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Thread: Running outboards WOT

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    Member Yukoner's Avatar
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    Default Running outboards WOT

    So is it "hard" on an outboard to run it wide open for extended periods of time?
    Looking at the RPMs they pull versus a skidoo or roadbike, they certainly aren't near as high, although they are under constant load.
    My grandfathers old 25 Johnson on his 20' river boat would take him from Dawson to Whitehorse running wide open all day long over 4-5 days, and it seemed to last for ever.
    Any thoughts?
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    Member tlingitwarrior's Avatar
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    Quote Originally Posted by Yukoner View Post
    So is it "hard" on an outboard to run it wide open for extended periods of time?
    Looking at the RPMs they pull versus a skidoo or roadbike, they certainly aren't near as high, although they are under constant load.
    My grandfathers old 25 Johnson on his 20' river boat would take him from Dawson to Whitehorse running wide open all day long over 4-5 days, and it seemed to last for ever.
    Any thoughts?
    Only time I run mine WOT is at the end of a trip. Unplug the gas, run WOT to blow out the carbon and burn the fuel in the lines. I have a hard time believing running any engine at WOT for an extended period of time is "good".
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    Member Bob the fisher's Avatar
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    I run my Mercury 200 Opti (with the sport jet) WOT most of the time. Mine is a DFI two stroke and I was under the impression that you are supposed to run them WOT. Any comments on that?

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    Member Dupont Spinner's Avatar
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    My belief and some personal experience that an engine that is running at a constant rpm many times with good maintenance will far out live one that cycles (shifting) thru the rpm range. Even running in the upper limits.

    My sleds run north of 8 grand and I get thousands of hours of use and they run variable but mostly closer to max rpm. Generators run at max rpms constantly for thousands of hours.

    One reason I believe this to be correct is you maintain constant combustion temperatures and it allows carbon to burn off and not accumulate.

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    I was told many times by Rocky at Rocky's Marine that you definitely are NOT supposed to run WOT all the time. The real saving grace here is that 2-strokes are tough engines.

    I disagree that generators run at max RPM constantly. They might run at a constant RPM but not max. Next time you're around one find the little throttle and give it a push. the RPMs will go up.
    I'd agree with you, but then we'd both be wrong.

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    I guess its how much fuel you want to burn and how loud you want it in your boat when your running... Next time out do some math if you drop down your RPM's and watch your speed on GPS you will find a sweet spot at some point your gonna just be making a lot of noise and burning a lot more fuel...

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    Moderator bkmail's Avatar
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    When I would overload my old jetboat (115 Evinrude) or run very skinny water I would keep it WOT for a while. She still runs great w/no issues. DuPonts points make sense. I suppose if taken care of properly, use decent oil, and don't hit anything that would shock the system it should be OK.
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    Member Yukoner's Avatar
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    Quote Originally Posted by Blood_Vessel View Post
    I guess its how much fuel you want to burn and how loud you want it in your boat when your running... Next time out do some math if you drop down your RPM's and watch your speed on GPS you will find a sweet spot at some point your gonna just be making a lot of noise and burning a lot more fuel...
    Not counting those obvious drawbacks of course. Sometimes, you might have to run WOT for extended periods, say if you managed to get two moose and a pile of gear.
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    Moderator LuJon's Avatar
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    I am curious why any one would run floatbowls dry? I have tore down plenty of old bikes because the float was stuck down in a dry carb. I can't see where an outboard would be any different.

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    It's probably not necessary to run the carb dry if you aren't storing the motor for long (years).
    I'd agree with you, but then we'd both be wrong.

  11. #11

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    Quote Originally Posted by Yukoner View Post
    Not counting those obvious drawbacks of course. Sometimes, you might have to run WOT for extended periods, say if you managed to get two moose and a pile of gear.
    True but if you had two moose on board its worth it right to run WOT its not gonna destroy you motor, i'm pretty sure most newer outboards have rev limiters anyhow...

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    Moderator Paul H's Avatar
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    That's one of those it depends items. If the engine is properly propped, or has the correct size impellor and the boat isn't over loaded for the engine, then you can WOT for extended periods of time. Will you get the longest engine life running WOT all the time? No, for longest engine life run it at cruise rpm which is typically 2/3 or 3/4 of wot rpm. If you have to run WOT to get the boat to stay on step, then your engine is too small for your boat, and you will be rebuilding it or replacing it sooner than later.

    O/B's really are designed to run wot all the time w/o problems, but for best fuel economy and longest engine life, back off a bit.
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    Member tlingitwarrior's Avatar
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    Quote Originally Posted by LuJon View Post
    I am curious why any one would run floatbowls dry? I have tore down plenty of old bikes because the float was stuck down in a dry carb. I can't see where an outboard would be any different.
    Recommendation by guy who used to work on my outboard. Agreed prob not necessary if you run your motor quite often.
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    A mechanic I respected once told me, "80 percent of the wear and tear on a engine happens during the last 20 percent of the throttle". I think he was probably about spot on......

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    I did a little test recently. I usually run the boat at about 4400 and will cruise at 28 mph burning 10.4 gal/hr. I ran the rpms up to 4800 went 29.5 mph but was burning 12.5 gal/hr. As others said, the trick is to find the sweet spot that maximizes speed and fuel efficiency. Running that same engine WOT got me up to 35 mph but I was burning 15+ gal/hr.
    I'd agree with you, but then we'd both be wrong.

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    Member Yukoner's Avatar
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    Buddy of mine ran objs on the Copper river drainage for the Alaska Fish and Wildlife(?) dept. for a few years. Always carrying big loads of fuel, whatnot. Ran them HARD, all the time, and could never kill them (I think they ran pretty much all brands).
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    Member c6 batmobile's Avatar
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    Quote Originally Posted by Dupont Spinner View Post
    My belief and some personal experience that an engine that is running at a constant rpm many times with good maintenance will far out live one that cycles (shifting) thru the rpm range. Even running in the upper limits.

    My sleds run north of 8 grand and I get thousands of hours of use and they run variable but mostly closer to max rpm. Generators run at max rpms constantly for thousands of hours.

    One reason I believe this to be correct is you maintain constant combustion temperatures and it allows carbon to burn off and not accumulate.
    Same concept as highway mileage on a car vs stop and go mileage. While WOT may not be optimum its much better to keep the rpm constant when possible on any motor 2 or 4 stoke marine or otherwise.
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    I don't run them WOT. My jet motor (Tohatsu) blew up two TLDI air compressers from running WOT at WOT and that was in the first 150 hrs of opearation. I heard the USCG runs their SafeBoat Defenders with Honda 225s at WOT and they are getting 3,000 to 5,000 hrs on their motors. Last year I got a used 22' landing craft with a Honda 90 that will only plane out at WOT and it has a ton of hours on it (no idea) and I have to run it at WOT... and its been good. My 22' Hewes OceanPro (new) really only gets run at 80% power.

    Sobie2

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    Quote Originally Posted by AKBoater View Post
    I disagree that generators run at max RPM constantly. They might run at a constant RPM but not max. Next time you're around one find the little throttle and give it a push. the RPMs will go up.
    Portable gas generators are goverened at 3600 RPM, stationary diesel gen sets run at speed all the time, typically 1800 rpm, they are governed to not exceed. And they run for many many hours if serviced properly, but the RPM is low.

    Outboards with jets and even with props (assuming they are propped correctly) are running under a load, regardless of how much is in the boat.
    WOT will burn more fuel but I doubt it would shorten the life by a negligible amount. OB's turn at a relatively low RPM, considering what snow machines and motorcycles wil turn. Maintenance is key, and not much of that on a modern 2 S.
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    I empty my bowls every time I pull it out of the water - never a stuck float. Floats stick when you let the gas evaporate from the bowl leaving varnish.

    I don't like to run my old (1986 40hp zuki) WOT all the time. I do to pull up on step. I don't have a tach but that last little turn of the handle only gets me 2-3 mph with a fair amount of RPM gain. Last time coming back into Whittier I ran WOT for 18 miles - trying to hit the tunnel, wasn't concerned about fuel consumption at all. Didn't seem to bother her at all, but it makes sense that if you run anythign as hard as you can it will die quicker.

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