Rev limiter

[Baystalker]

Not long after a service on my Yamaha 100 4 stroke I was asked if I hit the rev limiter I know in automotives that a limiter will cause the engine to maintain rev's but with no power or torque.

Question is I have never heard or felt the rev limiter on my outboard, some may say this is great but I guess the next question is am I getting the most out of my motor

When you have hit the rev limiter what does your engine do (if anything)

[jyasaki]

I'm pretty sure I've hit the limiter on my F115. Doesn't really feel like anything. Revs just stay around 6100 or so.

jky

[Baystalker]

thanks jky, when you say you didn't feel anything did you come to a point on the throttle control where it made no difference to the rev's or power. Like I am under the 6000rpm around 5500-5800 and even though there is around 1 inch of throttle left on the control it make no difference.

[jyasaki]

Yes, it spooled up to 6100 or so, then nothing more. No lurch, no missing, just felt like a motor hitting max rpm (perhaps a bit earlier in the throttle travel.)

jky

[Mr. Demeanor]

Doesnt sound like either of you have hit the rev limiter. Most rev limiters are electronic and cut out ignition when you reach a maximum rpm. This way, for instance, if your running wide open and you throw a prop the motor doesnt spin to 8k rpm and come apart. I can hit my rev limiter with a light load and it just sounds like the motor starts to miss. The likiter is usually set a little higher than you maximum recommended rpm operating range and if your hitting it, you could probably go up one size in pitch.

[sharkfisher]

[Glen E]

I would agree with Mr D...it's an ignition cut and on a Merc smartcraft system you get an "overspeed" indicator....

[MarkGW]

Actually I think that electronic ignition rev limiters simply retard the timing to reduce power output. All cylinders still recieve spark to burn off the fuel, rather than allowing the raw gas to wash the cylinder walls, and yes the combustion process continues past the opening of the exhaust vave opening and into the exhaust system. You shouldn't notice it in a modern engine, meaning less than 10 years old. You may be able to check it by spinning it up untill advancing the throttle position does not increase performance, and marking that spot on the throttle control. Then, when at the dock w/o engine running, advance the throttle to that position and physicaly verify that the throttle plate, in the throttle body is wide open, or not If it was wide open then you probably did not hit the limiter, but your throttle linkage is at WOT before the control hits the stop. Don't bother to fix this as it is not an issue. However, if the throttle butterflys are not at WOT in this position you need to push the throttle control to the stop and , again, verify that the throttle butterflies are at WOT. If not, you need to fix this. If so, then you probably hit the rev limiter, and your engine may be making more power than your prop can use.
Get the drift?

[mlee]

The ECM on a HPDI or a four stroke yamaha records the number of times a motor hits the rev limiter [which on an HPDI keeps the motor from going past 6200 or 6250]. Just plug the motor into the Yamaha Diagnostic Software and the story is told. It is sort of an indication of how hard the motor is run. Such as running hard into rough seas and airing the prop.

Think of it like this-- if you were in a race car and were running wide open--and mashed the clutch with your foot still on the gas---you'd probably blow the motor. A boat motor running hard and going into the air is just like mashing that clutch. The rev limiter function of the ECM cuts out cylinders and keeps you from blowing the motor.

[Baystalker]

Interesting stuff there guy's thanks.