2018 Yamaha 25 hp. 4 stroke will not run at slightly above idle.

[rkmnoles]

Motor sat on garage floor for 18 Mos. Before I purchased it from someone I know. I cleaned carbs, replaced fuel line and bulb and have fresh gas. Motor will start and run at idle. If you increase the throttle it will sputter and die. While running I can spray gas into carb while increasing throttle and it will run. Carbs have been cleaned no less than 5 times. Soaked and blown through. I am thinking fuel pump. It pumps when not under pressure but, my not under pressure. Any ideas? Thanks in advance .

 

[99yam40]

exactly how did they get cleaned 5 times?
not everyone thinks cleaning the same way

 

[Sea Rider]

Open tank's fuel air valve, prime the bulb till firm, release fuel pump's hose to carb, hook a proper container, maintain the motor ON while squirting fuel through the carb's throat, check if the fuel flow exits even with no hesitation whatsoever, if so, the fuel pump is working all right. If the carb was correctly cleaned, definitely it's not a carb related issue...

Happy Boatijng​

 

[rkmnoles]

exactly how did they get cleaned 5 times?
not everyone thinks cleaning the same way

They were disassembled and placed in a cleaning solution for 30 min. All openings blown through with compressed air and a small tip cleaner run the openings and then rinsed .

 

[99yam40]

They were disassembled and placed in a cleaning solution for 30 min. All openings blown through with compressed air and a small tip cleaner run the openings and then rinsed .

sometimes a heated sonic cleaner is needed to get everything cleaned properly.
sounds to me like the off idle ports have a problem

 

[rkmnoles]

sometimes a heated sonic cleaner is needed to get everything cleaned properly.
sounds to me like the off idle ports have a problem

I think I will try one of those as I hear the passages in a 4 stroke are extremely small

 

[rkmnoles]

sometimes a heated sonic cleaner is needed to get everything cleaned properly.
sounds to me like the off idle ports have a problem

A heated ultrasonic cleaner has been used to clean this carburetor and it is much better now. It will not give the burst of a two-stroke but that may be the nature of a four stroke. Any insight on a carbureted four stroke would be greatly appreciated.Runs great except for a fast hole shot.

 

[99yam40]

boat, load, prop are all part of what a motor can do.
are you sure you have the right prop for what you are using the motor for?

 

[rkmnoles]

boat, load, prop are all part of what a motor can do.
are you sure you have the right prop for what you are using the motor for?

I guess my question now is about throttle response on a four stroke versus the two stroke. After the ultrasonic cleaning it runs very well but does not have the immediate response the 2 stroke has. It seems to be a slower throttle response. This is my first 4 stroke so I am unaware of the differences.

 

[Sea Rider]

Is this motor a tiller steering or remote model ? How loaded do you usually go boating with ? Need to prop right the motor to run towards its max wot rpm range factory stated. For that purpose will need to install an induction tach, go for a wot run on flat calm water cond and report what's the max wot rpm the motor achieved. Once there will know how much wot rpm will need to be increased and that's with less prop pitches...

Happy Boating​

 

[dwco5051]

That 4 stroke weighs about 20 pounds or so more than the 2 stroke and some of that is moving parts. Physics says that force equals mass time acceleration so it will theoretically rev up slower than a 2 stroke of equal power but I don't know if it would be enough to notice. In the real world I would agree with the other posters that it may be a combination of load and the proper prop.

 

[Sea Rider]

In the real world I would agree with the other posters that it may be a combination of load and the proper prop.

Motors that comes with installed factory props, don't know if this the case are generally medium pitched, good for break in periods, soon after need to prop right the motor to run towards max wot rpm range, much better if propped right for fixed or near fixed loads.

Happy Boating​