Yamaha 225 TXRS SWS 1994 misfires

[boatkev]

Seriel #62JU233 Motor misfires on 2 cylinders. I have new fuel, new filter, new plugs and clean carbs. Compressiion 110 psi +or- 2psi all cylinders. Cold engine starts and runs fine for about 1 minute and then won't idle and misses terrible on cylinders 2 and 5. 2,5 plugs don't get dirty. Thanks!

 

[Ray Neudecker]

Re: Yamaha 225 TXRS SWS 1994 misfires

Check your fuel pumps.

 

[boatkev]

Re: Yamaha 225 TXRS SWS 1994 misfires

Thanks Ray. I'll take a look.<br />Kev

 

[rodbolt]

Re: Yamaha 225 TXRS SWS 1994 misfires

hello<br /> if its the 3.1 L version otherwise known as the v76 there can be other issue. also check the plug cap resistance on all plug caps. post your complete model number or tell me if the t-stat hosings are vertical on the block or horizontal on the head. my book says the X model and the U model is 3.1 but it was made in both 2.6 and 3.1. about the only thing the two have in common is they are yamaha.if its a 3.1 its designed to drop spark on #2 and#5 or maybe it was 3 and 5, depending on RPM.

 

[boatkev]

Re: Yamaha 225 TXRS SWS 1994 misfires

rodbolt,<br />The model #225TXRS 1994 Salt Water Series. Seriel #62JUL233 This is a V76 model 3.1L. Thermostats are vertical. I do believe it is electronically dropping cylinders do to sensing a false high temp situation or maybe a bad throttle position sensor. ????<br /> Thanks for the reply.<br />Kevin

 

[rodbolt]

Re: Yamaha 225 TXRS SWS 1994 misfires

it drops two between 850 rpm and about 2000 rpm. the TPS and the temp sensor are both easy to change/check. if the timing locks at 7*BTDC the TPS may be bad, a bad TPS will not drop cylinders. overheat will not drop cylinders below 2000 rpm. I suspect you have a fuel problem and the ign is doing what it was desined to do. the temp sensor can be tested with the proer harness in place or in a pan of water with a DVM. if you dissconnect the knock sensor timing locks at 7*BTDC.if you try to run without t-stats odds are you will lean out #6 and smoke a piston. keep the t-stats.