Baffled - 2002 200 EFI Smartcraft Motorola ECU overheat at 5000 RPM plus

[crankbearing]

Hey All,

you can drive this motor all day long at 4500-4800 with no issues stays right around 138 to 142 or just below 3/4 on a Teleflex premier guage. anything at 5k or above for more than 3 minutes temp will rise and guardian will kick in and alarm sounds.

It had an overheat problem I took it in a while back. To date here is the process. on muffs from Motor cold on DDT or meds it comes up to temp about 20-25 degree apart if let run long enuff they will even out to within 3-4 degrees. water pressure is 3-5 at idle 15-20 at max rpm. This motor has been on a Bass Cat Pantera, charger DL and finally my Virage same problem.

Stock lower replaced complete water pump kit below gasket as well, replaced thermostats, blew out all passages ran water up the tube and flushed in reverse. same problem. Replaced Poppet complete same problem. removed powerhead and rebuilt exhaust plate no signs of blockage or bad gaskets - same issue. tried other sensors in each head.

replaced divider plate gasket and divider seal - same issue, replaced head O-rings (no diverters in block) same problem.

placed powerhead on a promax mid installed a sporty water pressure is 25+ at high rpm but same problem.

replaced both heads and the divider plate - still the same problem.

I see ZERO signs of water on the plugs, Zero signs of water in the exhaust cavity when I had the divider plate off both times. compression is 125 on all 6 and it runs like a top.

I have converted it to 260 cooling just to try it but have not gone to the lake yet. I am starting to wonder if the 12v oil pump is weak at high rpm. Not sure what else to try.

[crankbearing]

also tried with no thermostats and again with 1/8 washers - same issue.

[Go Time]

It certainly appears to be isolated to the powerhead and the water pressures seem normal. Going lean can build temps. Check your fuel rail pressure while running WOT and see if it falls off. Just a Wild Azz Guess.

[crankbearing]

I was just looking at the parts diagram from the previous serial group engine and I think I may have found an issue. I use the mercury complete poppet valve kits and in the kit it has the new black spring WITH a white washer (poppet washer it is called on the diagrams) the washer is used on the previous serial group 200 engines but when I pull up the poppet diagram for my serial group IT does not show that washer being used. Could that washer really restrict flow at high rpm?? This is the only thing I can see different in the poppet assemblies.

[crankbearing]

I converted it back to stock cooling replaced the poppet without the washer, that did not fix it. I got my hds 5 installed today and hooked up the merc gateway. With 1/8 washers the temp data is showing 120-125 at 5k plus on the hds5, yet the alarm is sounding and the mechanical gauge is saying it is over 3/4. Fuel pressure is 39-42 all the time.

[HydroSkreamin]

Crankbearing, have you looked with a DDT or other tool what the ECU is reading for block pressure? The EngineGuardian not only looks for temperature to warn of overheat, but if the block pressure sensor is reading erratically or improperly, the lookup table for Guardian may be reading that the block pressure input it is getting will not sustain steady state operation. I saw this on an Opti of the same generation, and it turned out to be a bad sensor, but hadn't failed open or grounded, so it was reading, but the values were not correct. Hope this helps, everything else sounds to be in order. That 3-pin connector should be wiggled while you are on the DDT or other tool to see if the connection is OK for good measure. Also, is the block pressure sensor Tee'd with your mechanical gauge? Did it get plugged back in? Good luck.

[muskamoot]

Cut two turns off the poppet spring and try it.

[tony97gt]

Maybe your ECU is f'd up. Find another one and swap them to see if it's the issue. I just had an ECU go out in my 2005 200 EFI and it was making the engine run very very rich, idle at 2k, and couldn't accelerate. I know it's different symptoms but maybe you have an ECU problem.

[crankbearing]

thanks guys. yes I have had the ddt hooked up as well and the block pressure has always seemed stable (yes mechanical is t'd in at the bottom of the divider) although I did not have it hooked up with me while driving, I have an sc5000 system view race version and 1 port left open on my junction box, I will try and take it with me as well just to compare notes with the hds-5 I can also take the ddt. Tony I was starting to think along those lines as well. I found an 03 down on one cylinder locally yesterday and I am waiting to hear back on it. This is a real sleeper and with all the money in time I have in it, I could never get out of it what I need once it is fixed. So I might just keep it; it's under a 95 2.5 EFI pro max cowl and on a 20" bass pro-max mid with a fat shaft sporty. I have my 30 DR4 performance prop on it right now and it is turning the heck out of it. I just wish I could hold it to the boards once to see what it will do. This motor ran 72 on a bass cat pantera with two guys and full livewells and a 25 trophy plus. There has not been very many of these that have me scratching my head this bad I am glad we have a sounding board, I have to fix it now it's driving me nuts.

[Go Time]

LIke hydro suggested above, did you check to see if the alarm sending unit is the problem? I had that problem run me in circles once.

[tony97gt]

If the alarm is defective I don't think that could force the engine into guardian though, would it? Wouldn't it just make the alarm sound but not go into guardian?

[Go Time]

Good point Tony, I missed that the engine is goning into gaurdian mode. The DDT should tell you exactly which head (Port or Stbd) is giving you the alarm and if there is a big difference in the port to Stbd in the temps, I'd swap the senders and see if the problem move with the sender.

[crankbearing]

I checked the pressure sensor this morning with meds it seems fine. I checked faults and freeze frames and there is no overheat codes at all anymore. The last one was stbd at 340 hours and now the motor has 347.7 hours. The last two freeze frames were guardian due to Batt overvoltage at 16.89 at 5149 RPM temp was at 122 and a batt overvoltage at 16.89V 4550 rpm temp was at 125. Could the overvoltage be driving the mech temp gauge up, It is a brand new premier teleflex I am using the merc sensor in the head instead of the sensor that teleflex supplies with the gauge. Overvoltage is strange it never had shown that code before. Could the pro-max cowling which is tight to the alternator on that side causing the alternator to heat up too much. It is a brand new marine master 24M7 battery less than 3 months old.

[Go Time]

I'm guessing the gage is analog (not digital) electric (not mechanical) and a significant voltage increase can cause the gage to read in error. Probably a bad voltage regulator.

[crankbearing]

I ran it for nearly an hour with a little rpm on it the voltages on ddt, hds-5 and dash gauge never went over 14.2. I put the cowl back on the motor and ran it some more it got hot to the point I could not put my hand on the cowl for very long around the alternator area. I removed the cowl and removed the plastic cover that Merc installs on the powerhead and re-installed the cowling the temp was quite a bit less in that area. I have a new alternator on the way that I will try out tomorrow night. temps are right around 128-138 at idle with washers. The poppet is working perfectly I bring up the rpm to and pressure climbs and I can watch the poppet open and the pressure drop off and stabilize. lots of hot telltale.

really the only weird thing is the ddt is saying the port head is warmer than the stbd head by 6-10 degress yet the stbd head feels much hotter to the touch. I will check them with a pyromter tomorrow to be sure. The only overheat code it showed was stbd bank at 340 hours.

Thanks for the help guys.

rgds,

Dave