Posts: 102
Location: Bowling Green, KY | I have a 1997 Lowe 170 Bass Striker with a 60 HP Johnson with power tilt and trim.
Recently, I replaced my old beat up 14x17 OMC prop with a new Turning Point
Hustler 13 1/4x17 prop. Both are aluminum. My RPMs went from 5650 to 5300.
The WOT range on this motor is 5000-6000 RPM. I raised the motor one bolt hole
as it was mounted as low as it would go and it gained me back about 100 revs. at
optimum trim, NOT maximum trim. I can gain RPM by continuing to trim up but the
boat starts to want to porpoise and speed goes down so they are not "useful" RPM.
I would like to get back above 5500 RPM so I was thinking about going up another
bolt hole. I have plenty of water pressure. Does anybody have any experince
with these semi-vee bass tracker style boat hulls? I don't know whether to fool with this or just drop two inches in pitch on the prop. Turning Point uses an
interchangable hub system so I could order a new prop housing for around $80.00
and save this one for a spare. Sorry about being long winded, thanks, Roger. |
Posts: 3514
Location: Elk River, Minnesota | Hiya,
Heck...just for seeing what it can do, move it up to the highest mounting position...you may surprise yourself and it will work well. When you test, get to WOT and put the boat into a moderate turn (nothing extreme but more than just a normal easy turn). If the prop breaks loose, drop the motor one hole and test again.
Water pressure will not ever be an issue since you are staying within the designed bolt holes on the motor. When water pressure becomes an issue, it is due to putting a jack-plate on the transom allowing really high motor heights.
Most dealers will mount the motor one bolt-hole up off the transom...it is usually a position that allows for decent economy and good overall handling, but definitely NOT the most efficient height for the motor.
If you went up and gained 100 RPMs, move it two more and you could potentially be right in the sweet spot. The only caution I would have with going 2 holes is you are still using aluminum...but one never knows until they try.
Good luck with it. Fun project if you like to "fiddle" with things
Oh...one thing with trim. It is as you say...optimum trim angle. Trim is a funny thing...it continually needs to be adjusted for what you are doing as it compares to the conditions you are in. In the best scenario, getting your bow up off the water and your motor leg perpendicular with the water's surface is the most ideal. Your prop wash should Never go above your motor cover...if it does, you are losing thrust. When you get to porpoising, your prop is losing its grip, and the bow falls...then it grabs again, and falls...trimming down is the right thing to do....get it right to that edge and that is where you want it while running...no more, no less..
Steve
Edited by VMS 8/21/2008 7:16 AM
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