Prop For Best Speed

[work2pay4fishing]

I have 2009 Pro Craft 210 Super Pro with a 2006  225 Mercury Pro XS Optimax with 10 inch jack plate , I bought it a year ago and when i got it it had a Tempest Plus three blade prop 26 pitch that was a little rough, I bought a new prop and when I took it to the lake it would only run about 5200 RPM's and 56 mph, This last summer I bought a Trophy Plus 4 blade and 23 pitch, Also found that the motor was to low in the water.Raised motor and installed prop and now have boat running about 68 mph and RPM's about 5400. Boat comes out of hole pretty good , but feel like boat doesn't lift up on pad and can get more RPM's out of motor and more speed.  Looking to see if anyone out there has same boat and what their set up is and what it's running? 

 

Also have problem with trim, When trimming up or down the motor drops RPM's and slows down and as soon as you let off switch motor picks right back up. RPM's drop about 800 and also noticed voltage will drop down to battery voltage, I have a 1000 cca battery in it and alternator seems to be charging good. Any idea's for problem. This one is driving me NUTS!!!!!!!!!!!!!!!!!!!

 

Any thoughts greatly appreciated .

[A-Jay]

Hello and Welcome to Bass Resource ~

 

These prop pitch / speed calculators may help

 

A-Jay

 

http://rbbi.com/folders/prop/propcalc.htm

 

http://rcpro.org/rccalc/PitchSpeed.aspx

[Glenn]

Perhaps of interest...

 

http://www.bassresource.com/fishing/props.html

http://www.bassresource.com/fishing/outboard.html

[WIGuide]

If your motor actually drops rpm's when you trim you might want to get that looked at first before you go off buying props. You might want to double check that your motor is actually dropping the RPM and not just you tach doing goofy things. 

[slonezp]

You should be able to squeeze 2-300 more rpms before the motor is maxed out

[Al Wolbach]

 

If your motor actually drops rpm's when you trim you might want to get that looked at first before you go off buying props. You might want to double check that your motor is actually dropping the RPM and not just you tach doing goofy things.

I agree, sounds like you may have a problem with your tach. You need to correct that problem first, then attack the prop. If your rpm drop every time you use the trim slightly something is wrong and the tach is the first place I would look.

[work2pay4fishing]

These are different problems. Prop deal I am trying to get more transom left and speed and rpm's up. The trim deal is something else that is drawing to many amps and takes away from elec system. It's like trim pump motor drawing to much amps. I can watch the tach or the voltage and both are going down when trimming up or down and you can feel motor lag.

[gulfcaptain]

You do know a 4 blade will give you a quicker hole shot but the motor will loose a little on the top end due to load.  4 blades gives you more prop in the water at any given time which will cause drag and although you're engine is running 200-300rpms below max you may have maxed out.  You can underpitch and wind the motor up more and loose speed though, or overpitch and loose rpms.  You might be able to go with a 24, but I wouldn't go anymore.  See if you can test run the 24 and see if you get the performance you're wanting if they will let you.  But you may already be maxed out where you're at performance wise.  Making the jump from 56mph to 68mph is a pretty big change in performance though.  

[BKeith]

It's better to error on the side of too little pitch than too much pitch with two stroke motors.  Two strokes don't like to be loaded down, and will do much better running at motors max rated rpm or even a tick over.  If looking at a prop that will put you 300 rpm below max versus one that will put you 100 rpm above max, go with the 100 above.  There are very few two strokes motors that it would be a problem turning them more than their max rating.  A couple you don't won't turn over are the old cross flow OMC,s, they developed harmonics that can break the crankshaft, The early Fichts, the injectors in those a too small and even their recommend max can make them lean and melt a piston, a couple of the Japanese have two piece crankshafts and that can sometime cause a problem, but for the lions share, a 100 or so over is not going to bother a thing.   Too much pitch will actually slow you down kill a lot of hole shot, and one slightly too small will not slow you down and give you much better hole shot. 

 

One suggestion before getting to far into prop swapping, get the motor checked out, make sure it's performing at peak performance or you may end up spending a whole bunch of money on the wrong size prop.

 

Also, you said the motor was too low and you raised it.  Sounds to me like you raised it too much.  You should start tuning with the motor about 4" below the pad to make and then work up from there in 1/2" increments watch the tach, water pressure gauge and gps.  When you see and increase in rpm but not speed you are too high, go back down 1/4".  If you feel a loss of bow lift, which sometimes goes along with a loss of speed, again, too high, go back down 1/4".   If you are having to run a lot of outward trim and kicking a tall rooster tail, you are too high, and possible to little setback.   With the right amount of set back and the right engine height, you motor should be at a neutral trim so all power is be applied in a forward direction, and not having to waste power lifting the bow of the boat with extra outward trim.  If everything else looks and feels good make sure you are not dropping water pressure in turns below recommended minimum, if so, you need to go back down

[Tom18xs]

The need for speed.  Here are the critical factors.

1. Research other boats similar to yours

2. Finding the below pad mearsuement.  A good place to start is 3.5" below pad.

3. How to measure below pad height.  Make sure boat is on level surface like garage floor or driveway.  Put level,  center and back of the boat.  Use trailer jack to raise and lower till level.   Put level on cavitation plate and trim up or down till level.   Measure center of boats bottom pad to the floor.  Measure center of the prop shaft to the floor.  Subtract prop shaft from bottom pad for bottom pad measurement.  

4. To adjust height you need to have a manual or hydraulic jack plate.  

5. Generally from my experience boats are set to low that cause RPM's to low.  Try and raise motor that comes close to rev. limiter specs on your motor.  

6.  Finding the sweet spot requires some time.  

7.  If you pursue the need for speed I highly recommend a WPSI gauge.  Don't go lower then 12psi  for motor safety.  I usually keep around 14psi.

8.  Fastest stock prop I've come to know is a Mercury Fury prop.  It runs flatter vs Tempest Plus which has more lift.  Fury's general are 1.5mph faster.  

9.  Your setup sounds like your motor is to low.   

[fishnkamp]

I agree with the guys suggesting you have a mechanic check out your engine for performance first.  He can also cross check his readings to verify the tach.  You mentioned you have tried several props.  I know the Trophy has the ports but I did not notice how many holes you open or closed or just reduced the openings.  Those holes help you wind the motor up faster which helps with your low end take off.  One owner says he has your boat with a 225ProXS  set 31/2 below the hull and has a top speed of 73 mph 

[Way2slow]

One thing you also have to remember, that old saying, it takes two to tango.  There is always the possibility you have boat problems.  Wet flotation foam, (though that's not as common as it used to be with the open cell foam).  I have seen more than one boat with a bad hull where the bunk boards were not properly adjusted and cause a serious rockers/hooks in the hull. 

A lot of people don't understand props and think if they want to go faster, they just put on a bigger prop.  It don't work like that.  Doing that normally makes you run slower. 

I would do like suggested, make sure the engine is making full power, Check out Boat Setup and see what people with similar setups are running.   Of course we all know a fisherman and bass boat driver won't tell a lie, but just in case, don't believe everything you see some of them post.  I've seen a lot of them post speeds with props that would have to be making pitch as it spins because even with zero slip, they claim to be running faster than the prop and rpm is capable of.  On average, bass boats have about 13% slip, good setups can get down around 9% and a few a little less but those numbers are usually from the Allison's, Bullets etc and a few that have invested large amounts of time and money on their setup.