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I have a 1999 Yamaha 150hp EFI with a strange problem. Sometimes it runs fine and sometimes you will be running along and will loose RPMs. Motor doesn't die but RPMs go way down and then the motor picks back up and runs fine. Have taken it to two different dealers with no success. Have replaced bulb and used Seafoam fuel treatment with no success. I am looking for any kind of suggestions. Thanks for the help.
Kelly
my 150 pro v is doing the same thing... i replaced the plugs and the fuel filter..no luck...so i dropped it off today the dealer..I hope it doesn't cost me an arm and a leg
I wish both of you guys would try the "search" funtion on here... Search yamaha surging etc.. This could save you both a ton of money. Its probably the fuel pump diaphrams... Could be a bad fuel primer bulb. Pinched gas line, bad O2 sensor... Do you guys run ringfree or seafoam in your gas?
Let me know what you find. I have had two techs look at mine and can't find anything.
Thanks,
Kelly
I would trust some of the help/info here more than some techs... I can only speak for my area though... http://www.bassboatcentral.com/smileys/wink.gif
I just noticed tonight that my motor seems to do this a little, I think it's prop related in my case I just changed to a mercury Tempest prop, and I think it has something to do with the venting of the prop, I'm going to plug the holes and run it again.
If this happens after your holeshot and over 20-30 mph, It's not the tempest prop.
Please let us know what you find out and I'll do the same. My boat is at the dealer for the same symptoms. 2001 225 ox66.
So far I have changed out fuel pump assembly's, fuel filter, plugs, primer bulb, the gas, cleaned VST tank, and cleaned 02 sensor. Mine acts like someone turns the key off, then back on. If I ease on the gas I get the studders...if I mash on the gas, all is good.
This applies to those who have a stumble around 800-1500 rpm or during initial acceleration. This is related to LU shift linkage mainly because of bad clutch dogs or wore out shift arm. While on hose, put in gear and watch shift linkage connection to shift rail. If the linkage vibrates while accelerating itÂs hitting the cut out switch located next to the shift rail cutting out two cylinders. At higher rpm and heavier load this isnÂt noticeable but can be evident while hitting a bad wake or during rapid deceleration.
Also check for prop click and burned up LU lube.
Throttle Sensor Assembly was the culprit on my boat.
Where is this part located? Also thanks for the info.
TPS- throttle position sensor is located on port side on top throttle cam. Measure with multi meter and wire harness and it should be set @ .49-.51v at idle with smooth and gradual voltage increase (without spikes) while moving the throttle to 4.75v-5.25v at wot.
turns out i had a slit in the diaphram of the bottom fuel pump..changed the diaphram and allis good now