Yamaha 50 new power loss

[Sperkinsrn]

I just bought a skiff with 2005 50hp 2 stroke trl Yamaha, had been sitting much of summer. Ran great 3 weeks ago, rpms 46 now rpms 33 tops. Cranks great and runs well, just no extra speed last 3/4 throttle. Checked the impeller and it looks good. Change the spark plugs? Had it stored last 3 weeks, would that do anything? Open to suggestions...

 

[ClassicAQ]

Anytime an outboard is to be stored for an extended period of time it should be drained of fuel, especially carb'd engines like yours. 90% of the time when outboards aren't performing up to spec it's related to a fuel system issue. This is especially true with carb'd engines. If you don't know when the previous owner pulled the carb's and jets for cleaning, and if you haven't either, that's the first place I'd start. Carb jet's have incredibly small orifices, and these orifices can become clogged over time. As they clog, less and less fuel over time can be delivered through the circuit. Less fuel delivery, less power, less power, less rpms, etc.

 

[99yam40]

agreed.
carbs will have fuel evaporate and leave a residue that can plug up jets/passages.

you can us a spray bottle with premixed fuel to spray into the carbs while problem is showing up to prove the problem is running lean, but if you have been out running this thing much, you could have already hurt a lean running piston so running it more is not something I would recommend.
compression, spark, timing, and fuel pump inspection would be something to check before removing carbs

 

[Sperkinsrn]

Thanks, appreciate the advice

 

[BaileysBoat]

4600 rpm is not running great, you're missing about a thousand.

 

[Sperkinsrn]

Thx, that's what I was thinking. Just had it on water a few weeks ago, consistently ran 46 rpm. Changed plugs and tried today. Pretty much same result, except tried to bogg down and cut off initially when under load. Thinking carbs, like y'all said. Any other thoughts?

 

[Sperkinsrn]

Okay, rebuilt carbs with kits, fired up 2nd try in big Rubbermaid container, warmed up great, idled at 10 instead of book specification of 8, otherwise great, revved easily to 58. Took to lake today and would idle at 8 and then knockoff, wouldn't run in gear long at all, tinkered with mini adjustment screw without result, got to run in gear when moved red emergency thingy to right one click. Would run over 13 rpm. Got home and doing same in Rubbermaid,(it is deep enough). Smoking a lot, checked plugs, which are new and they are black/oily. Please don't tell me my piston are toast, had the boat on the water one weekend since buying.

 

[Sperkinsrn]

Could wrong float settings be related to this?

 

[99yam40]

running with e switch to open will dump too much fuel once started and warmed up.
clean carbs properly and follow the Service manuals procedures to set everything everytime when you put them back on
anything hiding in the lines and pump can mess up the cleaned carbs very quickly

 

[Sperkinsrn]

Makes sense about e switch, so, get the repair manual and check carbs for junk and put everything back according to manual? You think Spark plugs looking black at tips and smoking could be from using the e switch and not damaged piston? Thanks for the help

 

[99yam40]

dumping extra fuel in cylinders is not good

 

[Sperkinsrn]

So, got online manual, took carbs apart, cleaned, put back together according to manual settings of float and other adjustments. Finally got it to crank with e switch open(I know not good but wasn't cranking without). Just for a few seconds, then turning e switch back. Got it to idle and even crank back up. But when it cooled off wouldn't crank again. Any ideas?

 

[99yam40]

If everything is set to spec then the carbs are not clean enough
did you remover the pilot screws when cleaning?

Did you remove the jets to clean?
did you follow the link and sync procedure when you put the carbs back on?
motor is not getting enough fuel at cold start up in automatic position, so that means enrichment system is plugged up or the carbs are

 

[Sperkinsrn]

Maybe enrichment system, yes, I took everything apart, twice now, soaked metal parts and sprayed what couldn't be soaked, rinsed, dryer with air. Ill look in the repair manual for enrichment system repair. Thank you