posted 12-16-2013 08:25 PM ET (US)     

I want a lightweight main engine which will troll pleasantly as I don't care for my boat's handling when I add a kicker. I'm focused on the DF140 for its light weight, cost, and no oil tank in the splash well.

My boat sees frequent general boating use on the lake, loaded with two to four adults, less than half-full tank of fuel, and a few cold drinks. We only occasionally tow water toys. I would estimate typical 500 to 800-lbs loads, including fuel.

The 18 also sees a couple of West Coast salmon fishing trips per year, where we'll head out full of fuel, two to four people, plus downriggers and overnight gear. For these trips, my typical loaded weight can be as high as 1,200-lbs, including fuel.

I'm curious as to what the propeller experts might think of going with a DF140, and two propellers to swap between?

As most of our use is lightly loaded on the lake, where we can use a bit of speed, I'm thinking this engine would be enough to get us into the 42 to 43-MPH WOT range, even though I have found 40-MPH to be fast enough.

When we go fishing, we could "gear down" with a lesser pitch propeller so we can still reach maximum RPM and keep the performance up, but sacrificing some top speed which we couldn't use out there anyway.

posted 12-17-2013 06:53 AM ET (US)            

http://continuouswave.com/cgi-bin/crouchcalc.pl

My first calculation is to assess the present performance data:

Speed = 45-MPH
Power = 150-HP

Using the general hull factor constant of 180, the calculator calculates the total weight of the boat to be 2,400-lbs. Next, I decrease power to 140-HP to represent the new engine. The speed recalculates to 43.5-MPH. Finally, I add 400-lbs to the calculated weight to account for the condition of heavy loading mentioned (1,200-lbs) compared to the typical load (800-lbs). The final speed estimate is now 40.2-MPH.

With these estimates, the 140-HP engine would have a top speed of 43.5-MPH with typical load and 40.2-MPH with the heavy load.

My remarks now will be based on calculations made with my "Propeller Calculator" tool, available to all and often used by "experts" at

http://continuouswave.com/cgi-bin/propcalc.pl

The inputs to the calculator will be

ENGINE SPEED = 5,600 to 6,200-RPM
ENGINE RATIO = 2.59:1

as listed at http://www.suzukimarine.com/Product%20Lines/Outboard%20Motors/Products/ DF140/2012/DF140A.aspx

BOAT SPEED = 43.5 (as calculated above)

PROPELLER SLIP = 10 % (based on typical propeller performance)

Now we calculate the propeller pitch for the two extremes of the engine wide-open throttle (WOT) speed range:

Using the maximum WOT of 6,200-RPM, the PITCH calculates to 21.3
Using the minimum WOT of 5,600-RPM, the PITCH calculates to 23.6

Next we reduce the target speed to 40.2-MPH, as estimated to be our speed potential with the heavy load, and recalculate the propeller pitch for the two engine speeds:

Using the maximum WOT of 6,200-RPM, the PITCH calculates to 19.7
Using the minimum WOT of 5,600-RPM, the PITCH calculates to 21.8

posted 03-08-2014 01:19 PM ET (US)         

From searching, I see the most common suggestions for the 2.59 gear ratio DF140 on an Outrage 18 are the SS Suzuki 14x20 or the Stiletto Advantage 14x20. I've also seen mention that these two props are very similar.

Another member is very happy using a 18p Powertech 4-blade on the earlier DF140 with the 2.38 gear ratio, for offshore use.

posted 03-18-2014 09:28 AM ET (US)            

I have a DF140, and I'm running a 14 x 22 prop. I'm a tad over propped and top out at 5900 rpm and 42 mph. I've got lots of old bottom paint and my engine is mounted a hole low.

I also make a yearly trip with loads at least as heavy as you're describing, and the first year I had that outboard, I brought a second prop with less pitch. Never needed it. The boat jumps up on a plane without hesitation.

I'll bet if you put a 14 x 20 on there, you'll be good to go in any situation.