1989 225 Yamaha excel Runs great Except at WOT

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

So the motor ran smooth without firing on all 6?

How did you make out?

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

It is a weak spark on Number 2.

So weak it is fouling the plug totally out...........(I did get offshore on Saturday enven though the boat ran like crap.)

The alternate used CDI sounded better actually ran worse!!!!!!!!!!!
(I was sure that was my issue)

Back to the beginning:
Pulsar Coil to CDI to Microcomputer. This time I am going to check all wires associated. (With all that I have done I am trying to rule out shorts) I did get a Selock Manual that seem to have more information including the voltages for the pulsar coil and CDI.

How is yours running?

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Man thats too bad, I was really hoping that was it. Mine runs fine it just doesnt go over 4200 ish RPMS- I am willing to bet on that stator, thats the best thing I can come up with. All my plugs are clean and do not foul, they have 70 hours on them so far this season. Man I hope you get this figured out without dropping a ton of money. I am kind of waiting till next year to be honest, I only run at 3400 rpms at cruise so it doesnt worry me to much.

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Mine will not get out of its onw way. Very slow out of the hole. It is not missing just no power and its top RPM is 4100. If yours is getting on a plane fast you may have a prop issue.

After a day of boating I am still getting #2 fouled out completely............

But #2 is defintely firing. You can pull the plug wire off and see the spark and feel the engine miss..

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Well I bet we are chasing the same issue, loaded up the boat with 4 adults, 2 huge coolers, tents, chairs, firewood, the works- even a black lab and my boat did a top end of 12 mph with missing and so forth here and there. With the weight out of it, 4200 ish max rpms and no missing.

I am going to pull the carbs tonight, and adjust the timing to see where I stand. I almost wonder if it is fuel starvation, but I still suspect that high speed stator is screwy.

I will post my results.

 

[joehac]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Wow, you people have the same problem I have. I have tried everything for about a month & have come up empty. I have also moved into the electronics after replacing everything along the fuel path (including the carb). I am starting to settle in on the CDI &/or stator. Too expensive to guess. I have started trouble shooting them with the Clymer manual resistance checks. I will keep you guys posted.

1993 Yamaha 50hp engine on a 14' Boston Whaler. Runs great until about 3/4 throttle. Then there is nothing left. Getting about 25 mph & it used to get 35 mph.

I have torn apart, cleaned, & replaced everything along the fuel path. I removed the exhaust & looked for any obstructions. I thought there was an inkling of a weak spark & replaced the coil & plug wire assembly. Pressure check gives me between 150 & 155 PSI. Nothing has made a difference. There are some signs that I am running rich in general.

Now I am trying to trouble shoot the CDI & the stator but am not that good with electronics - but they are sooo expensive that I need to figure it out instead of just replacing!

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

My understanding has always been that when a CDI is bad, its bad and you know it by either it not running or barley running. Now this stator- since it has a high and low circuit, a bad stator could in theory run fine until the high speed stator circuit needs to kick in- which never happens. Hence the 3/4 throttle to full throttle generating nothing- it is running great off the low speed side and cant get a "shift" to the high speed circuit.

That is my understanding anyhow.

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Hey guys, I need to break down and actually test my stator with a multimeter- I will let ya know what I find. I am an electrician so it figures im the last one to do the electrical test!

 

[joehac]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Some one please tell me more about the "high speed stator coil". I guess I don't understand the stator assembly. Lighting coil? Pulse coil? charge coil? I thought there were only 3?

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

My engine is not running on all 6 cylinders I now know that much, on side of the block feels much hotter than the other- its cool to the touch, pulling plugs doesnt make much diff either. Occasionally it will fire all 6 and the idle will run to 2000 rpms- smoke like the water is on fire, then die back down to 800 rpms or so. I am going to replace all the plugs tommorow, one had carbon buildup, #3 I think. This engine is going downhill FAST. It is in a slip and I tinker with it a lot.

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

I got some really off numbers when I tested the CDI's resistance, really really off. They were much higher then the manual states they should be. I also read in the manual that without a yamaha pocket tester you will not read accurate values when testing?

About ready to buy a CDI.

The stator values are the same as Muellers so I have thrown that out the window.

Yamaha Gurus- HELP!

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Also, my tach shuts off at will, comes and goes- this must be a clue in terms of where the signal is generated, right?

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

How are you making out Mueller?

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

I at least have a consistent problem:

LAst week changed out CDI's:
Yesterday Changed out the Computer:

I should have realized that your's was a sign.
This next couple of days I will do the stator and pulsar coils........................
I am lucky to have the access to the parts.........only have $120 invested in all of the experiments..................and lots of time..........sure glad I am unemployed right now!

The only thing left are the stato and pulsar coils and the wiring harness.

I did run it as one of the Tech's instructed, on the trailer and was able to hear it missing under load,,,,,,interesting that it dose not seem to miss in the water.........still slow to get to a plane........

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Well I ordered the computer/cdi (mine are all one unit) still dont have it yet. Did you run it with the new computer in it yet or not? I assume that didnt fix your problem?

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Yes, used computer still had the problem..............At least it did not give me a new problem........

I finally brought the boat into the man.................

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

So whats the man say the problem is? Mine were dirty carbs (even though they looked clean?) so there must have been a hidden blockage. The boat runs like heck now, 40 mph- which is fast in this boat!

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

You get any word yet Mueller?

 

[Johnshan1]

Re: 1989 225 Yamaha excel Runs great Except at WOT

Come on man! Whats the good word?

 

[Mueller1956]

Re: 1989 225 Yamaha excel Runs great Except at WOT

@What a trip this has been. Brought it to one the areas better shops and now they are stumped. Everything from Reeds to coils and back again to carbs.................

Number 2 plug will still foul out after a 2 hour run.............I am going to get it this week and try something else............I am afraid that I have wiring issues that are causing us to not find the issue.............

More to come

Sorry been gone and now started a new job........no more just pondering the engine............

Mueller