Driving me crazy......

[ahifever]

First off please forgive my ignorance, I'm not a mechanic but I am fairly capable of doing a lot of work on my outboards and Sorry for the long post.

I have a 1986 90hp yammie that has been acting up lately and its been very frustrating. Here goes, first problem is the engine won't always shut off when the key is turned off, next is with my analog tach, lights work but the needle doesn't move. Last time out it would work intermittently. Also, the engine will sometimes shake violently above 2500 rpm's. If i keep it below 2500 it runs smooth. Obviously(I think) it's some kind of electrical problem. I ordered a new engine harness and hope this will eliminate at least some of these problems when I install it.

Would a bad stator assy. or pulsar coil cause any of these problems?

Thanx in advance for your feedback
Ikaika

[Ken]

Ikaika,
I would replace that ignition switch also, along with the wiring harness.
If new connections to tach does not fix problem, then it's probably bad tach.
Good luck,
Ken K

[scotty]

Here is a long shot.... but electrically it is worth trying. Disconnect the tach from the wiring harness. And disconnect as much of the tach's wiring from the harness as you can. It is possible for the ignition to get a timing signal via the tach circuit and that could cause it to keep running.
scotty - taking a long shot....

[ahifever]

Thanks for the feedback guys!

Ken,

I just installed 2 brand new 703 remotes a couple months back, do you think that the one acting up could be faulty or is it more likely something else?

Thanx
Ikaika

[Ken]

Ikaika,
If your motors ran ok for a while after installation of the 703 remote controls, then I would not suspect either control going bad now.
I would replace that ignition switch on the motor that does not shut off sometimes.
Motor shaking violently above 2500 rpm - I would not suspect any of the coils of the stator.
Sounds like rpm reduction mode due to overheating, but you should hear the alarm horn going off at same time.
Check to see if thermo switch sounds the alarm. Trace the two wires that lead from the thermo switch that is mounted in the head assy - should be near the top of the head. The wires should lead to a pair of bullet connectors about six inches away from the switch. Disconnect the two bullet connectors, and with the ignition on (motor not running) short together the two wires that lead back to the CDI. The alarm should sound.
If it does not, then the alarm and/or associated wiring is bad, and I would suspect the motor is going into rpm reduction due to overheating. If it does sound, then I would suspect fuel starvation problem - fuel pump would be suspect.
Good luck,
Ken K

[ahifever]

Ken,

I tried the alarm and it is not sounding, I did replace the impeller about a month ago and the water is flowing strong. It does seem like its going into safe mode but before my last trip out I changed the main ground wire and it started to run fine and about an hour into the trip it started to shake again. I get home and just the other day I find that the ground wire at the battery terminal was a little loose, so I tighten her up and now its running fine on the earmuffs. Could a bad ground actually cause these symptoms?

Anyway, I will be replacing the ignition switch like you stated and I'll let you know of my results. My new engine harness is on backorder so I'm not sure how long it will take to get here.

Thank you very much for your help
Ikaika

[Ken]

Ikaika,
You bet, a bad ground in any electrical system can cause all kinds of weird symptoms.
I would still suspect that 90 is going into rpm reduction mode. Next time out, if it starts to shake like before, shut the motor down and remove the hood. Disconnect one of those wires to the thermoswitch, tape it or tie wrap it so that it does not short out. Re-install the hood and run the motor to see if that keeps it from shaking above 2500 rpm - if it does, then that motor is overheating, or at least the thermo switch thinks it is. Do not try to run very long above 2500.
When back in port, remove that thermo switch and test it in a pan of heated water - use an accurate thermometer and monitor the resistance between the two leads - you should see contact closure, zero resistance, at around 185 degrees. I have personally seen one close at 130, giving a false overheat condition.
Once you determine that the thermo switch is doing its job (or not) then you need to find out why the motor is overheating.
You say you have recently replaced the impeller of the water pump - so I will rule that out. Have you checked the pressure relief valve?
The PRV is designed to open at around 20 psi to relieve over-pressure in the water jacket. It can get stuck partially open from salt/sand/mineral deposits or broken/weak spring, and dump cooling water out the relief holes, thereby bypassing the water jacket. Check it out.
If you don't already have one, get yourself a Yamaha shop manual - go to www.yamahapubs.com to order online. It's expensive, but will pay for itself.
Good luck, and let us know what you find out.
Ken K

[Ken]

Ikaika,
In my previous post I failed to mention that a stuck thermostat could also lead to your motor overheating. If you do determine that the thermo switch is good and doing its job to indicate an overheat condition, then you need to also check the thermostat in addition to the PRV. They can get clogged with mineral deposits and fail to open all the way, thereby not allowing enough cooling water to flood the water jacket of the head.
You can remove and test the thermostat in a similar fashion as the thermo switch - in a pan of heated water. It should open fully at a temp of approx 135 degrees. Again, the Yamaha shop manual describes this testing also.
Good luck,
Ken K

[ahifever]

Thanks for all the info Ken.

I was told that Here in Hawaii mechanics just remove the thermostats, I guess because the water is so warm here. Sure enough when I removed the thermostat there was nothing in there. There is one other problem I'm having, It seems that the top cylinder is not firing. I tried several things like swapping coils ,plugs even cdi unit and still when I remove the spark plug wire when the engine is running theres no difference. When I remove the other plug wires the engine hesitates.

Huhhhh.....If it's not one thing it's another. It may be time for some new engines. Around here we have a saying that B O A T stands for
Break Out Another Thousand. It sure seems that way in the harsh saltwater environments here in Hawaii.

Anyways, Thanks alot, I appreciate all the help.
I'll let you know what Happens.

Ikaika

[Ken]

Ikaika,
Man, I can spell your name now w/o even having to go back and look at it!
Yeah, B O A T stands for the same thing over here also - you gotta' love out sport to keep shelling out the money.
On that top cylinder not firing, pull the spark plug wire and attach to another spark plug and crank the motor to see if there is any spark.
If there is not, then you obviously have ignition problem. If there is spark, then I would do a compression test - do it on all three cylinders. If that top cylinder is way out of line from the other two, then I would suspect worn or stuck rings. If compression checks ok, then I would suspect fuel problem.
Your outboards are pushing 20 years old now, and depending on how much they have been run, they are probably due new rings, head gaskets, carb overhaul, and fuel pumps.
Let us know how you come out.
Ken K

[ahifever]

What's up Ken?

It's been almost a month now since I posted this topic, I finally received the new harness today and installed it, and guess what? it seems to have solved the problems. I won't be totally sure until I have a chance to take her out on the water, but it's running great on the muffs and all seems well.

Thanks for all your help! Now hopefully the gas prices don't go up to $4 a gal. or I'll never take her out again. lol.

Ikaika

[Ken]

Ikaika,
Hope your problems are fixed - now let's hope that these fuel prices come back down a little . I have personally cut out all non-essential traveling - am saving my money to buy fuel to go fishing for the fall season. We are paying about $3 a gallon here .
Good luck [img]smile.gif[/img] ,
Ken K