1988 searay mecury 135 no power at WOT?

[Donny Mize]

Motor idles fine, revs fine without being in gear, even compression all six cylinders, fuel flow to carbs is good, fuel is good and I just replaced a burnt rectifier. Motor will not plane off or get above 2500 rpms any more and seems to have gotten progressively worse the more its run.
I have read about switch box and stator problems with this model and year motors, would a burnt rectifier have damaged or be a indication of damage to either the switch box or stator?
Also I am pretty sure my water pump needs rebuild, would low water pressure cause my problem?
Thanks for any help.
Don

 

[hkeiner]

Re: 1988 searay mecury 135 no power at WOT?

Use a timing light or DVA meter to check for failed ignition on one or more cylinders during engine bog. If the ignition is failing during engine bog, you can troubleshoot the ignition system further by doing some bench tests. A shop manual for your motor will describe the various tests. Do not replace ignition parts on a hunch. They are too expensive to replace unnecessarily.

By the way, reving the motor out of gear does not indicate much, as there is no load on the motor and the spark could be failing only on the high-speed ignition circuit anyways.

 

[emckelvy]

Re: 1988 searay mecury 135 no power at WOT?

Here's some good troubleshooting links:


http://www.outboardparts.com/troubleshooting/troubleshooting7.htm

http://outboardparts.com/mercury/troubleshooting/troubleshooting10.htm

http://dolphinmarineservice.homestead.com/ign5.html

http://dolphinmarineservice.homestead.com/tech.html

http://www.boatpartstore.com/mercreadings.asp

http://outboardparts.com/mercury/troubleshooting/troubleshooting11.htm

I'd look very carefully at the resistance of the High Speed and Low Speed stator windings, if they're off, the stator is probably bad.

You can rule out any issues with the trigger via resistance checks, too. Wiggle the trigger wires to make sure there's not a hidden break somewhere in the wiring.

Ign coils can be resistance-checked, and also physically examined for cracks/arc marks.

HTH & let us know what you find........ed

 

[Donny Mize]

Re: 1988 searay mecury 135 no power at WOT?

OK...here is the update.
My service manual says that the resistance of the stator red lead to power head ground or black stator lead should be 90-140 ohms...I got 10!
Bad stator?
My manual also says the trigger should test between 11-14 ohms at brown to white, white to violet and violet to brown...i got 1.86M ohms...yep I read it right!
Bad trigger too?
The tach bounces around too...tach runs off stator right? Another indication of bad stator?
Let me know what ya'll think ASAP I don't have a lot of confidence being first time doing this so I'd like confirmation before I spend another 300.00 and thanks for the help.

P.S.
I just rebuilt the fuel pump and water pump and for any one with a little mechanical ability and paitents its not hard at all.