Unofficial 587,657,717 Mpem troubleshooting guide

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Random Sutdowns:

1.Check all fuses.
A.Mpem fuse is blown. Your Mpem may have a shorted diode causing high current draw.
Using a DVOM, check for reverse current flow. (black lead to mpem fuse, red to ground)
If mpem fails test, repair or replace Mpem and program key.

B.Charging fuse is blown. The rectifier has shorted causing it to draw high current.
Check the output of the red wire while the engine is running. If negative or low voltage is
present, replace the rectifer and check the stator wires (yellow, yellow black) for a short to

C.An accessory fuse is blown. Determine which accessory no longer functions and
troubleshoot the malfunction.
2.Check spark plugs for correct type.
A.Seadoo Magneto ignitions REQUIRE the use of a resitor type plug. That is what the R
in BR9ES on your plugs mean. (not racing) Non-R plugs are often pushed over the counter
at parts stores by accident or carelessness. Use of Non-R plugs will result in voltage spikes,
that will cause random Mpem shutdowns. This is normal operation for the Mpem, it is a
function designed to prevent electric shock of the operater, due to high voltage at the DESS
3.Check all connections
A.Connectors can become corroded and cause intermittent problems. Clean, inspect, and use
white lithium grease to prevent future corrosion. Bombardier uses connectors as ground
busses. They look like a connector with a cap. Remove the cap, and a metal strip will be
present, this is the buss, maintence as neccessary.

B.The DESS "key" is actually a ROM chip. The outer ring on the DESS post provides the chip with
ground. The inner contact connects the Mpem to the ROM chip. Saltwater users may need to
clean these contact points with an eraser, and possibly wipe with a mild lubricant.
4.DESS Post
The DESS post is nothing more than a magnetic switch, and two contacts. The "key" is a
magnet, and a ROM chip encapsulated in a marine kill switch lanyard. The Mpem "reads" the
ROM signature, when it matches one of it's programed signatures, it enables accessories, the
start stop circuit, and ungrounds the ignition circuit.

A.With the "key" on the post, check the continuity from the black to black yellow wires. The
ohm meter should read less than 2 ohms. Tap around the post to ensure the connection
does not break or change.
The rectifer has the job of converting the AC produced by the stator, into regulated 13.5-14.8VDC. Failure of the unit can lead to shorts, or overvoltage. Either may trigger Mpem shutdowns or resets, causing intermittent ignition failure.

A.Check the output of the red wire while the engine is running. If negative or low voltage is
present, replace the rectifer .

B.Static or non-operational tests are not valid due to the regulator circuit.
The stator is the part of the magneto assembly that generates AC power. Shorting can cause
regulator/rectifier failure.

A.Check the yellow to yellow/black wires, they should read .05-6 ohms.​

7.Ignition Magneto
The magneto produces the power for the ignition system, completely independent of the
charging/battery system. (not counting the shared ground) The Mpem controlls ignition by
grounding the generator and ignition coil.

A.Measure the black to black/red wires. Ohm meter should read 40-76.​

8.Neutral Safety Switch
Located on the bottom of your shifter, this is a normally open switch. If it fails in the open position, RPM will be limited to 3,500 RPM by the Mpem, as it belives the boat is still in neutral. The boat will also start in FWD or Reverse. If the switch fails in the closed position, the Mpem will not allow the starter to engage in any shifter position and will sound 4 beeps.

A.Check the red/white wire at the Mpem to ground. It should read OL or infinate ohms in
neutral, and less than 2 ohms in FWD or REV. If the switch fails, remove the shifter and
inspect the switch. Retest at the switch, same specs, replace if necessary.​

9.Start Stop Switch
This is a normally off, on/off switch. Tap around it during testing to ensure the readings do not
change. A stuck switch may cause the starter to remain engauged during engine operation.
The Mpem will remove ignition at that point. If the button remains stuck, you may not be able
to restart the engine.

A.Check the yellow/green/red wire at the Mpem. It should read OL or infinate ohms to
ground. Press and hold the switch, it should read less than 2 ohms to ground.
10. Low battery/batteries.
The mpem will reset if voltage drops below a predetermined threshold. This may happen if
voltage drops during initial starting on a weak battery. The Mpem will reset, and respond to
the start command with one long anoying beep.

Will edit as needed. Best of luck to all.

nice check list.
I think it will work for 787 engines too.

Can the key &/or post be cleaned or tested in any way
nice check list.
I think it will work for 787 engines too.

Can the key &/or post be cleaned or tested in any way

The 787 uses an actual stator with magnetic pick-up and digital ignition. It is a 7 wire system that works diffrently than the 4 wire magneto system. I may do a 787,951 guide later. I chose this system because it affects the widest variety of years/models, and I've already had my round with it and won. ;)

For question two, see point 3,B

Have lurked here many many moons and cant ever remember posting anything but have fixed my Sportster 717 boat and skis just by reading threads like this one.

I'd like to reinforce #3 above. Even if it looks OK to the eye, in the older stuff that I work on, sometimes it isn't. Clean those posts. These motherboards (MPEM etc) use tiny connections (wires) in and out that very little corrosion can stop your machine from running - without being visible to the eye. What's worse, is that tiny corrosion can mimic real engine problems. Save yourself from pulling that engine and meticulously clean your connections first, especially if it is an older boat/ski.

Great thread. Thanks for this and the other sticky posts that keep us silent readers from having to post.
Great thread. Thanks for this and the other sticky posts that keep us silent readers from having to post.

Thank you for the feedback! While we like to help with out the same questions being asked time and time again it is also important for forums to have feedback and posts from the lurkers like your self. Thank you for taking the time to sign up and post!
Need some help with a 1997 Seadoo Speedster.
None of the gauges work at all. Recently bought this used knowing the gauges were inop.
Fuel sender has continuity, fuel gauge lights work but no supply voltage to any gauges.
The wiring diagram shows a "gauge relay" and 5 amp fuse somewhere within a "micro-controller".
Anyone know what that is? is that the MPEM?
I'm also trying to find where the tach gauges are connected to on the engine.
The 1997 Shop Manual doesn't specify.