70TLRT 4 Maintance Repairs & Still Malfunctioning

[tafishing]

Hello all,

First time user at Yamaha Outboard Parts and hope that I can get some help as well as document this issue for others to use. Let me give some background on what has been happening and the steps I have tried to correct it.

My 1995 70 TLRT two stroke engine has continually had problems getting on plane (stalling during throttle up). This started about 6 months ago and has gotten to the point were I believe damage can be done to the boat trying to drive it anymore. The engine starts just fine and then seems to either misfire or drop a cylinder. I am not positive but I see a lot of shaking and hear on and off sound differences. Before the problem had progressed into every acceleration I could jump on the throttle and get out of the hole. Once I get on plane the top end seems to be fine, but if I accelerate slowly the low to mid RPMs bog down.

Troubleshooting my way through this has been nothing but headaches and a long season of missed fishing opportunities. First I rebuilt the carbs thinking maybe a clogged jet was to blame. Next the fuel line going to the portable gas tank was replaced for the possibility of ethanol corrosion. Once that did not fix the problem I bought a compression test kit and verified pressure on all cylinders (115-120). This weekend I replaced the fuel pump and all the inner fuel lines.

With all of these repairs done and still problem existing I am at the point of pure frustration. Looking over the manual I believe to have narrowed the problem down to 3 different components: Ignition Coils, Pulser coil, or the CDI.

Not wanting to buy all three of these (5 if you count each ignition coil) I was hoping to have some help to try and better diagnose these parts. Can anyone tell me of a good way to verify these components? My sanity is in your hands. Thank you very much for any help/tips in advance.


Regards,
TAfishing

[ausnoelm]

Are you 100% sure the carbs were done properly? spray cleaners and a wash out will not clean them, they need to be removed, dismantled, cleaned and rebuilt, Yamaha have very small orifices that require very carefull cleaning, do you have a genuine manual?

[99yam40]

Yes there are tests for those parts in service manual.
Do you have a peak reading volt meter made for these ignition systems?
If not pick one up or a DVA adapter with a regular meter will work, there are ohm readings you can check also.

A inductive timing light and/or spark tester can indicate a spark failure when hooked to plug wires, but you will need the proper test equipment to do proper testing.

See if page 97 will help Specs maybe around page 100
CDI Electronics Practical Outboard Ignition Troubleshooting

[tafishing]

ausoelm- Yes I broke down all 3 carbs and did a full service on them. Is there any way to say this was done correctly from some sort of test? I can tell that fuel is getting to all three plugs as I replaced them and checked for gas.

99yam40- I have done most of the resistance checks and all are on but the the three parts listed. An odd thing found was the book is asking for an OHM reading of 4.88k for pulser, but most other online records are around 300 ohms(which is what I measured) I have a DMM, but I am not sure what a DVA tester is can you please elaborate? I will provide stats on what I have OHM tested and what the book asks for tinight. Also the CDI test booklet looks like a good place for me to move forward.

Thanks for the quick replys!

[tafishing]

Also I do have the Genuine Yamaha Book

[99yam40]

Look at page 3 of that link I sent about DVA

[johnkopp]

On my 90 years ago the CDI was going out. Hard for mechanic to trouble shoot. Once we went out on the lake first thing in am, it would not do it. We guessed that was it after he had thrown coils and some other stuff at it. I now know why it worked for him. He had the cowling off the motor and it was a cooler CDI operating under that condition.

It was the heat from the motor breaking it down. A slow speed up out of the hole makes this part get hotter than a quick one. The part is mounted right next to the motor and is all sealed with black epoxy and I think that is the CDI. Anyway it was bad only when the motor applied enough heat to it. Back off on throdle and it would start to work again. Try and pull up a skier and it did its thing. My motor is a 1985 and I think this happened around 1995. I still have some good spare parts from trying to fix this.

Try running your motor with cowling off to see if it works better then you know.
John

[tafishing]

I have purchased a DVA online and will be trying out these tests soon. My wife has kept me from working on the boat until the holiday, but I will give more information when available.

Also I have not ran the boat out of the hole with the cowling off, but the problem has progressed to issues even when testing in the driveway. With that said after it sits and I try it out again for the first 10-15 seconds it sounds like it runs smooth (Just to throw more confusion and info out...)

TAfishing

[tafishing]

The motor will not start in the driveway anymore. I have taken measurements with a DMM for resistance. I have attached the pages that apply to my electrical system. Hope that this can create a better picture for some of you more experienced people.

If anyone knows how to make this pdf viewable without download please tell me and I will change it. I am all for questions if you have any.

TAfishing

[tafishing]

70TLRT 4 Maintance Repairs & Still Malfunctioning (Updated Measurements!)

Updated title for those following.

[99yam40]

Post the peak voltage readings you get with DVA adapter

[tafishing]

I meant to tell you this before, but the cart for the CDI Yamaha does not match up to my motor. I still will take measurements.

[99yam40]

the cart for the CDI Yamaha does not match up to my motor

Not sure what you mean by this

[99yam40]

An odd thing found was the book is asking for an OHM reading of 4.88k for pulser, but most other online records are around 300 ohms

If you look at your manual the part that is printed for the pulser is a miss print.
Notice the box says secondary coil resistance?
Look at the specification page to find the proper spec, it should be like all the rest of the places you have seen it (about 300 ohms should be fine )

Not sure why you have 10K and 4.4K listed for the secondary coil resistance

Peak voltage is the best test for CDI inputs and outputs, but according to your reading you posted there seems be be a problem.

But you said you are using a DMM and the manual says not to use a digital meter, only use analogue meter for testing CDI

[tafishing]

Not sure why you have 10K and 4.4K listed for the secondary coil resistance

This brings up a point I was going to ask. With the spark plug boot on my measurements are the first 9-11K reading. After unscrewing the coil boots my readings went to the 4.3-4.5K. Does this mean my boots are corroded?