96' Yamaha 150 Saltwater Series: 400 hours

[S2100]

Idles rough and often stalls. Occasionally has good spurts of idle power when all 6 are hitting but doesn't last long...just a second or two and then its idling rough again or stalling.<br /><br />When accelerating, the roughness goes away but when the RPM's come up to around 3000, and if you push the throttle any more, it dies--doesn't quit, just seems like when the butterflys open just a little bit too much, it loses all power. Feels like fuel starvation. If I leave the throttle way up for a a few seconds, the power surges up a little and way down as though the engine is sucking all the fuel down before the fuel system can re-plenish. <br /><br />It has fresh fuel pumps, filter, water sep, gas, plugs, and fuel bulb. <br /><br />Thanks in advance,

 

[rodbolt]

Re: 96' Yamaha 150 Saltwater Series: 400 hours

do you have a service manual.

 

[Ray Neudecker]

Re: 96' Yamaha 150 Saltwater Series: 400 hours

Definitely sounds like fuel starvation. Also sounds like the carbs need rebuilding. I would first test compression and fire.

 

[S2100]

Re: 96' Yamaha 150 Saltwater Series: 400 hours

Rod,<br /><br />Unfortunately, no. I haven't been able to locate the exact 96' manual however have been using an on-line generic version of a 98' 150 S/W. <br /><br />For "engine idles irregularly or stalls", I've checked: <br />Plugs<br />Fuel system obstruction<br />Fuel contaminated<br />Fuel filter<br />Spark plug gap<br />Ignition wires<br />Engine oil, (mix)<br />Fuel pumps<br />Choke knob<br /><br />The rest of the items are related to carburetor adjustments and throttle valve adjustments which I am reluctant to attempt myself. <br /><br />Any ideas?

 

[S2100]

Re: 96' Yamaha 150 Saltwater Series: 400 hours

Ray,<br /><br />How difficult is it to rebuild the carbs? I was an aircraft mechanic at one time and do have some wrench turning skills however am reluctant to try a matched set of three carbs.

 

[rodbolt]

Re: 96' Yamaha 150 Saltwater Series: 400 hours

they are easy, a crank position sensor,if used, will give about the same symptoms, you will lose spark on 3 and 4 if the sensor goes.<br />its rare but it does happen.<br /> most the time its bad pumps or dirty carbs.<br />biggest thing to remember is throttles fully closed does not mean throttles at idle.

 

[S2100]

Re: 96' Yamaha 150 Saltwater Series: 400 hours

Thanks for all the replies. I will post the outcome...<br /><br />See you out there,