Yamaha 9.9hp I AM TROWING THE TOWEL!!!!!

[puleasca]

Hello
I have a Yamaha F9.9 MSHS 4 stroke 1994. The main problem is no power under load. Starts fine, idles fine and accelerates fine on the muffs. Under load is a different story: it doesn’t go over 2000rpm and no power. The boat is 14f jon boat and it worked fine before.
Now this is what I did so far: new fuel line, new bulb, new gas tank, new gas.
New carburetor kit. New water propeler and all the rings in the lower unit. New valves .new head gasket, new exhaust gaskets, new fuel pump membrane and new thermostat. I checked all the electrical parts and all are in specs. Last year I bought a new CDI.


I AM TROWING THE TOWEL!!!!! PLEASE HELP!!!!

[99yam40]

does it have good compression, good strong spark on all plugs even when the problem shows up?

, does the timing advance as it should (meet idle and WOT specs),
and does it stay in spec when the problem shows up?

[puleasca]

Thank you for replying. Good compression on both cylinder #1- 130, #2 -135 cold engine. Spark jumps 7/16 on both. and it is blueish in color. I started it in the dark and no sparks in other places.

[puleasca]

Update!!!

I was trying to clean some connection between the CDI and the oil pressure wires and I applied a little pressure on the CDI, with the engine running, and started to sound a little better. I kept the pressure on the plastic of the CDI, accelerate and the engine run like a champ .When I take the pressure out comes back to the old self. What is this? The CDI is almost new!Can that be the cause?

[99yam40]

it is a possibility,
but what is the motor doing?

loosing spark to one or more plugs randomly or just one all the time?

changing timing?
too far retarded or advanced

[puleasca]

This is what I did. I put a small wood clamp over the CDI and ran it like that in my pond. It is like dream! Never ran like that since I have this boat.

[99yam40]

You still have not said what it is doing.
CDI controls spark and timing.
something is changing
what is changing?

[99yam40]

Hello
The boat is 14f jon boat and it worked fine before.

you said it worked fine before , so how can you now say it runs better than it ever did. Dose not make any sense to me

[puleasca]

Sorry for the confusion. I thought it run fine before until I run it today. I can see the difference. And to answer your question : the timing is ok. The flywheel mark is inside WOT mark around 4700 rpm .

[puleasca]

Why does it work when I press the CDI? What is inside the CDI that can change by pressing ? What are the bad CDI symptoms?

[99yam40]

Sorry for the confusion. I thought it run fine before until I run it today. I can see the difference. And to answer your question : the timing is ok. The flywheel mark is inside WOT mark around 4700 rpm .

unless you test/check with a timing light how can you say it is where it should be
apparently you have no idea what the timing is doing

[exeter27]

Here's a guess. Pushing on the CDI unit is improving a poor electrical (maybe ground) connection somewhere. I'd suggest cleaning all your electrical connections.

[puleasca]

ok. I will check all the electrical connections and the ground and I will be back with the results.