2004 115 two stroke rough idle and dies

[jkloppe]

I have a 2004 two stroke 115TXRC that I cannot get to idle correctly and it bogs down when put into gear and dies. Ran great last year, stored for the winter with a half filled tank. It ran good the first time i had it out with a few coughs and a little rough start. Next time it was out same thing, rough start, fished for a while and took a long time to get it started back up. Ran good back to the dock. Next time it was out, rough start and then died while we were trolling out of the dock area, limped back to the ramp.

From here i changed all of the fuel lines and fuel/water separator. New fuel pump and took it to a mech who rebuilt carbs and tested the fuel for water (no water in fuel). He got it running on muff and it seemed to idle fine, took it to the water and idled horribly and did the same thing as before died when put into gear. took it back to mechanic and we are working on it together at this point.

Today we replaced the tstats (not in great shape), and spent 2 hours tying to get it to idle correctly. Tested spark, was weak on one cylinder and we cleaned the grounds and it was firing good. Adjusted the timing to spec and same thing. we got it to idle at specs but not when put into gear more times than not it would bog down and die during any type of acceleration (done in testing tank).

I am trying to figure out where to look from here. there was a leaking gasket in the poppet valve (not sure if spelled correctly and not sure how long it was leaking) this was fixed as well. I am leaning towards the computer (due to water being thrown around in the cowling) or the stator? I may have him do a link and sync with the carbs again (maybe it wasn't done correctly?)

Any advice would be great! you guys have helped me with many problems on several boats in the past.

Justin.

 

[rejesterd]

Hey Justin.

Definitely sounds like a lack of fuel being delivered.

Are you sure the fuel tank is venting? If you open the gas cap, do you hear any hissing/pressure relief?

If not, I would check the fuel pump next. That's a critical thing because if the diaphragm inside has a hole in it, that means fuel may have leaked into the crankcase (it's powered mechanically by the crank shaft). If you find that it does have a hole, I would do a compression test on all cylinders to make sure low compression isn't your problem.

Other than that, I think fuel line joints are the only thing you didn't mention. Those can get clogged and the issue would reveal itself when you try to accelerate.

 

[jkloppe]

Thank you for the response. I will double check that the tank is venting.
I did a compression test and got 115 on all 4 cylinders. Next thing i will do is pull the lines for the joints and clean/check them out.

 

[rejesterd]

115 across the board should be good.

It's interesting that the mechanic rebuilt the carbs and it ran fine on the muffs, but then as soon as you took it out on the water, it was not idling fine. Have you replace all the plugs? Worth a shot.

Also, the idle speed needs to be adjusted after the engine warms up. So maybe the screws need further adjusting.

 

[jkloppe]

Thank you for the responses. Mech took another look at compression after everything else checked out. Compression got to 120 on all then would drop and not hold the compression on all four cylinders. Also failed a leak down rest, he says that it’s leaking across the engine. Head gaskets we’re in bad shape. New ones coming in tomorrow so hopefully that will solve the issue and not the rings. Keeping fingers crossed.

 

[jkloppe]

update.

compression has been fixed, new head gaskets, holds compression at 124 on all 4 cylinders. still not performing correctly. We found a leak on a gasket behind the carbs and that was replaced we thought this was the problem and it would fix it. Adjusted everything back to factory settings and redid the timing. Took it to the water and it ran great. Idled pretty good and was not bogging down so we thought all was well.

Took it to the water yesterday, started up great, got on plane no bogging down. Took it a few miles down the inter-coastal and at the turn around the bulb was sucked dry and it sputtered and died. I opened the gas cap and air came screaming in. from this point the problems seemed to start again, it took a long time to get it started again and to the point that i could put it into gear. Got it in gear and didnt stop until we got to the marina. Coming into the marina and going into neutral to coast into the dock it died again and i couldn't get it started. got it out finally and did some more testing.

replaced bulb with a better one and blew out the tank vent. It turns out i had my gas cap way to tight and the o ring was blocking the vent passages. So i took it back to the water and played with the idle adjust thinking that it may have backed out on the run the day prior. I could not get it back to where it would idle good and not bog down in gear. I have loaded some videos and added links to them. Please let me know what you guys think i could check next? here is a list of what has been done.

t-stats
head gaskets
plugs (gapped at .44)
pulled flywheel and cleaned optical sensors (mech)
fuel pump.
new fuel lines from tank to engine (except the lines from the fuel pump to the engine)
replaced gear oil (dirty but not bad)
new fuel water separator
fuel was checked for water (no water)
compression 124 all around
timing adjusted

https://youtu.be/t4A6qntJtN4 there is a knocking noise twice in this one (not sure how serious or what it is
https://youtu.be/MULIAjzw06E
https://youtu.be/Cs9S3JajqMA neutral and in gear
https://youtu.be/haVn0MQWiCM

please let me know what you guys think! thank you!

 

[robert graham]

Remove each idle mixture screws(remember turns out from lightly seated), spray out orifice with carb cleaner and compressed air, replace screws.....these tiny circuits can get plugged with debris and cause rough idle, etc. this method worked great on my 1999 C90 Yamaha....easy to do...

 

[jkloppe]

Thank you Robert, I will try that tomorrow.

 

[jkloppe]

Fixed!!! The idle mixture screws had welch caps on them so he did not touch them during the rebuilds. I removed the welch caps, counted the turns in (1.5) and adjusted from there. Ended up needing an extra 3/4 turn out on each screw. Runs great! thank you everyone for the help.