WOT

[omc man]

I have a 97 Johnson 50 horse and I just installed a tach, is wot 5500 rpms, and is this what I should try to run the outboard on all the times, or is this like the redline on a car, when it is ok to run less rpms, but 5500 is the max I should run? Thanks

 

[Dhadley]

Re: WOT

5500 on that motor is border line lugging it. I sure wouldnt recommend setting it up at any less. Personally for longevity I'd set it up closer to 6000 if it were mine.<br /><br />You can run a properly set up 2 stroke at any rpm you chose for as long as you like. You will find a range thats best suited to your comfort and the motors best fuel consumption depending on your boat and load.

 

[cobra 3.0]

Re: WOT

...so you need to use a lower pitch prop to achieve a higher rpm.

 

[Dhadley]

Re: WOT

Actually with an outboard we would rather change (optimize) the set up first. Going to a lower pitch is a last resort. Basically we concentrate on reducing the slip which increases efficiency overall.

 

[Mark42]

Re: WOT

Just my $0.02...<br /><br />That '97 Johnson is pretty much the same as the '93 Johnson/Evinrude that I have a service manual for. OMC lists the full throttle operating range as 4500 to 5500 max for the 40 and 50 hp models. The rev limiter in the power pack is set at 5800 (even though they list rpm limits of 5700, 5800, 6100 and 6700 depending on hp and model, they seem to actully be 5800). <br /><br />I would suggest you get the proper manual for your year motor and follow OMC's recommendations. You may not be able to get that motor up to 6000 rpm, at least not in '93. So it is important to have the correct info before making decisions/changes.<br /><br />I was told that there is no way the 40hp had a 12 amp regulated alternator (it does), that it should run in excess of 6000 rpm (it can't) and even Teleflex lists the tach pole setting wrong for this motor (it's 6p for the 12 amp, not 5).<br /><br />Just be sure you have the correct info. It will save you mucho headaches. And remember that even OMC has errors in their info (it has been suggested that the 6700 rpm limit is a typo and should be 5700). So double check. <br /><br />I have both the Seloc and OMC manuals. I prefer the OMC for detail and accuracy.<br /><br />Mark

 

[omc man]

Re: WOT

Thanks for the replies, sorry I couldn't respond till today, When I was testing the boat out, it was doing 5500 at around 3/4 throttle, I think it would easily do 6000rpm, I was just afraid to push it didn't know if I would damage the motor. Before I had a tach, I ran it a couple of times at full throttle, and the engine was winding pretty tight, this is with the motor trimmed all the way down, I'm afraid the prop has too little pitch, and it does not have any numbers or pitch and diameter markings

 

[omc man]

Re: WOT

Thanks for the replies, sorry I couldn't respond till today, When I was testing the boat out, it was doing 5500 at around 3/4 throttle, I think it would easily do 6000rpm, I was just afraid to push it didn't know if I would damage the motor. Before I had a tach, I ran it a couple of times at full throttle, and the engine was winding pretty tight, this is with the motor trimmed all the way down, I'm afraid the prop has too little pitch, and it does not have any numbers or pitch and diameter markings

 

[Indymike]

Re: WOT

Dhadley could you expand on the set up thing a bit for some of us newbies.<br /><br />Thanks ,<br />Mike

 

[wilde1j]

Re: WOT

X dimension (height on transom), kickout, motor running perfectly, etc., then try pitch change. OMC, if you're already over 6000 RPM WOT, you will need to increase pitch to get to ~ 5800 WOT. By the way, Dhadley knows, so pay attention to what he says. See what the motor does at WOT and go from there. This is not about what the motor might do, but what it actually does at WOT. Where you chose to run it after it's set up to turn ~ 5800 is your choice!

 

[Hotrods]

Re: WOT

Yes plz Dhad, My manual calls for 4500 to 5500 max rpm. I am just tippin 5500 on the 93 115 rude? (still in break in).

 

[Stumpknocker]

Re: WOT

Dhadley, <br /><br />5500 on that motor is border line lugging it. I sure wouldnt recommend setting it up at any less. Personally for longevity I'd set it up closer to 6000 if it were mine. .<br /><br />I run a 95 48 SPL. WOT=5700-5800. I was told years ago to drop back about 25% for cruising. I assumed running the motor at top speed would be cruel and unusual punishment in violation of the 8th Amendment to the Constitution. I understand I get better fuel economy at a slower speed.... but what did you mean by the statement border line lugging at 5500? So running WOT isn't a bad thing for long periods of time? Learning curve in progress. <br /><br />My engine will scoot me along at 31 topped out. I cruise it at 20. Wouldn't this increase the engine life rather than running it wide open?

 

[Johnshan1]

Re: WOT

As Wildeone said, run it however you want, but make sure when you hit the throttle wide open it hits the correct max RPM range. <br /><br />In other words, you want a prop that will allow you to run in the max RPM range at full throttle. If your prop didnt allow you to access this range, you would be lugging the engine.<br /><br />Correct me if im wrong but thats my understanding,<br />-John

 

[walleyehed]

Re: WOT

Propping to load the engine to a specified RPM, such as 6000, allows the engine to operate "cleaner" in a sense.<br />Dropping back to cruise is no problem if you're propped for the correct WOT rpm.<br />You don't want your "cruise" to be at 4500rpm if it will only spin say 4800rpm, on the other hand 4500-4800 would be an excellent cruise if you are propped for 5800-6000 WOT.<br />Running WOT for any length of time you want is OK, as long as it's propped for the top of the RPM range.<br />I'm not DH, nor do I have the qualifications he does, but I do see the same results DH has dealt with on many of these issues.

 

[Stumpknocker]

Re: WOT

Thanks guys, I top out at 5800 and cruise around 4400-4800 20-22 mph. I feel like the engine just wants to run there all day long. Sort of a groove it gets into... hard to explain. Its difficult to keep it under 20, as it just wants to creep back to this speed of 20-22. So... I let it have its way. Gets great fuel economy here and although I'm certainly not the fastest gnat on the water, I do most certainly get there eventually. That is after all the name of the game... to get there and back.... at least I think it is.

 

[lark2004]

Re: WOT

What if the engine was made to run 4000 to 5000 RPM, I have an old Evinrude Lark 40hp (68 model) that I am rebuilding, can the engine be run at a higher RPM safely?

 

[omc man]

Re: WOT

Thanks so much for the replies, I'll get to the lake as soon as I can, will it be ok to run the motor up as far as it will go, even if that is to 6700 rpm or what the powerpack limiter is? I pretty sure I saw 5800rpm the other day, so I think the limiter must be set higher, as it never cut out thanks

 

[omc man]

Re: WOT

Thanks so much for the replies, I'll get to the lake as soon as I can, will it be ok to run the motor up as far as it will go, even if that is to 6700 rpm or what the powerpack limiter is? I pretty sure I saw 5800rpm the other day, so I think the limiter must be set higher, as it never cut out thanks

 

[Stumpknocker]

Re: WOT

Well as I didn't get an answer ref to the engine life of an outboard at high rpms vs low rpms... I went to an OMC mechanic. He advised that all engines... two stroke, four stroke whatever.... will last longer at lower rpms. Outboard Inboard motorcycle car truck yo yo whatever. He was firm about this. It should be properly setup and propped. It should have adequate lubrication and be well maintained. All givens. It was suggested cruising at about 25% of full power is a good place. And as posted earlier by several.... lugging is very bad.

 

[Stumpknocker]

Re: WOT

I agree... save your fuel and get where u is going. Enjoy the scenery too.

 

[walleyehed]

Re: WOT

If your mechanic told you lower the R's for longer life of your outboard, I will be "FIRM" in telling you he doesn't know 2-strokes AT ALL.<br />25% of "full-power" wouldn't be on plane yet, so I will assume you meant "reduce" power by 25% for cruise....which is great, "IF" you are propped to the High-end of the range to start with.<br />Actually, 60-65% of full-power (35-40% reduction) is best fuel economy if at or near max HP rating of boat.