Hard Cold Start

[Soundear]

I have a 1998 Yamaha C115. I did a complete overhaul on the motor by changing the water pump assembly with upper and lower seals. The Motor was bogging down after I reached 2000RPM. I flushed the Gas tank, changed all hoses in boat as well as within the motor. I put a new fuel pump on it and bought 2 Carburetor kits and rebuilt both carbs. The motor started right up within 2 revolutions of the flywheel and currently runs perfect. The problem as of recent is that the motor will not start when cold unless I spray a little starting fluid in the carb intake at which point It starts right up! I used Seafoam in my tank and Gumout cleaner in the intake as my son drove the boat at different RPMs in hopes of cleaning what I suspect is a gas feed problem. I’m an audio engineer - not a marine engine mechanic - but I do enjoy working on my motor when I’m able to. Once the motor is warm, it starts on a dime. Does anybody have a suggestion as to why the motor is hard to start when cold?

[TownsendsFJR1300]

Can you confirm that the choke butterflys are closing fully?


https://www.boats.net/catalog/yamaha...lrw/carburetor

The choke knob, part #24: https://www.boats.net/catalog/yamaha...115tlrw/intake when pulled towards the operator, should close them fully.

[99yam40]

you cannot do a complete overhaul on a motor by replacing a few parts

spraying something into the carb while running does nothing to clean any part of the fuel system

[rejesterd]

Hello.

When the engine is cold, it needs a richer fuel/air mixture to stay running until it warms up. In later models, Yamaha added the Prime Start system (and eventually a computer-con*****ed idle control valve), but I think yours just has a choke. If you rebuilt both carbs and the screws are adjusted properly, then I don't think you have a fuel feed problem.. I would say it's just too much air intake when cold, and the choke is the solution for that.

If you find that your choke is busted, then just keep using the starting fluid.. nothing really wrong with that.

[99yam40]

starting fluid used on a 2 stroke is never good.
no lube in it

[boscoe99]

This place is getting more like THT every day. Sad.

[pstephens46]

Hello.

When the engine is cold, it needs a richer fuel/air mixture to stay running until it warms up. In later models, Yamaha added the Prime Start system (and eventually a computer-con*****ed idle control valve), but I think yours just has a choke. If you rebuilt both carbs and the screws are adjusted properly, then I don't think you have a fuel feed problem.. I would say it's just too much air intake when cold, and the choke is the solution for that.

If you find that your choke is busted, then just keep using the starting fluid.. nothing really wrong with that.

Boscoe is too nice. Me? Not so much.

Pipe down junior! Your advice sucks. Whatever you think you know is not helpful. Your advice sucks on THT too, btw.

OP, please ignore this advice.

[pstephens46]

Can you confirm that the choke butterflys are closing fully?


https://www.boats.net/catalog/yamaha...lrw/carburetor

The choke knob, part #24: https://www.boats.net/catalog/yamaha...115tlrw/intake when pulled towards the operator, should close them fully.

Soundear start here please.

[TownsendsFJR1300]

rejesterd apparently won't click on any links (or apparently read other posts) that shows THIS engine does NOT have Prime Start...



*rejesterd, for a FOUR STROKE engine, starting fluid if ok, for a TWO STROKE, it needs OIL.

PRE-MIX (oil and gas) in a "spritzer bottle" will work W/O damaging the engine..

[panasonic]

Hello.

When the engine is cold, it needs a richer fuel/air mixture to stay running until it warms up. In later models, Yamaha added the Prime Start system (and eventually a computer-con*****ed idle control valve), but I think yours just has a choke. If you rebuilt both carbs and the screws are adjusted properly, then I don't think you have a fuel feed problem.. I would say it's just too much air intake when cold, and the choke is the solution for that.

If you find that your choke is busted, then just keep using the starting fluid.. nothing really wrong with that.

The man came on here to look for help to FIX his engine...not being told that is OK to be blowing starting fluid down the carbs as a fix.
Anybody can post on here, and we are not always right, but most advice given here by the regulars is very solid.
Far as I can see you are quick to type and not think before hitting the post button.

Are you listening rejesterd?

Sorry Soundear we have a little problem here lately, please ignore the advice given from rejesterd. Check your choke plates as already mentioned in post #2.

[rodbolt17]

it is an electric choke with a manual backup.
does the electrical part work?
does it work when the starter is engaged?
yep, I have seen a few smoked pistons due to starter fluid.
only done this for about 30 years.

[Soundear]

Thanks everyone for the valued suggestions: I've received some great advice in the past from this forum and value all of the suggestions - Interesting about the spray start fluid not having oil...... makes sense..never realized that the motor can get damaged as a result!
The motor does have an electric choke as well as a "manual" pull Lever at the front of the motor on the lower left side cowl. I verified the electric choke as working via the Key switch (Yamaha remote push, hold & turn and I hear the chokes flap) and tried the manual override as well. I might take the front cover off the carbs to visibly verify the chokes are in fact closing and I'm not being tricked by the electric solenoid noise or the manual pull rod resistance.
I did observe something of interest on Sunday: I usually raise my motor for the week with my trim & tilt as to keep the motor out of the water until the following weekend. Last week I mistakingly left it in, went to start it and it started cold within 2 seconds (or just a few revolutions) Is it possible that the carbs are draining somehow when tilted and are not getting the gas at first when I lower the motor to start it?

[TownsendsFJR1300]

Thanks everyone for the valued suggestions: I've received some great advice in the past from this forum and value all of the suggestions - Interesting about the spray start fluid not having oil...... makes sense..never realized that the motor can get damaged as a result!
The motor does have an electric choke as well as a "manual" pull Lever at the front of the motor on the lower left side cowl. I verified the electric choke as working via the Key switch (Yamaha remote push, hold & turn and I hear the chokes flap) and tried the manual override as well. I might take the front cover off the carbs to visibly verify the chokes are in fact closing and I'm not being tricked by the electric solenoid noise or the manual pull rod resistance.
I did observe something of interest on Sunday: I usually raise my motor for the week with my trim & tilt as to keep the motor out of the water until the following weekend. Last week I mistakingly left it in, went to start it and it started cold within 2 seconds (or just a few revolutions) Is it possible that the carbs are draining somehow when tilted and are not getting the gas at first when I lower the motor to start it?

Visibly verify the choke is indeed closing. The solenoid may be working (making noise when activated), but disconnected..

Do you prime the primer bulb after it sits with the engine tilted (especially over time)?

[99yam40]

it is always best to put down and then pump the primer bulb to make sure all of the carb bowls are full of fuel before trying to start the motor, especially after a week of sitting

[Soundear]

I have a new problem: I took the advice of one of the expert mechanics on this forum and did not use Ether on my 2 cycle but instead mixed a little bit of oil in gas to prime the motor for starting. That seem to do the trick - it’s still not right but at least it’s safer. Then after a day out on the water on my way back I slowed the boat down then went to accelerate again and it seemed as if the motor was cavitating as if I hit a pocket of seaweed or possibly a bag I slowed the boat down to raise the motor to find nothing on the propeller. I put the motor back down to accelerate and still experienced the cavitation or revving within its own place almost as if I spun the prop hub.l I idled back to the dock, raised the motor and took off the prop. I saw no evidence of Of a damaged or separated hub so I check the spindle for any type of fishing line or other debris. I went back out for a ride to only experience the same thing. I decided to rebuild both carburetors with a Sierra kit. I suspected just maybe the floats were sticky or needed some adjustments. The kit did not come with replacement jets, but had all o rings and gaskets to rebuild them. After close inspection all looked good. I changed all gas filters on the motor, in-line and installed an OEM Water/Gas separator. I still have my problem with my engine bogging down upon acceleration to plane the boat. Any ideas?