90HP Mariner No Power at full Throttle

[4thekids]

92 Mariner 90 Hp Outboard, Starts and runs slow just fine, When Throttle is put to full, it seem to lose a cylinder (Bottom cylnder of the 3 cylinders). If only 1 person is in the boat, It will start acellerating slowly then like a switch it kicks in with no problem after about 1 minute and runs fine until brought back to an idle, then the same happens. If there are more people in the boat or pulling a tube, it will not kick in. All spark plugs are OK, the coils check out with a ohm meter OK. $$ are very tight so need a good diagnosis to repair. Is it the CDI, or what is a trigger? or could it still be a coil even though they all check out the same?

 

[sylvaing]

Re: 90HP Mariner No Power at full Throttle

I had the exact same problem last year.

I ended up changing the switchbox, trigger, stator and voltage regulator. IIRC, some parts have been modified in a way that other parts needs to be changed as well. I think that was the case for the stator and the trigger.
I think it ended up costing me around $500. The engine has never been run as smooth as it is now since I got it.

See thread

http://forums.iboats.com/showthread.php?p=1780459#post1780459

Edit: Get the manual for your engine from this thread:
http://forums.iboats.com/showthread.php?t=309079

Should help you diagnosing the problem...

 

[4thekids]

Re: 90HP Mariner No Power at full Throttle

Thank you Sylvaing.

Now the update, all 3 coils have been checked out the same. The Stator was replaced 8 years ago with the voltage regulator. Checked the Stator, and all resistance readings are good per the spec.

Being it is the same cylinder droping (always the bottom cylinder) and the coils interchanged with the same result. Would the problem be more specific to the switch box?

Does the switch box control weather the engine runs on 2 or 3 cylinders?
Thank You.

 

[sylvaing]

Re: 90HP Mariner No Power at full Throttle

Found this link that might be of some help to you...

http://www.marinepartsman.com/ELECTRICAL-IGNITION-troubleshooting-in-Mercury-and-Mariner-outboards.html

Specially :

"OUTBOARD ELECTRICAL & IGNITION TROUBLESHOOTING TIPS

1. Intermittent, weak, or no spark output at two spark plugs usually indicates a bad TRIGGER.

2. Intermittent, weak, or no spark output at all three spark plugs usually indicates a bad STATOR or SWITCH BOX.

3. Intermittent, weak, or no spark at any one spark plug usually indicates a bad SPARK PLUG, COIL, or SWITCH BOX."

So since you ruled out the plugs and the coils and only happens to one cylinder, this leaves the switch box like you said.