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Thread: Cruising RPM with Outboard

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    Member hoose35's Avatar
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    Default Cruising RPM with Outboard

    I am new to using a 4 stroke outboard for power, I have been using inboards. My question is, what kind of RPM do you guys cruise with? What is a safe range for an outboard? I have a Yamaha F150. With my inboards, I always cruised between 3000-3400 rpm, but had heard of guys in the 4000 range, I would rather cruise on the low side to save fuel and wear and tear on the engine.
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    Member AKluvr95's Avatar
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    I'm curious too...the previous owner said there's something in the owners manual but I didn't see anything specific. We also have a single Yamaha 150 [Weldcraft Ocean King 240 Ext Alaska Bulkhead] and while I can't recall the exact RPM [because it has been a while] but MPH ground speed as indicated on my GPS is right around 28. This is where the previous owner said he ran it and she seems to perform well.

    Quote Originally Posted by hoose35 View Post
    I am new to using a 4 stroke outboard for power, I have been using inboards. My question is, what kind of RPM do you guys cruise with? What is a safe range for an outboard? I have a Yamaha F150. With my inboards, I always cruised between 3000-3400 rpm, but had heard of guys in the 4000 range, I would rather cruise on the low side to save fuel and wear and tear on the engine.

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    Moderator Paul H's Avatar
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    Assuming a prop, it depends on how you are propped but with a redline of 6000 rpm, most outboards perform best with a cruise in the 4000-4400 rpm range. If you want top fuel economy, get a floscan or such and see what is the most efficient for your engine and prop. Cruising on the low side can burn more fuel, so you really need to compare fuel burn to speed to know what is most efficient for your engine. The real key to keeping the wear and tear down is properly propping your engine. If you can't hit redline or within a couple hundred rpm of redline with your prop, it's got too much pitch and is putting more strain on your engine.

    With my suzuki 140 one prop performs best at 4000 rpm, the current prop at 4400 rpm, my engine redlines at 6500 rpm. When I'm fishing with buddies and splitting fuel costs, conditions permitting I'll be running it at 5000-5500 rpm as running faster on long day trips can allow an extra 1/2 hour fishing, or maybe make the difference between hitting a Whittier tunnel openin or waiting another hour.
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    Member hoose35's Avatar
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    Thank Paul, the boat will hit 5600rpm, I think I will be looking at a different prop because I know I will be loading it heavier at times than I did when it hit 5600. Also, at 4000 rpm, it goes plenty fast enough, so I will probably keep it in that range, but after I get my fuel flow rigged up, I will get it dialed in from there.
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    Moderator Paul H's Avatar
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    Dropping 2" of pitch should bring you up 400 rpm and hence right at the redline.
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    Member hoose35's Avatar
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    How about if I wanted to go to a 4 blade prop, I have heard that have better torque, but you loose top end speed, which is fine with me?
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    Member Alaskanmutt's Avatar
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    I lost around 5 mph but gained 4 gph when I went to a lower pitch, larger diameter 4 bladed prop. But the main reason I swapped was the 3 bladed prop was taking 100 yards to get on step, the 4 blade jumps on step like a scalded cat.
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  8. #8

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    I run a F150. 4-4200k is where you want to be, if you're propped out right. Get around 4400 and you'll start using gas. If you discipline yourself, that motor should last you forever if you stay at 4k, and do your 100hrs religiously. I know some commercial guys who troll all summer with their F150s. They have an insane amount of hours on them. I'm barely to 500 on mine, probably hit 1000 by the end of the summer.

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    Member Akgramps's Avatar
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    Over proping is hard on motors and generates heat and premature failures, the theory of hitting max rpm at WOT to be propped right is a misnomer, every engine has a "WOT operating range". I think the 150's is 5000 to 6000 RPM's, check your owmers manual.
    According to Yamaha:
    "A properly sized prop should allow the motor to reach the middle or upper 1/2 of that operating range when at WOT". So, for the 150, you should see 5500 PRM or higher at WOT. These are relatively light boats with high HP, if you are proped right for 90 percent of the time and run heavy once in while and are slightly overproped I doubt it would cause any lasting ill effects. If however you run heavy all the time and cant achieve the operating range, its time to reprop......

    I know this is about props, but.......Interestingly most OB's with a jet never see rpms that high, usually a well set up jet will run 5200 -5400 prm, at least on the boats I have owned.........so the jet pump must not put the same load on a motor that a prop does.
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