30hp esrq loosing 10 mph (Yamaha)

[deltacottonboy12]

Hello all. i've used this site for numerous fixes on my outboards. I've read and read for this answer ans cant find quite what im looking for.

As in the title, my motor is a 30 HP Yammy ESRQ. My motor runs well, but isn't quite getting to max rpm( per my ear). Today i cleaned the carbs and had some gunk in my high speed jets. cleaned them, rebuilt the carb and took her to the lake. same problem. The motor is running well, but not achieving full speed/rpm. The boat runs 29-32mph with me alone and right now its only hitting 21 mph. so obviously something isnt right.

A boat mechanic suggested the air/fuel mixture could be off. The plugs are running a bit rich. The bottom is richer than the middle and middle is richer than the top cyl.

he told me how to adjust them but i dont "hear" the motor dropping and raising rpms unless i lean the heck or rich the heck out of it. im puzzled.


where did my 10mph go??

any ideas guys? i have no manual.

 

[bag007]

Re: 30hp esrq loosing 10 mph (Yamaha)

Did you fully rebuild the carbs... replaced all the needles the they may be worn hence no change until you goet very lean/rich.. also when you trun the needes you should wait at least 30 sec befor you notice a change... I didnt belive this at first until I saw the mechanic at a ocal marina do it on a motor there..... you still may have dirt in the high speed jets too.. It took me two tries last time.. mainly because the dirt was in the fuel line too so it pushed more crap in there...
Also you may need to link sync the carbs too. You really need the manual for that.

 

[Mas]

Re: 30hp esrq loosing 10 mph (Yamaha)

Could possible be a spun prop if she is "running well!?", as well as carb & ignition issues. Fresh gas? Water logged boat?

Mas

 

[deltacottonboy12]

Re: 30hp esrq loosing 10 mph (Yamaha)

Did you fully rebuild the carbs... replaced all the needles the they may be worn hence no change until you goet very lean/rich.. also when you trun the needes you should wait at least 30 sec befor you notice a change... I didnt belive this at first until I saw the mechanic at a ocal marina do it on a motor there..... you still may have dirt in the high speed jets too.. It took me two tries last time.. mainly because the dirt was in the fuel line too so it pushed more crap in there...
Also you may need to link sync the carbs too. You really need the manual for that.

i rebuilt the carbs again today. did a thorough cleaning. the high speed and low speed jets are clean. wire cleaner through them, soaked them and compressed air.

The Link and sync, this is something i have tried reading about. i have found some info but not quite what i'm looking for. i'll need to purchase a manual for sure.

no spun prop. its not spiking in rpms with loss of speed. Its accelerating great, sounds just as it should, but its just not hitting that "next gear". its sitting at 21-22 mph and this same motor last year was running 29-31 last year. same boat.

i discovered 2 leaks in my gas line from the tank to the motor. could this be the culprit? i know this needs to be replaced, and will be, but could this cause the motor to not get the fuel needed to reach that rpm?

The plugs are a hair rich as well.. the link and sync should clear that up..

thanks for the input guys. i know its tough to diagnose something over the web. i'm doing my best to describe everything..


Thanks again.

 

[99yam40]

Re: 30hp esrq loosing 10 mph (Yamaha)

Fuel line leaks on the suction side of the fuel pump can pull air into the system and that could cause the problem of not getting enough fuel into carbs at WOT
Especially the upper ones because that is where the air bubbles tend to go (bubbles rise upward)

 

[deltacottonboy12]

Re: 30hp esrq loosing 10 mph (Yamaha)

Fuel line leaks on the suction side of the fuel pump can pull air into the system and that could cause the problem of not getting enough fuel into carbs at WOT
Especially the upper ones because that is where the air bubbles tend to go (bubbles rise upward)

when you say suction side, i will interpret that as the line from the gas tank to the motor?

 

[99yam40]

Re: 30hp esrq loosing 10 mph (Yamaha)

that is correct leaks on the pressure side will leak fuel out not suck air in