I am running a last-gen 2006 200xs SS on a 1995 GSE. I put a Smartcraft on it last summer.
At that time, I was chasing down some electrical issues (ultimately it was the TPI) and so I bought the Merc shop manual.
A couple days ago, I'm out running under 4,000 rpm just leisurely cruising and BEEEEEP a continuous alarm sounds. The Smartcraft flashes a bell icon and a thermometer. Oh no, I'm thinking...overheat alarm. Which it was...although puzzling to me at the time and that's the reason I'm sharing this.
A quick cycle through the Smartcraft functions into engine temp yielded only 87 degrees...Now I'm really confused because the thermostats don't even open til 143F!
The motor also did NOT enter "guardian mode" (severely restricting rpm and power as a self-preservation feature) which I also noted as strange, if this was a "real" overheat.
I also noticed the tell-tale "pee stream" was no longer its usual laser beam affect; it was still present but curved and saggy.
I decided to risk it by opening her up in an attempt to get more water thru the system - this worked and the alarm quit, but whenever I slowed down, back to the beep.
Trailered the rascal. Consulted with Ace Merc tech friend who said that the tell tale is fed directly off the air compressor's cooling water flow output. Now...Coming from your basic 260, 280 and Drag motor 2.5's, the air compressor was something I'm not used to. It develops the pressure needed to inject fuel under the DFI operation. I also did not know it needs to water cooled.
I'll cut to the chase, a roadmap to troubleshooting it that fixed the problem and some facts gleaned from the service manual I'll bet many guys who run these motors are unaware of, as was I.
Fact 1: the 200xs uses THREE temp sensors, all constantly monitored by the ECM. They are the same exact part number and each will trigger an alarm if temp exceeds 215F. The locations are port side cyl head, starboard cyl head, and...compressor.
Fact 2: Smartcraft only monitors ONE of the three--port side cyl head.
Fact 3: ECM will NOT kick motor into guardian mode if compressor overheats....only either cyl head.
Using these facts plus a very impressive multi colored foldout water flow diagram from the service manual, it was easy to trace the flow backwards, but a lot different than the old school EFI's. For the relevant point is that the fuel rail injection coolers and the compressor cooler are fed serially by the same hose: an odd-looking affair that works by means of a 3" cylindrical water "strainer" that threads into the exhaust plate on the port side. You must remove the skirt to get to it.
These motors use a pressurized reservoir of water fed by block pressure to squirt water through this debris strainer, up a hose to the fuel rails, then into the compressor and after that, the pee hole.
I removed the strainer. Sure enough! Partially plugged with pieces of tiny sticks, sand, and mud. Cleaned by fresh water rinsing and compressed air. Simple! However, I thought, if this was plugged there may be more crap in that reservoir in the exhaust plate. What to do?
Here's where I went off-road with a redneck engineering plan.
I found me a fitting with same pipe thread as the strainer, plugged it up with a bolt, and hand-threaded it into where the strainer usually goes. I got out my infrared thermometer, as I had no desire to burn this motor up while executing said redneck plan.
Hooked her up to a hose and fired up. Monitored temp of both heads and compressor, the compressor now receiving no water at all. But the plan was to be brief.
Quick checks of temp with IR showed heads cool, compressor heating rapidly (97F after a minute) so I acted fast.
Reaching down to my home-made plug, I realized the net effect of this plan was not just depriving the rails and compressor with cooling water, but to build pressure in that plate reservoir. I rapidly unscrewed the plug with the motor still idling, and she puked her guts out into the driveway, consisting of small sticks, sand, scum and mud.
Immediately ran to helm and killed motor. Reinstalled cleaned strainer into now-cleaned reservoir. Reattached all hoses. Fired up. Laser beam pee stream back, temps all good, no more alarm, launched and ran for 30 miles, all is right with the world.
At that time, I was chasing down some electrical issues (ultimately it was the TPI) and so I bought the Merc shop manual.
A couple days ago, I'm out running under 4,000 rpm just leisurely cruising and BEEEEEP a continuous alarm sounds. The Smartcraft flashes a bell icon and a thermometer. Oh no, I'm thinking...overheat alarm. Which it was...although puzzling to me at the time and that's the reason I'm sharing this.
A quick cycle through the Smartcraft functions into engine temp yielded only 87 degrees...Now I'm really confused because the thermostats don't even open til 143F!
The motor also did NOT enter "guardian mode" (severely restricting rpm and power as a self-preservation feature) which I also noted as strange, if this was a "real" overheat.
I also noticed the tell-tale "pee stream" was no longer its usual laser beam affect; it was still present but curved and saggy.
I decided to risk it by opening her up in an attempt to get more water thru the system - this worked and the alarm quit, but whenever I slowed down, back to the beep.
Trailered the rascal. Consulted with Ace Merc tech friend who said that the tell tale is fed directly off the air compressor's cooling water flow output. Now...Coming from your basic 260, 280 and Drag motor 2.5's, the air compressor was something I'm not used to. It develops the pressure needed to inject fuel under the DFI operation. I also did not know it needs to water cooled.
I'll cut to the chase, a roadmap to troubleshooting it that fixed the problem and some facts gleaned from the service manual I'll bet many guys who run these motors are unaware of, as was I.
Fact 1: the 200xs uses THREE temp sensors, all constantly monitored by the ECM. They are the same exact part number and each will trigger an alarm if temp exceeds 215F. The locations are port side cyl head, starboard cyl head, and...compressor.
Fact 2: Smartcraft only monitors ONE of the three--port side cyl head.
Fact 3: ECM will NOT kick motor into guardian mode if compressor overheats....only either cyl head.
Using these facts plus a very impressive multi colored foldout water flow diagram from the service manual, it was easy to trace the flow backwards, but a lot different than the old school EFI's. For the relevant point is that the fuel rail injection coolers and the compressor cooler are fed serially by the same hose: an odd-looking affair that works by means of a 3" cylindrical water "strainer" that threads into the exhaust plate on the port side. You must remove the skirt to get to it.
These motors use a pressurized reservoir of water fed by block pressure to squirt water through this debris strainer, up a hose to the fuel rails, then into the compressor and after that, the pee hole.
I removed the strainer. Sure enough! Partially plugged with pieces of tiny sticks, sand, and mud. Cleaned by fresh water rinsing and compressed air. Simple! However, I thought, if this was plugged there may be more crap in that reservoir in the exhaust plate. What to do?
Here's where I went off-road with a redneck engineering plan.
I found me a fitting with same pipe thread as the strainer, plugged it up with a bolt, and hand-threaded it into where the strainer usually goes. I got out my infrared thermometer, as I had no desire to burn this motor up while executing said redneck plan.
Hooked her up to a hose and fired up. Monitored temp of both heads and compressor, the compressor now receiving no water at all. But the plan was to be brief.
Quick checks of temp with IR showed heads cool, compressor heating rapidly (97F after a minute) so I acted fast.
Reaching down to my home-made plug, I realized the net effect of this plan was not just depriving the rails and compressor with cooling water, but to build pressure in that plate reservoir. I rapidly unscrewed the plug with the motor still idling, and she puked her guts out into the driveway, consisting of small sticks, sand, scum and mud.
Immediately ran to helm and killed motor. Reinstalled cleaned strainer into now-cleaned reservoir. Reattached all hoses. Fired up. Laser beam pee stream back, temps all good, no more alarm, launched and ran for 30 miles, all is right with the world.
