Help with 2021 521L

[jonboat521]

Picked up new 521L with 250 Merc..

Had it 2 months now and i am having some issues finding the "sweet" spot on the hydraulic plate..

I have run the plate from the bottom to the top and back .. and can seem to only squeeze out 59-60 MPH at it's best.. top RPM around 5500-5600...

I have taken back to dealer and they have verified all is good on motor.. 100% throttle.. hot foot etc.. Said they took it out and had it up to 68-69 Mph.. told me pretty much that i can't drive it.. I have NEVER had an issue driving a boat and getting it to perform..

i have run Ranger's all my life and just sold my 2012 520 that i could get to 72-73mph anytime i wanted..

Not sure if anyone else has had issues and or suggestions..

I am going to get with dealer and have them go run the boat with me to "show me" what i am doing wrong..

[MengRanger]

This would not be apples to apples - 2020 521L / Merc - I usually have mine at about 2.5 on Atlas. Max trim and then bump down slightly. I have yet to get fully aired out yet due to boat traffic. But 65 is easy to get to and I have seen 69. Expecting to be right at 70 solo when conditions allow.

[jonboat521]

thanks for Reply ... 2.5 on the Tape on the PLate ?? or the gauge on console ?

[GhostComanche]

That boat will perform at its best with a all around height of 3.25" pad to center...........................measure from the floor to the pad and then from center shaft to the floor. The difference between measurements with be your pad to center. When dead on at 3.25", put a mark on the plate so that you will know where it is at......................RR

[MengRanger]

2.5 is on the Atlas - so can't be sure what the actual P to P is. Will find out this fall when the heat goes WAY down. I am not laying on blacktop for the quite a while. I definitely run it lower than with my older 2 stroke.

[EDR]

I’ve got same boat in a 2019 with the Merc 4S. If you have the Atlas jack plate with the Atlas gauge try 9 to 11 on the digital readout. Should be able to get anywhere from 65 to 69 out of it depending on load and conditions. This time of year in Oklahoma loaded with 2 people 66 is about it in mine.

[Mcqtr]

I’ve got same boat in a 2019 with the Merc 4S. If you have the Atlas jack plate with the Atlas gauge try 9 to 11 on the digital readout. Should be able to get anywhere from 65 to 69 out of it depending on load and conditions. This time of year in Oklahoma loaded with 2 people 66 is about it in mine.

Those are realistic numbers. Mine runs the fastest on 8 but it is a SHO. 68.3 is the fastest I have seen it and 2 people tourney load is 65ish.

[flyingwillie]

Mine is a 2020 with a SHO. Regardless of prop you should be getting 68-69 mph. You have to find the sweet spot using both trim and JP. I run 2” on the JP tape and 50% trim. You can feel the motor “exhale” and that’s the sweet spot.

[dean c]

I’d ask what prop you’re running before giving advice.

[mikesxpress]

The 4.6L CMS 250hp V8 needs to run at 6200 rpms WOT to maximize the fuel the fuel economy and performance across all power bands. List the propeller your running. Is it a box prop or has it been true pitched. Allot more information on this on the Mercury 4 stroke board.

*A 23P Fury 3 blade is the dominant prop for the 250 V8 on 20'+ boats. Any P to P information is irrelevant unless it's the exact hull/jackplate/V8 engine. The V8's Torquemaster gearcase is significantly different than the Opti.

[TripleT]

I seem to not see a difference when I raise mine above 2 or 3 and 3/4 trim.

[jonboat521]

Thanks guys...

For those that ask.. it is Merc 4 stroke... 23 Fury...

Measured the Prop to Pad and got ballpark on where it needs to be on the gauge..

Got to run it for a Very Brief amount of time yesterday ... saw 61-62 without messing much with it.. so some progress made....

This boat/setup seems much more picky and will not tolerate changes on height of plate at all...

[1BADAIR]

is it lifting the bow? heavy tackle in the bow? I'm not a fan of the fury on a 21 ranger or a bow heavy boat. Tempest works better for that

[Bryan O]

I basically had the same expirence you did coming out of a 520/250 ProXS 2 stroke going to a 521/250 ProXS V8. What I had to learn from trial and error was that this boat seems to like the motor much lower than my 520 did. I was running mine with the plate (Atlas) too high, and it wasn’t lifting the boat. I typically ran the 520 (smooth water) at 6-9 on the dial. The 521 would fall flat and not lift that high with the plate. It likes the plate down at about 2 - 5 on the dial. Then it carries the bow higher, and will run close to 70. I’m also running a 23 Fury and it turns it 6250RPM. I’m going to try a 25 Fury with extra vent holes that I had worked by Croxton this weekend. I think it’s too much pitch, but we’ll see what it does.

[printman71]

Pitch, and "health" of prop is first concern. What the jackplate "reads" is irrelevant due to which holes everything is mounted in. As stated above, park it level and set the engine prop shaft at 3.25" below the pad and see what the reading on the jack plate is. That would be the starting place of moving up or down for desired performance.

[jc2bg]

Bryan [above] makes a point that is too easily overlooked by some. It’s not necessarily true that greater engine height and/or more trim angle equals greater speed. The bow has to lift in order to get the boat truly up on pad, and until it does, speeds are going to be well below expectations. Some setups require the prop to be deeper in the water in order to get the right leverage.

[B. Dillon]

I call BS that your dealer took it out and touched 69 in the summer. Video or that didn't happen!

[jonboat521]

Got to run it yesterday .. was able to get 61mph.. 5650 RPM... best i could do .. and engine was as low as it would go on the plate..

I did level the boat .. and measure and note the height of the plate at 3.25" boat is a slug with no lift when i run it at that height..

Starting to wonder if prop is not right.. or something else is wrong..

[B. Dillon]

Got to run it yesterday .. was able to get 61mph.. 5650 RPM... best i could do .. and engine was as low as it would go on the plate..

I did level the boat .. and measure and note the height of the plate at 3.25" boat is a slug with no lift when i run it at that height..

Starting to wonder if prop is not right.. or something else is wrong..

I know how frustrated you probably are. I had the same issue and it was the hot foot demand linear calibration something or other that had to be fixed with merc software AND had to order a new (longer I think) throttle cable. My best performance is with my atlas hydraulic jack plate at 7 on the digital gauge.

2019 521L 23p fury

I still don't believe your dealer touched 69 when you can't. The boat drives itself and doesn't take a bad ass pilot to at least touch 67.

[Mike Stephens]

521L now is very hard to lift. Mine is OK with bravo 1 xs 25. Now get a lot of bow lift. None of the Fury 3 or 4 are any good on this hull. Mercury racing is now reccomends Bravo 1 LT 24 for the Z521l.