Causes for Disappointing Top End on '07 250 ProXS???

Don: I'm about done dialing in the performance on my rig (if you recall, 2007 Triton 215X w/ 250 ProXS). I have tried about 8 props and every engine height. Based on comparing notes with others with the same setup as me (on Walleye Central boards), others seem to consistently get 3 to 5 mph more on top end, and some of them have hardly done anything to dial in their rigs.

Anything that would cause top end to be approx 3 to 5 mph below where it should be on the '07 250 ProXS but would otherwise not significantly adversely affect overall performance? The motor seems fairly smooth and has decent holeshot and decent mid range and I have been propped between 5800 and 5900rpms. I get an average of 4.5 mpg per SmartCraft if that matters. The throttle plates do appear to be opening completely.

And to answer your question (before you ask it), I have been using Seafoam with every tank of gas. I have noticed fairly quick accumulations of soot on the INSIDE of new props I have tried (not on the outside). As a result, I have just switched to Quickleen.

I think I have about 60 hours on the motor (I wil have to check to be sure on this).

I do not have any good reliable Merc certified mechanics in my area, so if anything comes to mind to point me in the right direction I would appreciate it. Thanks! http://www.bassboatcentral.com/smileys/popcorn.gif

What elevation are you running. Every 300 to 400 ft above sea level you will lose about 1 mph.

Good point. Unfortunately, I am only 800' above msl. Well, I guess I should say "fortunately" because being only at an elevation of 800' above msl should not be the cause of disappointing results with top end performance when others getting better results are at higher elevations.

I actually just received some additional feedback from another person that has the same rig as mine (Triton 215X) but he has a 2004 Merc 250 EFI...and he has better top end than I do. We're getting into apples and oranges with this particular comparison a bit, but just out of curiosity, shouldn't a 2007 250 ProXS be stronger than a 2004 250 EFI?



Modified by rpr at 12:27 PM 5/31/2009

Do you mean a 2004 250 EFI or 250XS? The 2003 & 2004 250XS had the 5850 warning and 5950 limiter. There seems to be an opinion that the 2003 to 2005 XS motors were stronger (they require premium fuel) but I have not seen any dyno pulls on the later XS motors. Can't answer that question with any facts.

If the other motor is an EFI, they are very easy to mod and tune for more power (hood scop mod, mixture tuning, timing, etc.)

The XS motors lose power very rapidly after around 5700 RPMs, and on fast boats run the best speeds propped to turn 5500 to 5700 RPMS.

You haven't listed your current setup. (GPS speed, prop type & pitch, lower unit type and gear,RPMs with each prop, propshaft height).

For instance, if you are running a sportsmaster lower on your rig you will lose 3-5 mph.

List your current setup.

John: I strongly disagree that a 250 XS looses power after 5700 RPM! At 6000+ yes but not 5700 in my experience since 2006 on several 250 XS's. In fact I have NOT had one of them run under 5700 as well as they did above 5800 to 5900+ RPM's

Now a Walleye boat isn't Stroker but it's probably not that he has to run under 5700 RPM's

BTW: The picture of his boat looks like he's got a black lower unit so I doubt it's a Sportsmaster http://www.bassboatcentral.com/smileys/wink.gif

Rick:

Before we get into this a whole lot deeper....

Let's get some info:

1. Engine Serial Number
2. ALL numbers printed on the tags of your PCM/ECM. http://www.bassboatcentral.com/smileys/wink.gif

Ely, the dyno backs up my statement. Just because you have no trouble turning 6000 on a fast boat doesn't mean you are making max HP there. You aren't.

The Dyno and torque curves that I've seen from Eric and Wayne Worthy say that the torque and HP tops out right about 5900 to 6000. Go to Wayne's site and see the dyno chart of a stock 250 XS.

I also think that Don has recommended a bunch of times to prop the boat some where under 6000 but never said it's was above peak HP/Torque window at anything over 5700

I have run so many props at 5700 or a little less and NOT one has gone faster than amny of my props which turned 5800 to 6000, NOT more but not less

Most stock 3L's reach their "peak horsepower and torque" in the 5800-5950 RPM range. It varies slightly from one ending to the next...

The catch here, is that you can't necessarily use the "dyno test" of one motor to assume the exact "sweet spot" of another. http://www.bassboatcentral.com/smileys/wink.gif

Mercury's "propping" RPM recommendation for your engine is 5500-6000. If you can hit the 5800-5950 range (with a low prop slip ratio), you'll be in good shape. http://www.bassboatcentral.com/smileys/wink.gif

Rick- I'd still like to speak with you about the numbers on the PCM. http://www.bassboatcentral.com/smileys/wink.gif

Don: Aren't you confirming exactly what I just said http://www.bassboatcentral.com/smileys/smile.gif

"Not under 5700 but not over 6000" ( In my experience 5800 to just short of 6000 )

Dejavu..... seems like we've been right here before.

Yup Eli... saying pretty much the same thing.... you say below 6000, I say up to 5950.... and here were are with a "50 RPM Split again". http://www.bassboatcentral.com/smileys/roll.gif

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EuropeanAM &raquo;</TD></TR><TR><TD CLASS="quote">Rick- I'd still like to speak with you about the numbers on the PCM. http://www.bassboatcentral.com/smileys/wink.gif </TD></TR></TABLE>

Sorry, Don, haven't been out on the boat lately. Here is the info:

<U>Motor: 2007 250 ProXS</U>

SN: 1B471639
Feb 2007 Mfg Date
250XS XL


<U>PCM Labels (2)</U>

897906 012
Racing 250 HP
3.0L OPTI
704508 77

XR001GZZ
PCM0701
01-15-2007
897906


OK Don, work your magic. I expect no less than a revelation that there is some mystery buried in the above numbers that will allow you to find another 5mph hiding in my motor somewhere. http://www.bassboatcentral.com/smileys/praying.gif http://www.bassboatcentral.com/boardstuff2/beers.gif http://www.bassboatcentral.com/smileys/bows.gif

P.S.: For reference, or just interesting reading, refer to the attached BWB "shootout" using a very similar boat to mine (2190 lb hull weight compared to my 2300 lb hull weight) with 4 different engines, including a 250XS (but not a 250 ProXS).

http://www.mercuryracing.com/_...t.pdf

Rick- give me a call regarding the above info. http://www.bassboatcentral.com/smileys/wink.gif