Prop Question.

[RonWilliams]

Prop Question.

I have a 16.6 Hydrasport with a 90hp johnson. All 95. I have a Raker 13.5x18 prop. I added a 30gal livewell to the center of the boat & now its lowsey on takeoff but flies at wot. I will check the RPMs this weekend but if I reduce the prop to 13.5x17 will this make much diference or will I need to go smaller? Thanks, Ron

 

[ob]

Re: Prop Question.

Re: Prop Question.

Before you consider propping down to improve your out of hole performance,insure that your motor is mounted at its optimal height on transom.Are there any additional holes in transom bracket that will allow you to do so?You would like to get it as high as possible without prop ventilating excessively while executing a tight turn on plane at around 2/3 throttle.Also,it would be helpful to know what rpms you are currently turning at WOT with the added weight.If you find that the current prop setup will allow your rig to turn in the upper range of the manufacturers recommended WOT rpm(5500) ,drilling vent holes ahead of the props blades leading edges may be an option to increase performance on hole shot.

 

[walleyehed]

Re: Prop Question.

Re: Prop Question.

The 13.5X18 RAKER should have factory vent-holes.<br />Thats the same prop I'm using on my 115 (97'), and I get around 5300 r's with engine up to 3rd hole. I can trim up fully (without ventilating to the point of loosing speed), and that RAKER corners very well. I would consider a repitch before I bought another prop. (IF your eng. mounting is set up correctly).<br />BTW, I gained about 125RPM per hole I moved up (lifted) the eng. from the transom.

 

[RonWilliams]

Re: Prop Question.

Re: Prop Question.

Im in the 3rd hole now. Their are holes in the side of the bracket. Could use one further in toward the transom allowing the motor to tilt inward raising the bow more on takeoff. I will know the RPMs this weekend. walleyehed, thanks for the repitch idea. if I need to change the pitch, thats what I will do. Will I notice much of a change by going to a 17" from the 18"? Thanks, Ron

 

[ob]

Re: Prop Question.

Re: Prop Question.

Ron ,The holes that I refered to are not the ones that position the motor on the tilt bracket rod when lowered,but the mounting holes that hold the motor to the boat transom.In many instances you can increase the engines rpm by as much as 100 by raising engine one hole.This will not effect the trim angle but rather allow your engine to operate under less drag and lower exhaust back pressure.Once this optimal setting is achieved, then make your final prop pitch decision based on rpms.Only a water test can confirm final placement.Without the engine being mounted to its optimal height ,you simply cannot attain its best high end performance.I am assuming that your engine is equipped with power trim and tilt.<br /><br />I raised my 70 hp two holes last summer and picked up 250 WOT rpms when trimmed out.Good luck.

 

[RonWilliams]

Re: Prop Question.

Re: Prop Question.

Sorry for the confusion. It is in the 3rd hole in the transom. I cant go any higher. I was wondering if the motor set in closer to the transom / would help push the bow down or cause problems with the carbs tilting to far back. Thanks, Ron

 

[walleyehed]

Re: Prop Question.

Re: Prop Question.

If you were wondering, ob and myself were saying the same thing. I didn't give a thought to the tilt pin, as most will be in the lowest, most inward hole possible with T-N-T.<br /> Re-pitch on the RAKER will get you about another 150 RPM...to change anymore would affect the rake and cause other things to change. <br />BTW, ob's findings on eng heighth meet mine exactly....about 125 RPM per hole UP.

 

[Dhadley]

Re: Prop Question.

Re: Prop Question.

Be careful when repitching a Raker. If the prop shop has the raker pitch blocks, youre OK. If not they will use the SST blocks and you will lose all the lift the Raker has.<br /><br />Ron, I dont really understand you last question. If the motor is in the 3rd mounting hole you should have one more to go up. And when you ask about moving the motor closer to the transom, are you saying you have a jackplate or a setback now? Or is the motor indeed mounted to the transom?<br /><br />Good luck!

 

[RonWilliams]

Re: Prop Question.

Re: Prop Question.

Dhadley, Thanks. Your right! Their is one more hole. My boat has the steped hull at the transom so I should have no problem raising it up one more. The last was Q was using T&T/pin. walleyehed answered my question. I will move it in to last hole. Thanks, Ron

 

[RonWilliams]

Re: Prop Question.

Re: Prop Question.

The WOT is good for 4700 & that is with just me & full livewell. I did not move the motor up yet. The water pickup would be right on the line. May pick up air. If I repitch, can I get an 18" to 16" safely? Thanks, Ron

 

[walleyehed]

Re: Prop Question.

Re: Prop Question.

As mentioned above, they must have the RAKER blocks for that prop and about 100-125RPM is all that can be gained. You'll never get the raker to 16" equivalent without destroying the prop.<br /> The raker pulls very hard, and works best partialy out of the water If you are only getting 4800, you need to go to a 13.5X15 SS to get the r's where you should be, providing you are going to leave the engine at the present hight.