Yamaha F60TLRB 2003 4 stoke - running wonky

[ksdhillon]

I recently bought a jon boat for duck hunting that came with an “as-is” 2003 60 HP 4 stroke F60TLRB engine. The engine was hard to start and once it gets running and warms up it would run fine at idle. Any attempt to increase throttle would result in coughing, choking and the engine would stall.

This site has been an excellent resource for someone like me just starting out. I changed the fuel tank, fuel lines and primer bulb. Also changed the water separator and the fuel filter mounted to the engine. There was a lot of water in the separator. I changed the spark plugs as well. The old spark plugs actually looked really good. Oil is clean and had been recently changed.

Once I did all of that, it starts a little easier and I can rev up in neutral with no problem. Once its put in gear though when I increase the throttle it still coughs, chokes and stalls if I add throttle too fast. If I add throttle very slowly and let the engine RPMs catch up, I can eventually get it to increase to WOT.

My process has been to replace the easiest/cheapest things that may be causing the problem but so far it hasn’t solved my issue. I just ordered a service manual that I should get in a week or so. My question is – is it worth the effort to remove and inspect the diaphragm in the prime starter assembly or should I just move forward with removing and cleaning the 4 carbs? Although I am well experienced with small engine repair, the 4 carb stack looks a little intimidating. I don’t have access to an ultrasonic cleaner to clean the carb parts, which seems to be what many folks recommend. I would likely take it do a mechanic which I would expect will set me back several hundred $$.

Any thoughts on other things to try before I undertake the carburetor removal would be appreciated. Thanks in advance.

 

[Faztbullet]

Carb sync and link most important on 4S as is idle mixture. If engine has been setting a long period it may have ethanol damage in carbs

 

[ksdhillon]

Fazbullet - Thank you for your quick reply. Once I get the service manual I will give those a try. much appreciated!

 

[racerone]

I think it will cost more than --" several hundred $$$ " ----If you resort to a shop.----Do 1 carburetor at a time.

 

[ksdhillon]

you are probably right on the $$. I watched some videos on taking them apart and it doesn't look real bad. Right now I am looking to get it running well enough to get me through duck season, then will try rebuilding the carbs. good idea 1 at a time... Thanks!

 

[99yam40]

I would try some Yamaha Ringfree Plus fuel additive in a cleaning dose.
2 oz to a gallon of gas.
drain all the lines, filters, & carb float bowls.
and then pump the new mix into them
open the drains on carb bowl and flush some thru, catching what you can and see if any water comes out.
crank it up and run for a while to make sure the ring free gets everywhere and then let it sit overnight.
crank it up again and see if it gets better.
may need to repeat several times if it is just gummed up jets and passages.

good luck

 

[ksdhillon]

Great suggestion as well. thanks a lot. I will try and do this next weekend.

 

[ksdhillon]

So today I treated a gallon of gas with 2 oz of Ringfree Plus for a cleaning dose. I emptied the carbs and the water seperator and the filter. Then pumped the treated gas all the way through and let it run for 15 minutes. While it was running I decided to try removing the spark plug wires, one at a time. I read that on another thread as something to try. I removed #1 and it was obvious, the engine almost stalled. #'s 2 and 3 though seemed to have no effect when removed. When #4 was removed the engine almost stalled. I didn't have time to remove the spark plugs from #2 and #3 to check for sparks. That's tomorrow's project. Still waiting on the service manual to do a disassembly of the carbs. I watched a video on synching the carbs, hoping to find a freind who has the rig to measure them.

 

[99yam40]

let it sit overnight and fire it up again tomorrow to see if it clears anything up.
let it run sometime again and then let it sit overnight again.
then one more time Sunday,
if no help carbs will need to come off and be cleaned

 

[racerone]

As they say.-----" most carburetor trouble turns out to be something else "----I would concentrate on spark issues first.----Likely nothing wrong on fuel side of things.

 

[ksdhillon]

Definitely going to let it sit overnight then try it tomorrow and then again Sunday. Also going to pull the #2 & #3 plugs and look for a spark. They both appear to be fed from the same coil.

 

[ksdhillon]

I ran it again today for 15 mins and it ran a lot better, revved up nicely although just in neutral with water muffs on. Before putting in the ringfree the engine would stall at the lowest idle, now it idles well - short video clip below. Going to let it sit overnight again and will run it tomorrow. Pulled the plugs and it looks like they are all sparking ok. I hope to get it out on the water soon, will report back on how it runs on open water. Thanks all for you help.