1976 OUTRAGE 19 Re-power

[epj]

Q1: between a SUZUKI 140-HP and a SUZUKI 150-HP, [which is the best match for a 1976 OUTRAGE 19 boat]?

BACKSTORY
Since 2010 my 1976 OUTRAGE 19 has been powered by a 1999 Johnson 130-HP 25-inch-shaft engine mounted on a 4-inch CMC manual jack plate. The engine weighed 378-lbs.

I may buy a SUZUKI 140-HP (410-lbs) engine or a SUZUKI 150-HP (510-lbs) engine. The dealer stated “ the 150 swings a considerably larger propeller, has considerably more torque, and would increase the boat speed at full throttle by 8-MPH.

In choosing between the 140-HP and the 150-HP my focus is on the best match [to the 1976 OUTRAGE 19 boat].

[jimh]

The dealer stated “the 150 swings a considerably larger propeller, has considerably more torque, and would increase the boat speed at full throttle by 8-MPH [compared to the 140-HP engine]

Any increase in power is offset by the increase in weight. Boat speed increase only with the power-to-weight ratio to the 0.5 exponent.

An increase to 150 from 140 will only increase the speed by a ratio of 1.035—and that is disregarding the extra weight.

If your top boat speed were 35-MPH with the 140, the boat speed with 150 would only increase to 36-MPH.

[Phil T]

The DF140a is highly recommended by Whaler owners.

This engine has a lower weight which is preferable when repowering a classic model.

Don't get suckered by the dealer. He's looking for a more expensive sale.

[epj]

Jim and Phil, thanks very much. If I make the move, I will go with the 140 Suzuki.

[Blackduck]

I have owned [a c.1976 OUTRAGE 19] powered with the Suzuki 140. Do yourself a favor and listen to your dealer and go for the 150. The boat can use the additional weight in the rear. The boat will be bow heavy with the [140] engine.

The [140] engine is also shy of the claimed 140-HP. Top [boat speed] will be less than 40-MPH. A good 140-HP engine should push that boat to 44-MPH. [The 140 is] otherwise a good engine.

Get what works best with your boat.

This is a classic era Boston Whaler boat that can benefit from a heavy but powerful engine.

[jimh]

The [140] engine is also shy of the claimed 140-HP. Top [boat speed] will be less than 40-MPH. A good 140-HP engine should push that boat to 44-MPH.

Assuming the reported speeds are correct, we can then estimate the power of the Suzuki DF140 as something less than 140-HP based on its ability to only push the boat to less than 40-MPH while a real 140-HP engine would must the boat to 44-MPH.

For this analysis I will assume that a speed of "less than 40-MPH" would be 39-MPH. If the "140" engine only produces 39-MPH while the "real 140-HP" engine produces 44-MPH, the inference is then that the horsepower of the "140" must be (assuming again no change in total weight) only 110-HP.

This is a preposterous situation as follows:

--the "140" engine power rating should be clearly indicated on its EPA or EU certification data, and could not possibly be only 110-HP while carrying a 140-HP rating;

--the SUZUKI DF140a engine is actually the best selling SUZUKI engine (by some older reports of sales volumes from Suzuki themselves which indicated it was their "most popular" model), and the suggestion that boaters would repeatedly purchase and endorse this engine that produces only 110-HP instead of its rated 140-HP seems very unusual, as such a significant lack of powered compared to the rated power would immediately become the talk of every boating forum.

Also, if the claim of "top boat speed will be less than 40-MPH" is to be interpreted as 38-MPH, then the "140" would be producing only 104-HP.

In any assessment of the maximum boat speed possible with a particular boat and engine combination, the rigging of the engine and selection of the propeller must be done in a manner that permits the engine to accelerate into an engine speed where it can produce its rated power output. Poor propeller selection can result in any engine not being able to accelerate under load to an engine speed at which it is capable of producing its rated power output. Such poor rigging is not the fault of the engine or its manufacturer.

[kladd]

I find myself doing my own analysis/comparison of the Suzuki df140 and df150/175 for my own repower. Suzuki seems to have an excellent reputation. I have never owned or operated either of these motors so there's that.

Consider that the df140 is a 125 cubic inch motor. It is a souped up version of the df90/115. One trick used to get the 140hp rating was to increase the rpm range, albeit slightly. Another was to increase displacement from 119 to 125ci. The df140 at 410lbs is a marketing miracle.

The 150/175 is a 175 cubic inch motor. So the df175 is achieving 1hp/cubic inch.

If displacement were the ONLY factor, and the df175 is properly rated, then the df140 should achieve 125hp based on its 125 cubic inches. Pretty simple math!

Of course there's more to this but I consider the df140 and df150 to be VERY different motors from what the numbers "140'" and "150" would seem to represent. For many applications the weight advantage of the df140 is compelling.

Not so for my '71 21' Outrage. Previous motor was Yamaha 150 2 stroke which performed well so df150 or even df175 is a no brainer for me.

[Masbama]

[Reports he has a SUZUKI DF140 engine] on a 2003 190 Nantucket, which has a T-Top--adding weight and drag. With my family of four [onboard, the 190 NANTUCKET with the DF140 engine can accelerate to a boat speed of just] over 40-MPH. We enjoy tubing and knee boarding, and we have no problem doing with this set-up.

I would say [the SUZUKI DF140 engine] for our hull as it is set up is “just enough.” It does the job for us. A 150-HP would be nice but it would add more weight. Also, I’m not the type to cruise around over 30-MPH.

[Moderator's note: originally in the above comment there was an allusion to an earlier post but no link was provided. The earlier post that was being alluded to shows the emission label of a 2015 DF140a engine with a power rating of 103.0 kW. Converting that to horsepower gives 138-HP. For more details, see

Dock Talk on Suzuki DF140
https://continuouswave.com/forum/viewto ... 71&p=39025 ]

[jimh]

The above linked thread where Blackduck gives his anecdotal observations about the DF140 engine is actually quite strange, as it contains the admission of participant "Blackduck" that he joins any discussion about the DF140 engine to report how little actual horsepower he thinks it makes. The campaign by "Blackduck" to present his negative opinion of the Suzuki DF140a engine continues here in this thread. Sorry, but the emission sticker indicates 103.0-kW which is 138-HP, and that is in close agreement with the cowling decal that declares 140-HP.

FOUR-STROKE-POWER-CYCLE ENGINES
Many four-stoke-power-cycle outboard engines have a curve of power output as a function of engine speed that requires the engine to be able to accelerate to the maximum permitted engine speed in order to reach the specified maximum power output. This requires that the rigging of the engine on a particular boat be done with a propeller that properly permits the engine to accelerate to its maximum rated engine speed in order to get the maximum rated power output. Selecting the propeller becomes very important. This behavior is not unique to the Suzuki DF140a engine, as you can see in the graph below in Figure 1 where the power output as a function of engine speed for several four-stroke-power-cycle engines is plotted:


Fig. 1. A plot of engine power output as a function of engine speed for several engines from published sources.

As shown in Figure 1, an engine with a broad power band such as the E-TEC 150-HP engine begins to produce it rated 150-HP at engine speeds as low as 3,750-RPM and continues to exceed 150-HP from that engine speed up to 6,000-RPM. The four-stroke-power-cycle 150-HP Yamaha and Honda engines only reach their peak power at their maximum allowed engine speed, 6,000-RPM.

Any engine whose ability to produce its rated power is limited to a small range of engine speeds will tend to need a carefully selected propeller for each load condition. For example, if a boat is normally operated with only one person aboard, and the propeller is selected for that load, when the boat is loaded with five people there is a good chance that the engine will not be able to accelerate into the narrow range of engine speed at or near the maximum permitted engine speed that is needed to develop its rated power. But that does not mean the engine is never capable of producing its rated power, it means that the engine is more sensitive to operating with unusually heavy loads compared to the normal load for which the propeller was sized.

There are two general methods for improving the width of the engine speed range at which an engine can develop its rated power: use forced induction, or use larger displacement. Mercury Marine demonstrated quite successfully that using forced-induction (supercharging) was a method to permit smaller displacement engines to develop their rated horsepower over a wider range of engine speeds. But Mercury Marine eventually adopted the larger-displacement approach to getting their four-stroke-power-cycle engines to be able to improve the range of engine speeds at which they can create their rated horsepower. From a manufacturing perspective, larger displacement costs less to manufacture than exotic superchargers, which also explains the change in strategy from Mercury Marine.

Of course, "Blackduck" is quite free to continue his campaign against the Suzuki DF140, but in a similar manner I will continue my rebuttle whenever he starts up again.