WOT RPM is too high when the load is light

[rejesterd]

I have a 2011 F50 engine on a 16' aluminum deep V hull. Typically, it's just me or one other person on the boat with me. I didn't note the WOT RPM when another adult was in the boat, but when it's just me, I'm seeing 6200-6300 RPM. The manual says I should get a max of 6000.

Does this mean I need to get a prop with a higher pitch? Or is it safe to keep my current prop (10 5/8 X 12) and just lay off the throttle a bit? What kind of damage can come from revving the engine beyond 6000 on a consistent basis?

Thanks.

[boscoe99]

What you are seeing is completely normal. If the motor is propped correctly (able to run at or near 6000 RPM with the boat loaded) then it may very well exceed the red line RPM (6000) when the boat is less than loaded. It is the operators' job to not let the motor exceed 6000 RPM.

Your car can exceed the speed limit when going down a steep hill. Who's job is it to manage the throttle? What will the policeman say when he is writing out the ticket?

If the motor were to be propped to below 6000 RPM with just you in the boat on a cool, dry day, then on a hot and humid day, with other folks and stuff in the boat, it may very well be over propped. Over propping can result in poor performance at best and engine damage at worst.

Folks that are over propped, and who have poor performance, come here all of the time looking for more power. When what they really need is the correct propeller. Don't be one of those.

Here is what the owner's manual says.

[pstephens46]

Boscoe: Does that motor have a rev limiter? If so, shouldn't it kick in about 6200 rpm? That doesn't mean run it until it hits the limit and then back off.....just asking.

[boscoe99]

Yes, that model has a rev limiter.

To protect the motor when the operator is not doing the operator's job of minding the throttle.

Actually, so many Yams are over propped I am surprised that Yam bothered to put a revolution limiter in the motor. For those few that don't care if the motor over speeds, if and when it will, if something bad were to happen they would get what they have coming to them. Barking the propellers and running on the rev limiter come to mind.

[rejesterd]

Thanks. I certainly laid off the throttle when I started noticing it, I was just wondering if I still needed to get a different prop pitch to avoid damage over time. If I still see it creep over 6000 with a full load at WOT, then maybe I'll change the prop. Otherwise, I'll just monitor the rpms manually and lay off when needed. Seems like installing a rev limiter would be a little more money than it's worth. If I already have one installed, it's obviously not working (or the tach is way off).

[rejesterd]

Yes, that model has a rev limiter.

To protect the motor when the operator is not doing the operator's job of minding the throttle.

If that's true, then my rev limiter apparently doesn't work or my tach doesn't work.. otherwise, how would I see RPMs rise above 6000?

[pstephens46]

Rev limiter probably doesn't cut spark until 6200-6300.
I wouldn't try to find it! On purpose.

You could run the motor with a laptop and software if you wanted to compare tach to ecu.

I wouldn't change the prop. Bet it is pretty efficient at lower rpm ranges.

Do you really run at WOT that much?

[boscoe99]

If that's true, then my rev limiter apparently doesn't work or my tach doesn't work.. otherwise, how would I see RPMs rise above 6000?

The red line (not to exceed) RPM is 6000.

The rev limiter kicks is at or about 6200 when the operator is not paying attention. It also acts as a wake up call.

Tachometers are not always spot on.

[rejesterd]

The red line (not to exceed) RPM is 6000.

The rev limiter kicks is at or about 6200 when the operator is not paying attention. It also acts as a wake up call.

Tachometers are not always spot on.

Great, thanks again. So I think I'm all set then.. just lay off a bit when it approaches 6000 like I've been doing. The hole shot and top speed feel just fine to me, so no reason to switch the prop at this point.

[rejesterd]

Rev limiter probably doesn't cut spark until 6200-6300.
I wouldn't try to find it! On purpose.

You could run the motor with a laptop and software if you wanted to compare tach to ecu.

I wouldn't change the prop. Bet it is pretty efficient at lower rpm ranges.

Do you really run at WOT that much?

No, I don't run at WOT very much at all... I was just WOT-ing last weekend to clear off the fogging oil from the winter and noticed it went over 6000. Now that I understand how the rev limiter works, I think I'm all set. No need for a new prop. Though it couldn't hurt to compare the tach output to YDS output. Thanks.

[99yam40]

Next time it is in a shop have them verify the Tach with a shop tach just to be sure