92 115 yamaha stalling,fuel restriction?

gentlemen I recently purchased a boat with a bad gas tank and a low hours 115 yam the console was detached I replaced the tank with a plastic moeller brand 25gal and reattached the console the motor fired right up upon first lake run it was ran strong for aprox 45mins then seemed to pull back as if starved for fuel or at 3/4 throttle upon inspection there was trash in the filter rubber particulates I then replaced the old fuel line and re-routed to eliminate possible pinch in line also added a in line filter (plastic cone shaped with a cartridge )it was in the marine fuel section not an automotive type in sequence with the existing that had a bad gasket at the filter ,this seemed to compound the problem it acted like it was getting air in the lines we could see bubbles in the inline filterthought maybe the tank inlet was floating or not enough fuel in the tank 3rd time out I re-routed the vent it was full of fuel in a low spot ,removed the inline filter installed new factory filter filled the tank with a short mix aprox 60:1 instead of 50:1 miscalculation on my part she ran good and strong out of the hole the backed off to 3/4 throttle 4th time strong again out of the hole then backed off and then died was able to restart 3 times limped back today I checked the compression 90psi each cylinder checked the fuel pump no tears seemed a bit corroded at the motor to pump area,and maybe a little loose there are no thermostats in place on either head need some help thanks G

Re: 92 115 yamaha stalling,fuel restriction?

You need to buy a cheap vacuum gauge at autozone, or wherever and put just in front of engine mounted filter, vacuum should be about 2"(or less) at IDLE and never, ever more than 5"(4 or 4.5" in my book) at WIDE OPEN THROTTLE. Do this and let us know...then we'll see why.

Re: 92 115 yamaha stalling,fuel restriction?

I,ll try that what about the compression the motor was cold and the carbs were not open which method do you recomend?

Re: 92 115 yamaha stalling,fuel restriction?

I,m going to rebuild the pump this weekend ,next question will running without thermostats affect the performance and or set off any shut down devices?I,m in Dallas area water temps are aprox mid to low 70s

Re: 92 115 yamaha stalling,fuel restriction?

On the vast majority of motors the throttle doesn't affect the compression, but on a few(F25 for one) it really does....yours it won't. Air will flow through in a few revolutions enough as long as comp. gauge has checkvalve, it'll build to reading....you do NOT want to run without thermostats, why would you do that? It will affect performance, won't cause any alarms, but will allow carbon to build much faster in engine, plugs, than should....outboards already run cooler than engines like to run, don't compound one of the hurdles the engineers already have....please get a vacuum gauge and use it as described, without proper diagnosing you'll be chasing this wild goose with $$$.

Re: 92 115 yamaha stalling,fuel restriction?

finally got around to testing the pump and installing thermostats the pump was reading at 1 3/4 at idle I never got to test full throttle just replaced the pump and it does not die out but same problem starts out strong then quickly falls back as if a govenor has kicked in almost like the vacume advance is not working or carbs? what should I do next? I believe all the fuel to motor problems are solved it must somthing else?