I Bad Need Some Yamaha Help..1996 40HP

[PanamaRanger]

1996 40HP TLRU.
I have had it workd on twice for this and no fix. Please help if you can.
In the morning when it is cold it will sort of miss for maybe 500 yards and then it is sort of like it starts hitting on all three cylinders or it feels like it is a car when it goes into passing gear a little. It is sort of like it has to warm up but it did not used to do that. If it sits just a minute or two and crank it, it runs fine. If I fish for maybe an hour then it does it again. Like it happens when it cools off. My Yamaha mechanic checked it all out and ran it on the water and he sees what I say but does not know what it is. He says it is not fuel related. I changed plugs and ran some tune up through it and no help. My mechanic said it was maybe the expensive computer board but said to go ahead and run it like it is. It acts like it has to warm up some and then runs smoothly.

I would like to fix it. One mechanic said it was the coil on one of the plugs but could not tell which cylinder and it was expensive to change all three. I was also told it was a CDI...but can't tell....I am needing some help with this. Anybody got any advice? Thanks...Panama.

 

[bodogg]

Re: I Bad Need Some Yamaha Help..1996 40HP

Hi, panama, Im sorry to say this but it sounds like the mechanic was not a real yamaha mechanic to hear the problem and tell you that you should still run it. A coil will either work or not if all engine grounds are free of corrosion. So check your wiring harness completly for corrosion or scrapes,check your fuel system from tank to cylinder for any blockage or gelling from this wonderful gas we buy these days. I strongly beleive you will find your problem with out going any further.

 

[JB]

Re: I Bad Need Some Yamaha Help..1996 40HP

Seems like a temperature related issue. Something doesn't work until it is warmed up. That could be any number of things, most likely electrical.

Fire her up on the muffs and use a hair dryer (NOT a heat gun) to warm what you can reach in the ignition system. If you can get it to smooth out by warming a particular part. . . .guess what?

 

[JoLin]

Re: I Bad Need Some Yamaha Help..1996 40HP

I'm really sorry to confuse matters, and I'm the first to admit that my mechanical expertise is all home grown. In my personal experience, however, a failing electrical component will tend to act up when it's warm rather than cold, due to increased relectrical resistance in the part as its temperature rises. I've experienced it in older cars with failing ignition coils, condensers and broken spark plug leads. They'd run okay cold, and cause misfire as they warmed up.

I'd be much more inclined to look at the fuel system. This sounds all the world to me like a faulty choke or similar.

My .02

 

[JB]

Re: I Bad Need Some Yamaha Help..1996 40HP

Electrical parts, especially semiconductor devices, may fail from heat or may require heat to work, John. A fractured semiconductor junction may be "sealed" when warmed up.

Resistance does not change with temperature, but physical dimension does. That may either break or temporarily fix a component.

 

[Capt Ken]

Re: I Bad Need Some Yamaha Help..1996 40HP

Gonna go for the stretch here. If this is Panama, Panama, then it's probably runs in salt water. I've seen salt get built up around coils and such and when the engine sits, the salt attracts moisture. This causes grounding until the engine warms enough to dry the salt out. Try giving the power head a bath with freshwater and spray soap. Then let it dry in the sun.

 

[99yam40]

Re: I Bad Need Some Yamaha Help..1996 40HP

Testing to see if you are loosing spark can easily be done with a timing light hooked to the different plug wires while problem is there or use a spark tester. If there is loss of spark the start testing ignition system like the service manual states.
If there is no loss of spark then you are having a fuel problem to chase.
A leaking fuel pump can cause #3 run too rich and may fire better once warmed up and enrichment system turns off, if this motor has that

 

[PanamaRanger]

Re: I Bad Need Some Yamaha Help..1996 40HP

You guys have given me some good things to think about and check. Thank you. I do not live in Panama At this time and I am serving elsewhere.....and the motor never sees salt water. The mechanic I have closeby is not a real Yamaha mechanic but a general marine motor mechanic. They work on everything. I live in a rural setting and it is a LONG way to where a certified Yamaha mechanic is. The gas alone to take the boat to the city and leave it and then pick it up a few days later would be expensive.
I will need to try to solve it on my own if I can. I do not think the guy here knows what to do with it. They are a good honest repair shop but this is going to take a REAL technician I think to figure it out. That is why I thought I would try here. Thanks. Any other suggestions, please let them come. I like the idea about a spark tester and going from there to fuel or electrical.

 

[99yam40]

Re: I Bad Need Some Yamaha Help..1996 40HP

That motor has the prime start enrichment system.
Are you in a cold climate?
It has a diaphragm , electrotermal valve, o rings, hoses, and passages that all need to be inspected and cleaned/repaired if needed.
If the motor has good compression, spark, and timing, you could try turning the red emergency lever to the off position or to the open position to see if that changes anything while problem is there

A Yamaha service manual for you motor will give lots of info, but here is something to read up on if you want to test the ignition system http://issuu.com/cdielectronics/docs/troubleshootingguide/124?mode=a_p
It is kind of long as it covers so many different makes and models , but there are some specs toward the end for Yamaha

 

[PanamaRanger]

Re: I Bad Need Some Yamaha Help..1996 40HP

No, not in a very cold climate at all. 80s during the day now and 50s or so at night. This is a real puzzling thing for me. I do not know about the red emergency lever. It is on a aluminum boat with a steering console and has a kill switch???? It is a 40 TLRU. I was working today and could not get something to check the spark. I am scared to mess with it while in the water as I am afraid I will drop something in the water and really be in a mess. I am going to pull it out in a week or so and have it on a trailer with the muffs available and it will be safer for me to work on it then. I hope I can use the knowledge here to have a plan of action in place when I pull it out and know step by step what I need to do to troubleshoot it and find the problem. I am taking notes and keeping all the suggestions. The are so many things that could be wrong that it is a little overwhelming to me. I just want to thank everybody for trying to help.

 

[PanamaRanger]

Re: I Bad Need Some Yamaha Help..1996 40HP

By the way, I do have a tach on it. When it is running right, with the prop it has it runs about 5300 RPM. When it is having the trouble when the motor is cold or when it starts after sitting for quite a while...when it has the problem it is missing like a plug is missing or it is choked....in this condition it runs about 4700 RPM. Then after 500 yards or so or maybe 30 seconds to one minute, it jumps all of a sudden to the 5300 and takes off just fine and runs fine till I shut it down. If I shut it down for just a short while, it starts and runs at 5300 .... If I fish for a couple of hours, it does the slow start thing again. I thought I might be redundant and try to explain better. Thanks to all.

 

[PanamaRanger]

Re: I Bad Need Some Yamaha Help..1996 40HP

Hi, panama, Im sorry to say this but it sounds like the mechanic was not a real yamaha mechanic to hear the problem and tell you that you should still run it. A coil will either work or not if all engine grounds are free of corrosion. So check your wiring harness completly for corrosion or scrapes,check your fuel system from tank to cylinder for any blockage or gelling from this wonderful gas we buy these days. I strongly beleive you will find your problem with out going any further.

I have a few stations around me that offer pure gas without ethanol and that is all that goes in this motor. I buy it and carry it down to the boat in plastic gas cans. It gets Seafoam regularly and only gets Yamaha 2 cycle oil. I did not see a problem with the wiring harness but did not disconnect stuff yet. It is sitting in the water now and I am afraid I will drop something in the water. I am going to pull the boat out in the next few days and work on it with muffs on the trailer. That would be safer for me. I have dropped things like screws, chisel, drill bits, or screwdriver and a phone in the water so I am gunshy about doing much there. I am trying to get a plan of attack together for when I take it out. thanks for all the suggestions.