'RPM Reduction' - 'Slow Mode'

[n2yjc]

My '86 Yamaha goes into slow mode during warm-up then its fine for the rest of the day. I tested the oil level sensors and the temp sendor, even disconected them as a test one day, still goes into slow mode during warm up. Any thoughts?

Thanks - Lou

[jb123]

does your buzzer work and do you have a multi gauge?

[slim]

how do you know its going into slow mode during warm up? are you getting a buzzer? what rpms do you warm it up at? the rpm reduction doesnt kick in till 2000rpm. if your warming up above this you really shouldnt be.

[n2yjc]

Gentelmen, maybe I should re-word 'warm up'. For the first 10 or 15 min the engine ('86 Yamaha 90HP) wont rev over 2000RPM. I have tested the 2 oil sensors and the temp sensor and the buzzer does work. What else besides the oil and temp sensors will trigger the rev limiter? I have studied the wiring schematic and checked all of the connetions involved with these sensors.

Thanks - Lou

[jb123]

1986 and saltwater use, i would then check all ground points if you indeed checked and lubed all harnesses, sounds like you are getting a bad signal.

[jb123]

i did have a pair of 1990 200`s that i cut the over-rev limiter on.... but not sure if yours has one or not.

[n2yjc]

JB123, how did you disable over-rev limiter?

[slim]

if you have it to cut, there will be a gray loop of wire coming out of the cdi most likely out the bottom. just cut the loop. but i think you have something else wrong. never heard of a cdi causing this over my 13 years but i guess there is a first time for everything. so let me get this straight. you think the rpm reduction is kicking in. is the buzzer coming on at this time or do you just not get the rpm's.

[n2yjc]

Slim, The buzzer does not sound when the revs are linited... Lou

[jb123]

how long have you had this motor and has it always done this?
is your oil injection hooked up or premix ?
has ANY rewiring been done on the motor or ALL factory connections?
what are the tank levels when this happens?

[slim]

it just seems to me that you have another problem and not really going into rpm reduction. if the tank level is fine and the buzzer is working, nothing is pointing to rpm reduction. have you checked the timing to see if it is advancing? how far have you went into checking this thing out? fuel and compression also. i just want to know what you have done so we can narrow it down.

[n2yjc]

JB, I have had this engine for 2 months, it came on a 17' whaler that I bought. This did not happen when I test drove the boat, but the seller may have run the engine earlier that day. Oil injection is hooked up and working fine. I fill the tank every other time I use the boat. All of the harness and wiring look original, it does not look like anyone has screwed around with it.

Slim, Timing advance is working fine, I have gone thru 10 or more (6 gal) tanks of fuel, Compression is 115 - 115 - 113. Remember this engine runs great once it has been runnung 10 or 15 minutes.

I am starting to think that the CDI unit has got a thermal problem or maybe moisture intrusion within the potting. Last resort will be to replace it and see if that fixes the problem.

Anyway, I have been away on a buisness trip for the last few days, but tomorow I am going to see if I have that "Grey loop of wire" that you mentioned on my CDI unit. If i am able to eliminat the rev limiter and have to rely on the buzzer in the event of low oil or over temp, so be it. Again, Thanks for all or your help on this... Lou

[slim]

well if you can, when you cut the gray loop, leave enough to reconnect incase this doesnt solve your problem. usually when a cdi breaks down from thermal, its goes out after it heats up. not the opposite. this is the way all the electrical parts are. coils and spark plugs also. all break down after they get hot.

[jb123]

about your oil, IF you have a clogged filter in the aux tank, it may take some time to fill the main, causing the issue, or if there is a bad check valve, letting it gravity feed back down.

[n2yjc]

Slim, I don’t have the grey wire loop - What I do have is an "over rev terminal with nothing hooked up to it.

JB, I don’t have a remote oil tank, just the tank under the engine cowl.

I think my next step is to remove the CDI unit and inspect it closely for cracks depending what I find, I think I am going to bake it at about 220 deg. then while its still warm spray the entire unit with electronic conformal coating. I still suspect the there may be moisture intrusion. If baking and sealing works, then I will just replace the CDI. - Lou