Logo
FULL SITE MENU

1990 90hp Mariner 3 cyl oil inj won't accelerate past 3200rpm

M

Monson02

New member
Finally decided to try asking my own question instead of diagnosing through what others have posted. Idle is great, relaxing cruise speed is great. Cleaned and rebuilt all 3 carbs, rebuilt fuel pump, replaced main fuel line and bulb, replaced fuel filter, replaced plugs. From what I've read it seems like it hits S.L.O.W mode, just will NOT go above 3200 rpms, guessing tach is off since limp seems to hit around 2500. I unplugged temp sensor while on water and no change, tell tale had great constant flow. Unhooked fuel pump and squeezed bulb to see if fuel is getting past the diaphragm but all was good there. Ran separate fuel tank to see if air flow was an issue, no change. Compression tested all 3 cylinders and read out 117psi across the board. I'm sure I'm forgetting something but I'm hoping one of you will have the right answer. Thanks!
 
Which of the two would be better to start with? Just so I learn something..... Why stator or switch box? Power from the box not enough so replace it? As for the stator, I have no clue what that does.
 
Most common with these engines is a stator problem. You can easily check the resistance of the high and low-speed stator windings with a meter.

Check out the troubleshooting information at CDI Electronics:

http://www.cdielectronics.com/support/

I'd recommend the "download and print" option for the manual, it's a lot easier to deal with than the online version. And you can easily print out the troubleshooting pages for handy reference.

HTH................ed
 
Also, I just called mechanic and he said I had to get the Mercury Quicksilver stator and not off brand cuz it doesn't get along or something. Any truth to that? Why wouldn't an aftermarket work?
 
Monson02 said:
Also, I just called mechanic and he said I had to get the Mercury Quicksilver stator and not off brand cuz it doesn't get along or something. Any truth to that? Why wouldn't an aftermarket work?
Click to expand...

IMHO your mechanic is ill-informed. Far as I'm concerned, the CDI Electronics replacement stators are as good or better than the Merc factory parts. And usually a good deal cheaper. I've installed a lot of these and have never had one fail.

But be sure you're not throwing good money after bad, it's very easy to disconnect the red and red/white, blue and blue/white stator wires from the power pack and do resistance checks. If the ohms values are off (especially if they're high), the stator is definitely bad.

HTH..........ed
 
Thank you for the clarification, wish I was closer to a few more shops so I could choose the better. Kinda got me by the you know what..... Thanks again I appreciate the help. On a side note, how much of pain would this be for me to do on my own? Electrical is not my strong point but I was able enough to disassemble and rebuild my carbs.....
 
The CDI Electronics ignition troubleshooting manual has a section for 3-cyl ADI Mercs such as your motor, and has resistance values for the stator windings. If you can operate a $9.95 Sears VOM, you can take these resistance measurements. As mentioned previous, you do need to disconnect the stator wires before taking resistance measurements.
 
I will definitely try that, how bout replacing the stator itself? Or is that gonna be something out of my league? Read something but having a harmonic balancer puller it something to remove the flywheel and even heard of having the bolts tightened to a certain psi....
 
You'll need a flywheel puller and a torque wrench to do the flywheel.

This cheap flywheel holding tool is pretty handy to have, too:

https://www.homedepot.com/p/Powerbuilt-Flywheel-Turning-Tool-648455/204505230

You'll need it to hold the flywheel when loosening and tightening the flywheel nut.

You can get an inexpensive, adequate-quality flywheel puller on eBay.

The $153 Mercury factory tool, P/N 91-849154T1, is sold here as well:

http://www.marineengine.com/newparts/part_details.php?pnum=MER91-849154T+1

The $16.00 eBay puller should do the job just as well, it wouldn't be suitable for a shop that uses one every day but you'd use the puller very infrequently I reckon. The seller "mbsmfg" has a lot of good feedbacks on the puller.

You should have a manual for working on your outboard, this will have torque specs for your flywheel nut. And a good section for flywheel removal. If you can't find the factory manual here for your motor, the Seloc line of manuals give sufficient direction to get the job done.
 
While beginning to test wires, I noticed there was a nylon nut that was loose and spinning on the pole of the rectifier. The rectifier also looked a tad melted. Since the nut is spinning that leads me to believe not a strong connection, could that be a culprit or still stator/switch box?
 
Monson02 said:
While beginning to test wires, I noticed there was a nylon nut that was loose and spinning on the pole of the rectifier. The rectifier also looked a tad melted. Since the nut is spinning that leads me to believe not a strong connection, could that be a culprit or still stator/switch box?
Click to expand...

As I recall, the troubleshooting guide says to replace the rectifier, then test run to see if the problem is still there. If it is, then continue the troubleshooting.

I would replace the rectifier in any case, as it sounds bad, but would also be sure to check that stator resistance to see if it's OK or not.
 
Back
Top