Re: 2001 Yamaha F115
with the basics.<br /> always remember, suck,squeeze,bang and blow. <br /> everything on the motor helps do it at the proiper time.<br /> fisrt have a leakdown test done. its much more accurate than a compression test. a compresion test is acceptable however not as accurate. to test the compression on that motor pull the stop lanyard to kill the fuel injection and open the throttles to WOT.<br /> buy a service manual.<br /> study the service manual.<br />some of the tools a large auto parts store will carry. <br /> you will need to check fuel rail pressure at the misfire RPM. you will need to test spark at the misfire RPM.<br /> the ign system on that motor is fairly simple. the coils fire in pairs. 1 and 4 fire simultaneously as do 2&3. its a CDI waste spark ign system. you will need a timing light. certain sensor failures can cause the ign to lock the timing. you will need various test harness's to test the crank position sensor and the throttle position sensor.<br /> while I applaud wanting to fix it yourself and I do understand your delima its usually better to allow a certified,competent tech test the system. however finding one is getting harder and harder. most tend to forget the basics,plug in the laptop and get all confused when the lap top says nothing is wrong. I like the laptop. it gives me a rapid test on what is not wrong. keeps from chasing shadows. I have found that other than telling me what is not wrong most times computer diagnostics on the yams is a waste of time.<br /> do you have the yamaha multifuntion gauge? if so is any visual alarms indicated? a quick test to isolate a single cyl is to back the boat overboard and moderatly load it on the trailer, 200 rpm or so, then one by one remove and reinstall the fuel ingector connector. watch the cyl rpm drop for each removal. the one that has no effect is the cyl that may be the problem. if all have no effect or the same effect its time to hunt what is common to all affected cylinders. <br />the cause of a misfire can be almost anything. start with the basics. also start with a service manual. read it .<br /> try to understand how each subsystem works with the other and why. that EFI 115 has to perform the same functions as the motor orville and wilbur flew with. its not changed at all. just the controls got more precise. intake, compression, spark at the correct time and exhasut and it runs. if any are off it may run but run poorly if any are missing it wont run at all. I can usually run a diagnostics on that motor in an hour to an hour and a half. if you have the manual and dont trust your tech make a list of all sensor values and coil inputs and test specs and give it to the tech and say I want all this tested. I will agree to many techs are rather incompetent anymore. its getting worse each year.
