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Tomfoolery wrote: And grab an old umbrella, even a small Totes type, and store it somewhere. Hang it under the OB when you change the prop, even in the water if you have to, to catch the nut and/or washer and/or cotter pin and/or wrench when (when!) you drop one of them.

More good advice. Love this forum.

Actually I was going to change the prop from a cheap rubber dinghy parked under the raised motor: I think I could squash the rubber down enough to get it under the lower unit and then lower the motor and hold the dinghy in place. Or maybe pop it, I don't know.

Reminds me of when I made the brilliant decision to adjust a sidestay while anchored out. I was being so careful not to drop the pin that I dropped the pin...it bounced down the cabinside and somehow snagged on the chainplate without going overboard. It's been a while since I checked my spares kit...almost sure I have a few pins in there but note to self: check!

I have serviced the prop from an inflatable tucked under the outboard shaft. It worked pretty well.

The umbrella sounds interesting...

Yup the dinghy worked just fine. What didn't work was that the freakin' dealer gave me the wrong size propeller. It fit on the hub but didn't fit over the thrust washer. What a total waste of time.

Well, heading out to the beach tomorrow with the 17 pitch prop...at least I can give a prolonged test report on that wrong propeller.

So once again I reach out to the forum: is there anything wrong with running at 3,000 RPM at full throttle for extended periods?

Yes, bad for the motor. Very bad.

Kind of like driving a manual shift car in 5th gear at 10 mph floored.

Starscream- Do I have this right; you have a brand new E -tec, not broken in yet, and you have been running it with a prop that allows you a max RPM of 3000?

I would not do this without knowing more about the engine. Even at lower RPM it over-loads and bogs the engine. If you have any problems with the engine in the future, an engine history printout will reveal that this was done (throttle position sensor shows out of spec for RPM etc) and possibly void your warrantee.

Note that doing this would ultimately destroy a conventional outboard engine of previous generations, it is not quite half (?) of the recommended RPM range.

The E- tech computer does run the engine oil-rich (and compensates in the fuel mixture) for the first half-hour or so, during break-in, which might work in your favour.

Now, having said all of this... I am curious...Did the motor sound and appear to be running OK at lower RPMs? Direct injection (in cars it's the same thing) is by its nature noisier, and gives a sound that you would normally associate with pinging, or detonation (as if the octane rating of the fuel is too low, or like marbles are rattling around inside the engine). Maybe even diesel-like.

If you haven't noticed anything unusually excessive with this, the computer must be adapting ( a lot of things, such as retarding the spark timing, injector timing and duration, scavenging etc) to keep things running cool.

Not to sound too hysterical about this, but you should know that bad things can happen, and you are running some risk in doing it. What does the manual have to say about it? Mine is with the boat so I can't check.

-B.

EZ wrote:The umbrella sounds interesting...

This came from my FIL, who paid for that lesson the hard way, several times over, in his early days of boating as I understand it.

Starscream wrote:So once again I reach out to the forum: is there anything wrong with running at 3,000 RPM at full throttle for extended periods?

I wouldn't do it, for the reasons already given. Brand new engine? I wouldn't do it to an old engine that someone gave me for free. Hurts my sensibilities.

My initial run was for maybe 1 minute at full throttle, which was enough to realize that it was the wrong prop. I haven't run it since then and am going back to the dealer this morning for another prop...hopefully one that fits this time.

I kinda figured it was a bad thing to do so I haven't run it since that initial test. Good thing it was windy and wavy so the temptation to sail overcame the temptation to play with the new motor. If it was calm I probably would have run it longer. Dodged THAT bullet.

Changed to 14x11 prop and now 21mph at 4800rpm. Full ballast, 5 people and beach gear. I think a 13x11 might be a better choice?

Much easier to see over the bow...actually if I sit on a fender I can see where I am going at full throttle. Good call on the wedges.

The motor is quieter than the BF50 but only marginally. The real difference becomes obvious at 3500 RPM when you are still running in the high teens mph.

That's sounds like a heavy loaded boat. Good speed with ballast. I would leave it alone. Try it without ballast and maybe 3 to 4 people and see what the speed and rpm are before messing with prop again. I think 5000 rpms is the recommended rpms.

Take Fouz's advice first, but then try a 14x9. If you're trying to increase RPM, you want to reduce pitch, and a 14x9 should give you another 400 rpm or so.

Also consider that the stock ETEC tachs are not that accurate. Mine is 400 rpm lower than what the ECU directly reports. Consider hooking up a Lowrance ETEC NMEA-2000 cable to your chartplotter to see true engine performance (and fuel usage and other goodies). It's $50 bucks on ebay and one of the most worthwhile mods out there.

Starscream wrote:Changed to 14x11 prop and now 21mph at 4800rpm. Full ballast, 5 people and beach gear. I think a 13x11 might be a better choice?

Evinrude's prop schedule shows prop diameter going up as pitch goes down, which has a certain logic behind it from where I sit. Shallower pitch is generally for slower boats and/or heavier boats (for a given hp), which is manifested in force of the blades against the water. You don't want to use a steep pitch on a small propeller to get the needed force as there will be too much slip and loss of efficiency and possibly cavitation, too. If that engine swings a 14" prop, then use a 14" prop.

I would figure out how you're going to use the boat (ballast in, many folks, loaded with supplies, vs bog stock empty with no ballast), and select a prop to keep the engine in it's design speed range of 5000-5500 rpm (shoot for the middle). If the two configurations are going to be a regular thing, then get two props - each one the best for that configuration.

If you only want to have one, then I (and this is just me talking) would use a prop that puts the engine in its sweet spot with ballast and lots of folks, and just be careful about engine speed if/when running without ballast. That engine probably has overspeed protection, but I would be careful about controlling engine speed anyway.

And that's a good point about the tach - it's critical that the prop be matched to engine speed at WOT, but if the factory tach is notoriously imprecise, then an independent means should be employed to calibrate the tach. Lugging the engine is bad, but you won't know for sure what it's doing if you can't rely on the tach.

And that reminds me - I don't actually know if MY tach is accurate. I have a couple of hand-held tachs, one that's mechanical, and the other using a photocel of some sort. They normally agree very closely with each other, when I've compared them, and they're also both very close (within a few rpm) to the unloaded speed of an induction motor, which is just a hair under 3600 rpm for a 2-pole motor on 60Hz power.

So maybe I'd better check my tach, while it's sitting here in the driveway, and it's easy to get to the flywheel.

Think I will try a 14x9 as Mastreb suggests. I was going to try a 13x11 to get the extra RPM's but I prefer to follow smart guys' advice.

My "chartplotter" is only a Humminbird GPS/down-imaging sonar...it has an NMEA GPS ouput and I have wired it to my DSC radio for position reporting, but that's the limit of its capabilities. So I don't think there is a simple way to get real RPMs. Maybe I could try a strobe at night with someone hanging over the back seat

The manual says 4500 to 5500 RPM full-throttle operating range, so I am right in there with the 14x11 but I'd rather be closer to 5k or 5.2k RPM I think. The change in pitch from the 17 to the 11 brought an additional 300 RPM/in.pitch so the 14x9 should hit 5100 or so.

I'm not understanding the idea of changing the prop. Sounds like you got lucky and got it right on.

With your current prop.
Ballast in, heavy loaded, 5 people. 4800 rpms. Recommended.
Ballast out, light load, 2 people. I think you may be a little over the 5500 rpms or right at it. Don't know yet. Recommended.


With a smaller dia or less pitch.
Ballast in, heavy load, 5 people. Lets assume 5100-5200. Recommended.
Ballast out, light load, 2 people. You will be over the range in rpms. Not Recommended.

Or am I missing something

But I would do like mastereb said and check the rpms by another means