17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Optimizing the performance of Boston Whaler boats
azegarra43
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17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby azegarra43 » Mon Dec 21, 2020 1:55 pm

I have a 1998 17 Outrage II with a new Yamaha [that was later clarified to be an I-4 V MAX SHO 115]; it replaced a 1998 Yamaha 130-HP two-stroke-power-cycle engine. I chose the [Yamaha I-4 V MAX SHO 115] due to [concern about too much] transom weight. I wanted to stay within specification. Boston Whaler [gave a recommendation in some communication that] 420-lbs was the maximum [engine] weight.

[The Yamaha I-4 V MAX SHO 115 was later clarified to have a weight of 377-lbs.] [The weight of the old engine was not given but was later clarified to be 368-lbs.] [The] gear ratio [of an unidentified engine which was lated independently verified to be the new engine] is 2.15:1. The boat weight is 1700-lbs.

The [propeller under test] is a Solas TITAN stainless steel three bladed 13-1/4 x 17-pitch, used previously with the old engine.

PERFORMANCE DATA

Old Engine

The old 130-HP accelerated to 5,800-RPM and the boat speed was 41-MPH [with the propeller under test].

New Engine
The new F115 SHO accelerates to 6,000-RPM, and the boat speed is 37-MPH [with the propeller under test]. The new engine gets [the boat] on plane, but [the boat] just feels sluggish.

[One question posed four test conditions; the question has been rewritten into four separate questions--Moderator]

Q1: what would be the top boat speed if the propeller pitch were increased?

Q2: what would be the top boat speed if the propeller pitch were decreased?

Q3: how would acceleration from a standing start onto plane be affected if the propeller pitch were increased?

Q4: how would acceleration from a standing start onto plane be affected if the propeller pitch were decreased?

jimh
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Re: 17 OUTRAGE II 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby jimh » Mon Dec 21, 2020 3:40 pm

Q1: what would the top boat speed be if the propeller pitch were increased?

For the same propeller shaft rotation speed the boat will go faster.

Q2: what would the top boat speed be if the propeller pitch were decreased?

For the same propeller shaft rotation speed the boat will go slower.

What is unknown is how fast the engine will turn the propeller with different pitch than the test propeller.

Q3: how would acceleration from a standing start onto plane be affected if the propeller pitch were increased?

The effect depends on the amount of reserve power available from the engine. The only way to know the answer is to have the propeller power curve and the engine power curve. Generally, an increase in propeller pitch INCREASES the amount of power needed to turn the propeller. This will typically cause acceleration of the engine to be more difficult, and the engine will accelerate more slowly.

Q4: how would acceleration from a standing start onto plane be affected if the propeller pitch were decreased?

Generally reducing pitch decreases load, so less power is needed to turn the propeller. This typically results in the engine being able to accelerate more rapidly.

DATA NEEDED
We need to know the recommended full-throttle speed range from the manufacturer for the F115 SHO. If the maximum recommended full-throttle speed is 6,000-RPM or not much higher, and the F115 SHO is able to accelerate to 6,000-RPM under the load of the propeller under test, then the propeller under test is a good match for the engine and boat. Generally with four-stroke-power-cycle engines their maximum power output occurs in the very upper end of their engine speed operating range. This means that if you want to get all the horsepower you paid for, you must select a propeller that allows the engine to accelerate into the upper end of the its maximum operating speed range.

If you reveal to readers the maximum operating speed range for the F115 SHO engine, then more cogent comments can be made.

Also, if the manufacturer suggests there is an optimum engine speed range at full throttle, give that data, too. It often occurs that engine power output might really peak at a speed below the maximum allowed operating speed; this depends on the engine design.

You should also clarify which engine has which gear ratio, and give the weight of the old engine.

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Re: 17 OUTRAGE II 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby jimh » Mon Dec 21, 2020 3:52 pm

Regarding the comparison of old and new engine, I see that the top boat speed has been reduced to 37-MPH from 41-MPH. There are three likely causes for this:

  • the weight of the boat may have increased because the new engine may be heavier; increased weight always reduces maximum speed
  • it may be that the new engine uses a higher-numeric gear ratio that the old engine, and this results in the actual propeller shaft speed being slower at full-throttle with the new engine compared to the old engine
  • the new engine has less rated power than the old engine, 115-HP instead of 130-HP; decreased power always reduces boat speed

It is unlikely that by use of a different propeller you will be able to get the same speed with the new, perhaps heavier, less powerful engine than you did with the old, perhaps lighter, more powerful engine. Since you never revealed the weight of the old engine, readers cannot know if the new engine is heavier or lighter or the same weight as the old engine.

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Phil T
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Re: 17 OUTRAGE II 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby Phil T » Mon Dec 21, 2020 4:08 pm

Your new engine is labelled and marketed as the 115 SHO and not as the F115 SHO.
The 115 SHO is modified F115 engine with different cam shafts, reprogrammed ECU and a higher max WOT of 5300-6300 rpms. According to Yamaha, peak horsepower occurs at 5400-RPM

I do not recall Boston Whaler specifying transom weight ratings back in those days. It is a modern rating. The 1998 Outrage 17 has a maximum horsepower rating of 150-HP. We use the typical weight rating of a 150 2-stroke available at the time is a weight guide, thus around 400-lbs.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

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Phil T
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Re: 17 OUTRAGE II I-4 V MAX SHO 115

Postby Phil T » Mon Dec 21, 2020 4:37 pm

It is a general recommendation to delay performance testing until after the manufacturer's break-in has been completed. Changes based on preliminary testing results will lead to incorrect recommendations for props.

You have reduced the horsepower and gained engine weight with the new engine. A reduction in boat speed is expected.

Based on my experience, your target speed,when rigged and propped right, would be 39-40 mph when running light and solo.

Prop design is unique across models and brands. Predicting changes in pitch would only apply if you stay with the same make and model of prop.

Size is not universal so changing brand/model will not result in identical performance. A 13-1/4x17" Solas Titan will not necessarily perform the same as a 13-1/4x17" Yamaha Performance Series.

A1: If you increase pitch, engine speed will fall. Speed change depends on prop model.

A2: If you decrease pitch, engine speed will rise. Speed change depends on prop model.

A3: Depends on prop make/model

A4: Depends on prop make/model

When I ran your engine specifications into a prop selection tool [WOT of 6300, gear ratio 2.10, slip of 5%, target speed of 39], it returned 16" of pitch. I suggest a Yamaha painted stainless steel prop in 16". Solas props are not used heavily by Whaler owners.

I would also note you do not indicate engine mounting height. It is recommended the engine anti-cavitation plate be 1-2" above the keel of the boat. If the holes follow the BIA standard measurement, this would be 2-3 holes up (top bolt 3rd down from top).
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

azegarra43
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Re: 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby azegarra43 » Mon Dec 21, 2020 4:47 pm

[The new engine model designation] is the VF115 SHO [but Yamaha refers to it as a VF115LA--Moderator]. I just finished the break-in period. [In the future] I will be performing [the factory specified] 20-hour-service; currently [the new engine has] 13 hours [running time].

The previous 130-HP two-stroke-power-cycle engine weight was 368-lbs. The new [Yamaha I-4 V MAX SHO® 115] engine weight is 377-lbs, just slightly heavier [by 9-lbs].

I will do some testing [in the future]. Then I will post the information needed for [maximum engine speed] and [maximum boat speed] with a full [fuel] tank and with the same buddy aboard [as when] I took [the performance data for the old engine].

[For a source for the maximum] transom weight, I called Boston Whaler and got their advice.

I'll be back. Thanks for the quick response. I love this this forum.

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Re: 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby jimh » Mon Dec 21, 2020 7:16 pm

Moderator's note: I revised earlier posts to include the clarification on the exact engine model and the exact engine weight of the "new" and "old" engines.

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Re: 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby jimh » Tue Dec 22, 2020 10:30 am

PHIL--thank you, as always, for digging up essential information that was not provided by the OP regarding the engine speed ranges and the precise model of engine.

From the Yamaha web page I found these specifications:

Prop Shaft Horsepower 115hp at 5500 rpm
Full Throttle RPM Range 5300 ~ 6300


The designated engine speed of 5,500-RPM as providing 115-HP at the propeller shaft is certainly a valid statement, but unclear is whether or not the engine can produce more than 115-HP at higher engine speeds.

As PHIL points out, testing may be better if delayed until the break-in period is over. If may be possible that after break-in the engine might accelerate to even more than 6,000-RPM with the 17-pitch propeller already on hand and tested. The added engine speed should add some more boat speed.

Regarding going to a propeller with more than 17-pitch: that might not be the best option in consideration of the comment that the boat already feels sluggish in handling and accelerating with a 17-pitch propeller. I interpret "sluggish" as meaning the boat takes longer time than expected to accelerate in boat speed and the engine is perhaps struggling to push the boat onto plane. If that is the situation with the 17-pitch, then increasing to 19-pitch would be likely only to make those characteristics worse, not better.

Again, the new engine is rated for lower power output than the old engine, so one cannot expect that the performance will be identical. However the marketing terms "V-Max" suggests maximum velocity or speed, and and "SHO" suggests special high output version. Both those marketing terms suggest that perhaps the engine makes more than its rated 115-HP.

Regarding the now clarified weights of the old engine (368-lbs) and new engine (377-lbs), the 9-lbs difference is not particularly significant. Since the boat weight is at least 2,100-lbs, a change in boat weight of 9-lbs is only a change by a factor of 2109/2100 or 0.4-percent. The effect of boat speed of such a small change is going to be about 0.2-percent. At a speed range of 40-MPH that is less than one-tenth a mile-per-hour influence. There is no way to measure that because boat speed is generally only known to an accuracy of about 0.5-MPH.

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Re: 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby jimh » Tue Dec 22, 2020 10:41 am

Re the model designator for this engine: I don't see the suggested model designator "VF115 SHO" listed by Yamaha.

In a performance report for an In-line I-4 Vmax 115 SHO engine, the model designator used is VF115LA

https://yamahaoutboards.com/CMSPages/Ge ... 1f690bd76f

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Re: 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby jimh » Tue Dec 22, 2020 11:02 am

Re predicted performance with a propeller pitch of 16-inches: using a propeller calculation with values

RPM = 6300
RATIO = 2.15
PITCH = 16
SLIP = 10 (percent)

the speed of advance calculates to 40-MPH.

PHIL's suggestion to try a 16-pitch is a very reasonable and likely useful test.

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Re: 17 OUTRAGE II Yamaha I-4 V MAX SHO® 115

Postby biggiefl » Tue Dec 22, 2020 12:14 pm

My 19 REVENGE weighed about the same [as a 17 OUTRAGE II]. With a 115 Suzuki the top boat speed was 40-MPH. I would assume [a 17 OUTRAGE II with a Yamaha I-4 VMAX SHO 115] should [have boat speeds of 40-MPH] as well.

A friend had a 1995 17 Outrage with a 150-HP Johnson, and that boat did close to 50-MPH.

I am not sure why the top speed [for a 17 OUTRAGE II] with a 130-HP would only be 41-MPH.

Also, I would NOT test with a full fuel tank and two people aboard.

I would test solo with less than a half-full tank of fuel.

Is the engine trimmed out all the way?

How high is the engine mounted?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).