Home › Forums › Bass Cat Boats › Prop change / up or down on jackplate?
Toadrustler.
I hope the answer to this question is up.I have a 2015 Margay that I just cant get the top speed running right. I have on it a 150hp Mercury XR6. It currently has a 23p tempest plus. With 2 men, too much tackle, and a full tank of gas I can just make 59mph at 5800rpm. When Im by myself I can break 60 but the chine walk is huge. It just seems like I cant get my boat on pad. I will get out of the hole and on plane great but just not on pad. I just measured 4.75″ from pad to centerline of my prop. If I raise it up I loose a lot of speed. I got a good deal on a used 25p tempest plus to try. Will I be able to raise my jackplate with more pitch? Any ideas for me?Thanks,Tom
How much are you raising it and how much speed are you loosing? Is it because youre hitting the limiter sooner? As raising it a 1/4″ should increase Rpms ~100rpm. Stepping up 2 pitches is going to drop Rpms quite a bit (~400), though raising engine height could gain some back as long as youre still getting good bite that allows lift. The higher the engine the less chine youll get, but also keep in mind the taller the pitch the slower the holeshot.Hope that helps, Chris
If i raise my engine roughly an inch my rpm wont go above say 5000. I just cant get enough of my boat out of the water. My top speed may be about 54mph when the plate is at 3.75. Also it seems like i can never get the bow of my boat up. If i trim up the engine just makes a big rooster tail. ThanksTom
First, I am almost certain a 25p is going to be too much for that motor. I owned one of the first XR-6 motors back in 1992. They generally liked a 24p Laser at the time, and some ran a 23p. Todays props are better than the laser, and a bit harder to turn. You are at the correct RPM range for that motor.First thing I would do is visit the mercury marine racing web site and use their prop slip calculator. For pitch, enter pitch + 1 for the tempest since it is a cupped prop. Find out what your slip is so that you can make informed changes. You will need to know your lower unit gear ratio. The small gear case XR-6 motors had the 1.78 smaller gear case which was not so durable. Some came with the bigger gear case which was probably the 1.87 ratio but I am not certain. Plug all of that in. If your slip is 10% or less, you are doing about what the motor is capable of.3.5″ prop to pad is a good starting point. Most will run a bit higher than that, but it all depends on weight, prop, balance of boat, etc. One obvious question, when you say “too much tackle” how much is too much and where is it located. If it is up front, that can be a killer. Something sounds wrong however, as your “if I raise my engine an inch it wont go above 5,000″ sounds like an impossibility. For each 1/4” you raise the motor, RPM has to climb since you have less lower unit and prop in the water. As RPM climbs, water pressure will drop and prop slip will go up. If thats not happening with your boat/motor/prop combination, theres something else wrong here.That motor needs to turn in the upper 5000 rpm range at WOT.2008 Pantera Classic2014 Mercury Pro XS 200
The margay is a little different beast for prop setup. This boat does not setup the same as other basscats, especially if theres extra weight involved. I had the same issue with being too high up with the prop. You dont get good nose lift and the boat never fully lifts correctly and you end up plowing too much. I would have to measure mine, but I know Im close to what you are using for height with my 150 4 stroke. Im using a 23 tempest also. I have to try it one of these days but I may try another 1/2″ lower and see if I get more lift/ better speed. my margay will only run about 56-57mph @ 5100 rpm with 2 guys and light tackle. Havent tried solo, but Im sure I could hit 60 or better that way. Have really been thinking of going down to a 21 or 22p tempest and trying them out as I usualy fish with 2 people and sometimes 3.Jared
Ive used the prop selector and pitch calculator and added the screenshot. So I have 14% slip it says. The 23p prop did just come back from Mark Croxton. Im still over by 200 rpms So I think he would repitch/cup it if I ask. Ive run 3.5 prop to pad and it just wont do it.I got a great price on the prop so if it is too much ( I agree it might be too much) it will be no big deal.
Who said to raise it an inch right off the bat? My guess is its then surfacing the prop so much that youre loosing lift which isnt putting you on final pad, sounds plausible as to why then it drops so much speed and rpm. The tempest has good lift, is all your weight up front and are you running a minn Kota trolling motor as neither help with bow lift. You have to find the happy median…too low cause you to over trim, shoot rooster, loose water psi and chine walk/too high causes you to loose lift and loose water psi
Until you figure out the chine walk deal youre always going to be scratching your head.
Ok, the puzzle just got worse I guess. I took the boat out today with the 25p tempest plus.original setup:4.75″ prop to pad23p tempest plus prop ( Mark croxton went over it)3 large hole pvs plugs5800rpm60mph bad chine walkNew setup:4.25″ prop to pad25p tempest plus (ebay)1 large hole pvs plug 2 with no holes5800rpm62mphHow the heck do I go up 2 on my pitch and not loose rpm?The chine walk was BAD. I could not hold it (dont claim to know how). Getting on plane with the 25p prop was not an issue. It only took slightly longer to get on plane than the 23p. It did seem easier to get on pad with the 25p prop.It seems silly but what the heck do I do now? 27p prop and 3.5 on my jackplate? I didnt think a 150 could spin a 27p prop.Im completely puzzled.
You can keep buying props and adjusting that jackplate and still get nowhere until you learn to balance that boat. I would start by putting the heavy tackle in the rear and the light tackle in the front. Take your time and slowly trim and keep it balanced. I hear about driving through the chine. But that isnt correct in my opinion. Balance the boat and make small corrections. Once you learn how to do this you will then be able to start adjusting the setup.
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