1999 Yamaha 50 2 stroke ej

[Monarchyam50]

Hoping to get some help on a motor I have purchased roughly a year ago. I have a 1999 Yamaha 50 2 stroke motor that has needed a little fine tuning to get going. The long and short is I have rebuilt the carbs, cleaned and blown out, rebuilt the lower unit, and removed the oil injection system.

I have had some poor idling issues which led me
down the carb rebuild. Needless to say it didn’t necessarily solve all the problems. It cleared up some of the issues but the main one I am
having is this:

i purchased the manual to try to get everything back to spec. All linkages have been set to factory. When setting the CDI linkage, it calls for 7 degree. The issue is it runs terrible at the timing mark on the side of the CDI. So I got out the timing light to check to see where it was hitting and it’s not even on the map. I did a TDAC test and the flywheel is correct for TDAC. But the CDI and flywheel are not matched up. Meaning 7 degree in the CDI is more like 14 or 15 on the flywheel.

if I adjust the stop screw all the way out, it brings the timing on the flywheel to about 10. The boat idles really well there.

is there any reason the marks aren’t in sun with each other? seems like advancing the timing in the CDI that far would hurt the timing curve.

[99yam40]

I had the same problem with my C40TLRX, If I remember correctly the WOT time gets out of wack by screwing with the Idle timing that far
A new CDI fixed it

[Monarchyam50]

I’m hoping there is an alternative solution. The amount of time and money I have in this motor is beyond rationalizing a $600 CDI

so when we got the motor I found quite a few things moved, which told me that the motor had been messed with. Carbs were about 4 turns out, fuel filter was loose, etc.

is it possible that the pointer has been take off the CDI and turned to be out of sync?

I checked WOT and it is at 24

thanks for the quick reply

[99yam40]

if it is OK when pointed at the mark for 25, and is not when pointed at 7 then something has to be wrong inside.

have you looked for after market ones?
try looking up CDI electronics
I think this part would fit yours
117-63D-04

[Monarchyam50]

I agree something is wrong. I’ve chased a problem with fuel for a month that now has turned out to be timing. My wishful thinking has me creating a scenario that all I have to do is adjust this one thing and it will work.

I saw the ones on eBay for 125 bucks. Seems like a decent scenario and a would be happy to pull the trigger.

is there a test to run on the CDI? That doesn’t require Yamaha special tools?

[99yam40]

as far as I know no testing for the CDI timing parts, just set to marks and then fine tune with a light

yea, I know what you mean.
when I picked up this C40 back in 08 , I went thru the carbs many times trying to get this to run properly.
even after replacing the CDI to correct the timing problem I had a hi speed miss that took me over a year to figure out someone had drilled out the main jets.
replaced them and all was well until the crank main bearing started wining.
pulled the crank and sent it off for rebuild.
put that back in and replaced the crankcase recirculation check valves and the motor runs better than ever.
but salt water is taking its toll on the power head cooling passages, eating into the block

[Monarchyam50]

I have access to a 70 Yamaha parts motor. From what I can tell 50/60/70 CDI are interchangeable. I’m going to take the one off of the 70 and install temporarily to see if that gets me to where I need to be. If it does I’ll order a new.

the good news is the motor is mechanically strong. Spark plugs look good. Fixed all the fuel leaks ( there were a ton). Compression is good. Lower unit completely rebuilt( bad seals which froze the bearings and rusted all the gears). At this point I have done almost everything to it to make it a strong motor which is why I hate to give up so close to the finish line. But dang I hate dropping another $600. Lol

I guess that’s why they say the best boat is your best friends boat.

[99yam40]

in that year range the 40 and 50 are interchangeable, not 60 and 70
if you can find one on e bay for cheap that may be an option
or as I posted buy an aftermarket

I hope you knew what you were doing when removing the oil system

[boscoe99]

in that year range the 40 and 50 are interchangeable, not 60 and 70
if you can find one on e bay for cheap that may be an option
or as I posted buy an aftermarket

I hope you knew what you were doing when removing the oil system

If the oil system was removed then he did not know what he was doing.

I am beginning to feel more and more like rodnut.

[Monarchyam50]

Boscoe99- how do you come to that conclusion?

oil system removal was pretty easy. Not sure what you mean by if he removed it “he didn’t know what he was doing”. Please elaborate on how it could be harder than building a block off plate- Removing the gear-sealing the inlets on the back side of the carbs.

99yam- thanks for the heads up. I did just read that only the 40 and 50 were interchangeable. Which I should have known since my mech book only shows 40 and 50.

[boscoe99]

Boscoe99- how do you come to that conclusion?

oil system removal was pretty easy. Not sure what you mean by if he removed it “he didn’t know what he was doing”. Please elaborate on how it could be harder than building a block off plate- Removing the gear-sealing the inlets on the back side of the carbs.

99yam- thanks for the heads up. I did just read that only the 40 and 50 were interchangeable. Which I should have known since my mech book only shows 40 and 50.

Not saying that technically you did not know how to remove the oil system. Saying that you did not know what you were doing by deciding to remove the system in the first. place. Faulty judgement.

[99yam40]

gear driven pump systems off of the crankshaft is not something that fails because of mechanical failures.
crank turns, the pump turns
now if you let water/ sludge collect in the oil tank that can be a problem.
do the normal maintenance and they are good to go.

but as you know running a 50hp motor on premix is a lot different than running a 250.
lot less oil and gas has to be mixed.
my 6 gallon tank can last for 3 trips maybe the way I fish and where, but I usually fill up before each trip, just in case I want to head somewhere out of the ordinary or pull someone back out of the bay.
done that 2 times only in the last 10 years

[Monarchyam50]

Boaco99- I believe my judgement is justified. I don’t want the opportunity for someone to forget to add oil and run it dry. There really was no need for your comment since it’s opinionated. I was asking facts referring to the CDI and giving insight to what was done to the motor. But if your little 2 cents to be an internet king makes you sleep at night then by all means stroke your ego.

99yam yea I was torn between leaving it or removing it. Went with removing it for a few different reasons. One being it’s something else to have to check when doing a once over. 2 being just a piece of mind to know I mixed it. At best I’m mixing 15 gallons. This is a duck boat so it takes some abuse. 3 being that I can adjust my own mix to lean it out a little if needed through the ban. Thanks for your help.

[99yam40]

there is a warning system when the oil tank gets low, and I have known people to forget to add oil even to premix motors.
It is what it is now, so make sure it is mixed properly

make it a habit to only put the oil in right when adding gas.
it can be a pain trying to figure out how much oil to put in if you do not know how much gas you are going to put in

[Monarchyam50]

Yea to me it’s just easier to premix. I ran the Oiler for a little while and just didn’t like the process. I’ve had boats for almost my whole life so mixing is like second nature. Aside from my Mariah Shabah z with a 350 I/o, I’ve only had 2 stroke motors.

again, I appreciate the help.