put my rig in this am to chase some stripers, 800 or so yards out my engine cut back to idle speed just like you had pulled back on the throttle. Cranks and idles smooth, linkage looks good,oil level is good and water pump is peeing,but throttle will not advance.I am thinking a sensor is telling the ECM she is running hot or has low oil pressure. Any ideas on a DIY guy troubleshooting this.Am competent with a multimeter. She is a 2005 yamaha 115 TLRD.Never had a lick of trouble before.
Sounds like the Rev limiter. Check the pressure release valve aka popit valve. Upgrade it to the new style.
I would also put a new water pump and t-stats in it. If it has been used in a lot of salt the heads may need to come off and be cleaned.
Scout 185
Thanks looper, found the pressure relief valve on the parts diagram. Can you school me on what this part does and is there a way to test this part? only ask because it lists for 101 bucks. pulled the lower unit and removed the water pump assembly, will replace that and thermostat.
It also could be the sensor as you suggested. There is one on each side of the heads. You need a temp gun to test the running temp of the heads…
As for the popit valve, all you need is the plastic piece that looks like a mushroom. The old style has a T on both sides. The old style sometimes sticks in the rubber grommet. The new mushroom style butts up to the grommet and can not get stuck.
As the motor runs at higher speeds the water is run through that relief valve to cool the engine. This is because the water pump cannot move enough water to cool the engine.
That motor is not that old, but if it was run in salt its whole life I would strongly recommend pulling the heads and cleaning the jackets. Those motors are known for gathering salt and calcium deposits in the jackets. With it being a 2005 you should have no problem getting the bolts out. Once inside clean the tops of the pistons as well.
To do so you will need a torque wrench, and new gaskets.
If you don’t feel comfortable doing it we can take care of it for you.
Scout 185
none of the issues you are discussing will prevent the motor from coming out of idle. they will prevent running above 2200 rpms, and an alarm should be sounding.
with the motor NOT running, and in the neutral position, advance throttle to WOT position. is the control cable linkage causing the throttle arm on the 2 carbs to rotate the butterflies to 90 degrees?
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looper, you are close, but that’s not exactly what the pressure relief valve does.
the waterpump is a 1 to 1 ratio on the crankshaft. if the motor is turning 5500rpms, the impeller is turning 5500rpms. at that kind of RPM, the pump is producing MORE water than the engine needs, or can use, and the excess has to go somewhere, so the pressure relief valve opens, and allows the excess water to dump into the exhaust, and it does help cool the exhaust.
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Thanks Chris. I understood it wrong for a long time.
Scout 185
Chris, this is a 4 stroke EFI motor,The linkage was my first thought but everything appears normal although i will take a closer look. The relief valve i am looking at appears to be in the fuel system rather than the cooling loop. am i off course on thinking pump and injector rather than carb?
Sorry I thought it was a 2 stroke. Please disregard all I posted.
Scout 185
my fault, i think the f115 is what i left off the discription and this is what labels it as a 4 stroke
yeah, that little “F” at the beginning makes all the difference.
completely different motor, but still, none of the warning systems will prevent the motor from coming off idle, they still allow 2000rpms, but if the rpm reduction is activated, so is the alarm.
check the linkage the same way, just instead of 2 carbs, its 4 butterflies
very specific question…
is it idling at 900 or 750?
if its 900, you have a computer related issue, that’s its fault mode, idle at 900
normal is 750
VERY unlikely its fuel pressure related
if it was, as soon as you tried to advance the throttle the motor would bog and die
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Chris, I got back on the motor this afternoon and found the problem. The throttle control cable attaches to a rocker arm on the port side of the engine,at the top of this rocker there is a stainless rod that is threaded into the rocker and secured with a jam nut. The other end is knurled and appears to have been pressed into a spring loaded pivot fitting. I can press the spring loaded pivot arm forward and advance the throttle.This piece is located behind the air intake and is kind of tough to get to. Can you tell me what procedure you would follow to replace this part? I dont want to remove anything i dont have to but i dont want to make it more difficult than it has to be. Your advice will be greatly appreciated.
got it fixed this morning. the linkage snapped onto the ball fittings on the rocker arm and the spring loaded pivot. surprisingly easy.