Evinrude 90hp Outboard breaking down

[Refugee]

Sometimes, and more than likely when under load from towing a tube, my outboard seems to stop running on 1 or 2 cylinders.

I believe, and am open to other suggestions, that it is either the powepack or ignition coils. These are quite exy so want to buy the correct unit. Is there a way of testing if its one or the other?
I cannot find out if its 1 or 2 cylinders as that will mean travellin without the engine cowling on which is too unsafe for my little'ees running around.

I suppose I could take it to a mechanic however I like to use these experiences to learn (an am also a tightwad).

Thanks,
Shaun

[Noelm]

first thing first, remove the plugs and have a look at them, are they all the same in appearance? do a compression test while you have them out, can you run on a complete remote tank and hose with fresh fuel (just to be sure) and before we go any further, run out and buy a genuine manual for your motor, it will have all the touble shooting steps for the ingnition system and how to isolate a fault/component.

[Kero]

What year model is it? I've got an OMC service manual for a V4. I'm happy to scan relevant sections and email to you.

[Noelm]

just as an educated guess, the coils are unlikely, having a couple go dead at the same time will be not too common, an easy test is to look at the plugs when it is/has been missing, the dead ones will be black and oily, it is a simple step to swap the coils with the other good cylinders to see if the fault moves.

[Noelm]

a service manaul will be neded for proper trouble shooting, so far we dont even know what model it is, if it is dropping spark on one or two cylinders, we need some help, so we can help you.

[svranjic]

Compression test first then that way you know the motor is sound.

Like everyone has said a proper workshop manual will help enormously. Mine only cost 30 bucks from the US but it has helped me go over my motor with a fine toothpick and makes life that much easier.

If you have an inline spark tester I would hook it up to each lead and ensure you are getting spark to jump a 7/16" gap.

Check spark plug condition and gaps - if your unsure replace plugs.

Check the condition of leads too. Do you know which cylinder/s are missing?????

If both of those things go ok then either you have another issue or your spark problem is only occurring intermittently and whilst under load.

If its not spark or compression start looking at fuel / carbies.

[tunaticer]

Sounds to me like it is the engine going into slow mode most likely due to a heat problem. Disconnect the heat sensor wire if the motor throws no steam normally and put the motor under load for a few minutes, this should stop the the SLOW mode starting up if the heat sensor is faulty. If the motor shows signs of heating under load change the impellor and flush the journals and remove the thermostat and check it still works ok. Often the ports in the thermostat can clog with grit as well.
Does not sound like ignition problems or fuel supply problems to me from what you have described.

[Refugee]

Thanks all. My Telstra line has been down so no Internet. Appreciate the replies. Taking the advice from here I have found a workshop manual and will start deciphering the troubleshooting areas now.