can any one help?

[need help please]

i purchased a pair of 225hp yamaha foustrokes about a year ago and only recently installed them on my boat.. (grady white 265 express)... after the first run we realized there was tuning up to do and eventually we exhausted all the possible mechanics in my country(trinidad-caribbean)...after all the work we were left with one unsolvable problem. when we use the boat we often get it on plane and run at an average of 39 rpm on both engines.. sometimes we can coax the engines up to 50 50 rpm on both.. but what happens often is that the starboard engine cannot surpass 35rpm. and whenever i try to accelerate the throttle the rpm fades away to the 20s... this has not been solved by anyone in the country so far and i am desperately seeking your expert advice..please write back if you can help me with this problem as it can negatively affect the oher engine which has to drag the weight if the other less productive engine..some suggested problems by the mechanics were:
1. a faulty high speed stater
2. a faulty high pressure fuel pump
3. an injector problem

but these have not resulted in any headway....please help me... the ocean and fishing is my sanity. if i cannot fish as often as i like i will probably go insane..thanks in advance.. SCOTT MOSES

 

[cousinabe]

Re: can any one help?

check fuel system vacum, check fuel rail pressure at the trouble RPM.
either you have a restriction in the hull side ,the VST filter is clogged or an injector screen is clogged.

Here is some info on fuel system testing:
http://books.google.com/books?id=I2...+outboard&ei=u7WhSZuhOYL4lQSzr8yNAg#PPA124,M1

Some info on cleaning the VST:
http://books.google.com/books?id=I2...+outboard&ei=u7WhSZuhOYL4lQSzr8yNAg#PPA236,M1

 

[rodbolt]

Re: can any one help?

stator is out and dont go back to that tech as its obvious they are totally clueless.
the F225 uses a TCI ign which is battery powered and does NOT rely on stator charge coil outputs for any ign source.

check the filter in the VST tank, most likly you will find that tiny screen stopped up. you may also have a small inline filter between the lift pump and the VST inlet,depending on year model, that can clog as well.
easiest method is to simply install the fuel pressure guage on the fuel rail and monitor fuel pressure.
if it cannot maintain 35 PSI then go find out why.
either the VST cant get fuel or it cant deliver it.
you could also have an injector filter clogged but it doesnt quite fit your problem description.