set up that way which made for a nice price-point in selling. It is not to say a bad boat comes out now and then, but I highly doubt that your boat is the issue.
With the 115 hp engine on the rig, it will not be anywhere near as fast coming out of the hole as the 115 has a smaller engine displacement as the 150 series of motors. Smaller displacement means less low-end torque, thus the slowness coming out of the hole. I am sorry to say, that the only way to increase hole-shot is to go down in pitch or up in HP.
Now...in terms of props, the aluminum is good for all around when the motor is mounted low on the transom (on the transom or one bolt up). If you switch to a steel prop of the same pitch, diameter and design, rpms go down about 200 and all you gain is durability. If you switch to something like the yamaha Pro-series prop, or to...say a michigan rapture or michigan ballistic, you might be pleasantly surprised at how it will wake the boat up.
If you are turning 5400 with your current steel prop you are definitely on the low end of things, which would suggest a pitch change to a 17...and for that rig, a 17 pitch rapture or ballistic would be very well fitted for the boat....but there is only one way to find that out. That is...to test them. I used to run a 90hp yamaha on the back of my 165 navigator and went with a 17 pitch ballistic and it was a great prop!! It did everything I needed it to do and I was able to move my motor up to the highest mounted position on the boat without too much loss of handling. That particular prop has very heavy trailing edge and tip cupping to lift the entire boat. And...that particular 90hp motor was the smallest displacement of all the 90hp motors out there... It was always sluggish out of the hole...that was never going to change unless I changed motors. (I upgraded to a 90hp johnson, going from 69cid in the yamaha to 105cid in the Johnson....a huge change)
The rapture, on the other hand, has bigger ears overall, but is vented, which is there to help your hole-shot by allowing some exhaust gasses pass through the hub and into the blades so they spin up to a higher rpm. Once a certain rpm is hit, the exhaust pressure is high enough the exhaust will not pass through the vent holes...and up the boat goes out of the hole.
I'd bet there is nothing wrong with the boat... A correct prop will take care of things. A good 17 pitch rapture or Ballistic but check on the yamaha pro-series also...itwould do you well... I believe Yamaha might be making a 17 pitch pro series at this point. if you are still a touch low on rpms the motor most likely can come up a hole or two.
19 in steel is most likely too much pitch, causing your issues...
Steve
Edited by VMS 5/18/2017 11:59 AM
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