Don, Red, or Eric maybe you could chime in here? What is the maximum WOT running temp before guardian kicks in on an 250 XS?
We always talk about water pressure #'s but I assume it's ultimately engine temp that kicks off guardian mode not the actual pressure?
I would be interested in the same question about a 300xs. When I do start raising the motor I will turn one of the smartcraft monitors to water temp, then watch pressure and temp. When it starts to go up I will lower the motor a bit.
Water Pressure AND Engine Temerature are both monitored by the PCM.
EITHER can log a fault, enabling Engine Guardian. The "Guardian Percentage" will reflect how the PCM "perceives" the situation. For instance, if low water pressure occurs, but engine temp is within acceptable limits, it may only limit to 70-95% "Available Power". However... you could have the reverse of the situation... and be limited to as low as "idle speed".
With 130 degree thermostats, overheat faults will set somewhere in the 160-167 degree range... enabling Engine Guardian.
Water pressure is a little tricky to pinpoint a "specific pressure"... as it would depend on numerous factors, including engine temperature, RPM, and the "length of time" pressure had been low.
Keep in mind... in the eyes of the PCM- a fault is not logged (in most cases) until "the preprogrammed limits of a particular sensor are out of range for at least 6 seconds".
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
At 6500+ rpm, it is about 2 seconds under 10# and your back down to 1200 rpm.
If your around 6200+/- then it will run into the overheat guardian before water pressure..
This is the best I can tell when running XXX and hitting guardian
If you hit water pressure guardian then you can turn key on and back off again to reset puter and keep running..
Overheat guardian gets a little more interesting
Don: Thanks for the feedback on an 250 XS at WOT 5800 to 6000 RPM can you give me an idea of what the minimum water pressure would be for a fault trigger and how long that pressure needs to be at that insufficient level VS the engine temp on the smartcraft?
Water pressure tends to build again with time as you run while it may be insufficient for a few seconds till it builds again while under very high speed ( over 95 MPH ) and high ( in excess of 5750 RPM's on an XS.
Lou: Never seen 6500 RPM's on an XS yet but probably will with the HT 250 XS Powerhead once it's on my boat
Eli, my #ers are base #ers that I observed, just back the rpm's down to your engine rpm ranges and I bet ya see the same..
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by esdbass »</TD></TR><TR><TD CLASS="quote">Don: Thanks for the feedback on an 250 XS at WOT 5800 to 6000 RPM can you give me an idea of what the minimum water pressure would be for a fault trigger and how long that pressure needs to be at that insufficient level VS the engine temp on the smartcraft?
Water pressure tends to build again with time as you run while it may be insufficient for a few seconds till it builds again while under very high speed ( over 95 MPH ) and high ( in excess of 5750 RPM's on an XS. </TD></TR></TABLE>
The programming for each engine's calibration varies. And, the situation has to be looked at on a "case by case" basis, as engine speed, boat setup, and actual running temperature varies not only on different engine setups, but from run to run on the SAME setup.
LOW water pressure will usually trigger a fault if the water pressure is "substantially" below the programmed threshold (or expected range) for a period of 30 seconds or more (perhaps less time at a higher RPM). The Water Pressure Sensor (or Block Pressure Sensor) is very accurate, and can report even the smallest changes in water pressure. A fault is usually triggered when the PCM perceives there to be "essentially NO water pressure" (at low RPM), or "substantially less than required water pressure" (at higher RPM's).
We dealers are not "privy" to the specific calibration parameters... but I'll give you a couple of "experience examples":
Engine #1 running at idle speed, maintains .7psi water pressure when the thermostats are open. Temperatures are good- no faults are registered while warming up. The engine is taken out for a hard run... and brought back to idle speed. Water pressure drops to .1psi at idle... and remains below .3 psi for 60 seconds. Engine temps are fluctuating between 150-160 degrees. At 60 seconds or so, a fault registers for low water pressure. The customer raises the engine idle speed, the horn silences, the water pressure increases to about 1.5 psi @ 1000 RPM, the fault becomes "inactive", and the customer goes on with his run. This particular scenario was found to simply be a water pump impeller that, over time, had "taken the shape of the housing", and become "inefficient". Replacement of the impeller, gaskets, and impeller plate brought idle water pressure back into the 1-3 psi range at idle.
Engine #2: 2.5 psi at idle speed. Engine temps all good. Running on plane at 4500 RPM's: 11 psi and good temps. WOT: 7.5 psi and temperatures climbing. Two faults triggered after only 30 seconds at WOT: Low Water Pressure and Starboard Overheat. Engine Guardian became active- limiting available power to 30 percent available. The boat came off plane... water pressure stabilized, temps stabilizied, the faults became "inactive", and the customer could again accelerate to WOT. Now the whole process repeats again... with similar results. This particular scenario was caused by too high an engine mounting/running height- the upper water intakes were allowing air to enter the intake side of the water pump, aerating the coolant, and resulting in decreased water pressure, water flow, and volume. Solution: Lower engine mounting height, or plug upper side water intake holes (three were plugged in this case). The water pump was changed also, simply due to a "high count of low water pressure faults"... and impeller was found to be moderately worn.
I could go on and on... but these two should give you the "general idea". Engine Guardian becomes active to protect the engine from "impending damage"... and will usually become "inactive" when the PCM perceives the issue to no longer be present.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Don, on my 300X when low water pressure guardian hits in it don't reset till either key is turned off then back on or till placed in nuetral. The temp guardian will go back off after temps get to lower range, usually after the boat sits back down, so I usually shift to nuetral anyways to be sure it has reset to full power...
Love the Guardian system, I'm sure it has saved many motors!!
You're right, Lou!
Although Guardian varies slightly from one engine to another, in most cases, you must drop "below the Guardian Limit" in order for it to reset.
And there are circumstances where the key must be cycled to reset the fault.... that's a whole different lengthy discussion titled "sticky and non-sticky faults".
IMO... Engine Guardian is one of the best improvements added to Marine Engines during my "short career span".
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Don, Lou, Eli, thanks for the info on this subject. I have gone into over temp guardian mode but have never seen the low wp mode, this is probablly because when it happens its for a very short period of time and I make an adjustment in engine heigth or trim to correct the issue. As I recall when the motor was on the techs computor the starboard side read 175 degrees and that had set of the fault alarm.
Don, how do you get time for BBC and still get any work acomplished this time of year. It just amazes me when I read your posts and the amount of thought and time that goes into them. I have printed some of the sticky's and try to remimber alot of the other information. I had no idea there was a low water pressure fault until this morning but it makes sence.
Thanks for your time and patience with all the questions and answers your involved in. The information is truly valuable.
Dean
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Strokerdean »</TD></TR><TR><TD CLASS="quote">Don, how do you get time for BBC and still get any work acomplished this time of year.</TD></TR></TABLE>
Lots of early mornings, and late evenings.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Don: Thanks for your detailed info. My question was aimed particularly at the WOT water pressure to engine temp parameters.
So at WOT 5800+ RPM's at about 155+ degrees and climbing I should be looking at bringing the temp down to avoid triggering a fault code? Furthermore this fault code is triggered but has about 30 sec till it goes into guardian unless the temp drops to below the trigger temp. If that happens the motor clears the trigger, resets and no fault or guardian is activated?
Eli, I think 155 it too late you have to be watching it too close to get the motor back down and water recooling..
If I see 150+ I bring the motor down and slow down a little to drop the rpm's.. I know the faster ya go the better the water pressure, but also the more rpm's the closer you get to the treashhold quicker.
If I see 140 I hit the trim up and see if it changes the water pressure, if not I tap the trim back down and tap the motor down also..
I agree.... if you see 155+ at WOT, you've got some big problems (remember, we're speaking specifically of the 3L High Perf motors here.... NOT 2.5L product).
The length of time needed to set Guardian (due to a fault) can vary, depending on the "severity" of the fault. Anything from 6 seconds on.....
Once Guardian is active... you must "reduce throttle below the Guardian Threshold (or limit)" before anything will improve.
It helps if you think of "Guardian" as a "sliding or moveable Rev Limiter".
By the way... to reach 155 "and climbing" at WOT... you would pretty much HAVE to have a water pressure problem.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
What Lou said is exactly what I have been doing, i'll watch the gaugr and when it gets to 140 trim up, if no change then trim back down and lower the motor. This seems to allow enough time to keep the alarm off and out of guardian mode and the temp below 150. Lou is also correct on having to watch the temp gauge very closely, I monitor both, wp and wt when making a run for a big ###. I guess I should have talked to Lou befor but was able to figure it out on my own.
As I stated before, there is a ton of information to be found on this board. Thanks again.
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