1999 OUTRAGE 21 with 150-HP

Optimizing the performance of Boston Whaler boats
Whal
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1999 OUTRAGE 21 with 150-HP

Postby Whal » Tue Apr 07, 2020 7:17 pm

My friend has a 1999 Outrage 21 re-powered with 2019 Suzuki 150-HP engine. The engine is mounted one-hole-up, and the propeller is a Suzuki three-blade 15 x 21-pitch (part number 990C0-00830-21P).

The top boat speed is 30-MPH when the engine accelerates to 5,000-RPM at full-throttle. The maximum RPM range for the Suzuki DF150 is 5,000 to 6,000-RPM. My friend says the DF150 is laboring, time-to-plan is long, and fuel economy in MPG is terrible.

I think the 1999 Outrage 21 is a lot of boat for a 150-HP engine.

Give some suggestions [about propeller or engine mounting height] to improve performance. Thanks--Al

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Phil T
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Re: Correct Propeller and mounting height

Postby Phil T » Tue Apr 07, 2020 9:53 pm

Wow, 150-HP is not a lot of power for a 2,500-lbs hull. The minimum recommended power for the 1999 OUTRAGE 21 is 135-HP.

I would change to a propeller with less diameter and less pitch to spin up the engine to 6,000-RPM.

With a gear ratio of 2.5:1 , engine speed of 6,000-RPM and a target boat speed of 35-MPH, the prop calculator shows 16-pitch

propsheet__.jpg
Fig. 1. Chart of Suzuki Stainless Steel propellers.
propsheet__.jpg (20.44 KiB) Viewed 1737 times
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1992 Outrage 17, 1992 Evinrude 115

jimh
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Re: 1999 OUTRAGE 21 with 150-HP

Postby jimh » Wed Apr 08, 2020 7:37 am

Clearly 21-pitch is too much propeller load for the boat-engine combination.

Generally most four-stroke-power-cycle outboard engines develop their rated horsepower near the peak of their maximum RPM range. The 21-pitch propeller load is limiting the engine to only the very bottom of the recommended engine speed range.

To improve acceleration of the boat to plane and to allow the engine to accelerate into the upper end of its full-throttle range, reduce propeller pitch. A rough rule of thumb is a 2-inch reduction in pitch will cause about 400-RPM increase in engine speed. Dropping to 17-pitch from 21-pitch is likely to improve boat acceleration onto plane and should let the engine accelerate to close to 6,000-RPM at full-throttle. At 6,000-RPM or close to it, the engine will be able to produce its full-power 150-HP output.

A good dealer selling an engine for re-power should also make the proper propeller selection. If your friend bought the 21-pitch propeller as part of a package along with buying the new engine, your friend should go back to the dealer who sold him the engine and complain about the poor performance. Tell the dealer you want him to take back the 21-pitch and give full credit. Then ask the dealer to loan a 17-pitch for a sea trial. If the 17-pitch works better, your friend will buy it. If the dealer won't cooperate, your friend should sell the 21-pitch for whatever he can get for it, and find another dealer who will work with him on getting the right propeller.

Also, is the engine we are discussing the newer model DF150A or the older DF150?

Regarding anticipated top speed,
Estimation of top speed for a moderate speed planing hull is based on boat weight, hull design, and engine power. Using the method developed by naval architect George Crouch, with the follow parameters:

    Boat weight = 4,000-lbs boat (which is what a 2,500-lbs hull might weigh with engine, fuel, gear, and crew)
    Hull constant = 180 (a reasonable value for a Boston Whaler V-hull)
    Power = 150-HP

the method predicts the top boat speed for a moderate planing hull to be 35-MPH.

Find a propeller pitch from engine speed and gear ratio
Using 35-MPH as a target boat speed, and these values for input

    RPM = 6000
    RATIO = 2.5
    SLIP = 0.1 (10-percent, a typical value for a real-world propeller)
    MPH = 35

the calculated propeller pitch is exactly 17-inch.

If you friend wants to stay with a Suzuki propeller, he should try the 17-pitch 990C0-00830-17P.

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Re: 1999 OUTRAGE 21 with 150-HP

Postby jimh » Wed Apr 08, 2020 8:44 am

Regarding engine mounting height:

Until the propeller pitch is more appropriate, your friend should not worry about engine mounting height.

With your friend's engine now at one-hole-up your friend is at a good starting point. Your friend needs to get the 17-pitch propeller on and make a very simple initial test: find out what speed the engine can accelerate to with the 17-pitch. If the engine spins up to more than 5,700-RPM, then the 17-pitch is probably the right propeller.

Your friend should not change the engine mounting height until he has run the boat extensively with the new propeller, and has developed good data about boat speed, engine speed, and fuel economy.

Also, how does your friend gather data about boat speed, engine speed, and fuel economy? You cannot really make small adjustments unless you have really good data measurement methods. And when adjustments are made, you have to re-test in the same conditions as the baseline data was obtained, such as sea state, weather, wind, current, boat weight, fuel load, and so on.

If after your friend has gathered some data with the new propeller and after observing visually the relationship between the flow of water around the gear case and the engine anti-ventilation plate when the engine is properly trimmed and the boat is on a fast plane, and after operating the boat in a variety of sea states, including going into head seas at a slow planing speed, and if your friend is still not happy with the boat performance, he could experiment with engine mounting height changes.

Your friend should consider that straight-line top boat speed in calm and protected water may not be the best target for optimization of engine mounting height, unless those conditions are the conditions your friend will always be operating his boat in.

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Re: 1999 OUTRAGE 21 with 150-HP

Postby biggiefl » Wed Apr 08, 2020 10:15 am

I agree with Jim on most of his points.

Suzuki engines like to be mounted high. Why the dealer--if it was the dealer--only mounted the engine one hole up is puzzling. I would mount the engine [threr-holes-up] if not all the way up [four-holes-up]. Many Suzuki four-stroke engines have five mounting holes. I also agree on the 17P prop, 21 is for a much higher speed.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Whal
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Re: 1999 OUTRAGE 21 with 150-HP

Postby Whal » Wed Apr 08, 2020 10:32 am

Thank you to everyone for all the detailed information,I will forward it to my friend. Continuous Wave is a great resource to Whaler owners and is monitored by a great bunch of knowledgeable people. Thanks again to all who responded. Al

Jerry b
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Re: 1999 OUTRAGE 21 with 150-HP

Postby Jerry b » Sat Apr 11, 2020 7:01 am

I’m "the friend" in the prior discussions.

The dealer [who sold the Suzuki 150-HP engine] is a small shop, close to home. The dealer used the Suzuki performance chart when he ordered the propeller.

I did go back to the dealer with my problems. The dealer said he couldn’t exchange the propeller but would sell me one at cost ($400).

I have a 15-pitch steel propeller I used on an old Yamaha 200-HP two-stroke-power-cycle. It may work on the Suzuki 150 Suzuki.

If [the old steel 15-pitch propeller] does fit, I think it is worth a try--as long I don’t [let the engine accelerate to more than] 6000-RPM.

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Re: 1999 OUTRAGE 21 with 150-HP

Postby jimh » Sat Apr 11, 2020 8:08 am

After your sea trial with the 15-pitch propeller, report the performance data. Report the engine speed (in RPM) and boat speed (in MPH) for engine speed ranges that put the boat on plane. More advice can be offered after you post this data.

Also report how you measured engine and boat speed. Also report the environmental conditions and any characteristics of the boat's weight, such as volume of fuel, number of passengers, amount of gear aboard.

I suspect the 15-pitch propeller will allow the engine to accelerate much faster. You are wise to keep engine speed in the recommended range.

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Re: 1999 OUTRAGE 21 with 150-HP

Postby Jerry b » Sat Apr 11, 2020 9:06 am

Will do when I get my boat to water. Thanks for your input.

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Re: 1999 OUTRAGE 21 with 150-HP

Postby biggiefl » Mon Apr 13, 2020 11:49 am

Jerry, your dealer is ripping you off. No way is cost $400. Shop around and see what you can find but try the 15" first. Are you sure it is a 15" prop in pitch and not a 15x17? Reason I ask is if you had that 200 on your current boat, it would not be using a 15" pitch, more like a 17 or 19 depending on load. If it is a prop that you can change the hub it will fit. If it has splines and a rubber hub, it is probably not compatible with your new engine. Usually Suzuki uses the old OMC prop hubs and Yamaha uses Mercury.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Jerry b
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Re: 1999 OUTRAGE 21 with 150-HP

Postby Jerry b » Sat Jan 23, 2021 2:32 pm

I tried the Yahama 15 1/4 x15-m and it worked better than the 21 pitch Suzuki prop top speed with 100 gal in main tank and 12 gal in 20 hp 4 stroke tank and 3 adults and loader with fishing gear 10 trolling rods and tackle.top speed 28 mph on a flat day on Lake Erie and 5900 rpms on tach had to be careful not to over rev .Reached plane much quicker.am going to buy a 17 pitch 15 1/2 Suzuki prop any suggestions on the best price and quality ss prop would be helpful and will sell one hardly used 15 x21 Suzuki prop10 hours used .Jerry B

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Phil T
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Re: 1999 OUTRAGE 21 with 150-HP

Postby Phil T » Sat Jan 23, 2021 3:15 pm

Jerry -

Note that propeller performance is not connected to size due to different blade design for each model of prop.

A 15-1/2 x 17 Yamaha painted stainless steel prop will not necessarily perform as a 15-1/2 x 17 Suzuki stainless steel.

It is important to note make and the model and size of each propellor.

With prices ranging from $250-$800 for a prop and dealers not accepting returns, it is appropriate to get it as close to correct as possible.

I recall that Ken Reeves @ Prop Gods allows props purchased from him to be traded back in for a $35 fee. He is quite knowledgeable with Boston Whalers and carries several very good lines of props. You may want to contact him. http://www.propgods.com
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Jerry b
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Re: 1999 OUTRAGE 21 with 150-HP

Postby Jerry b » Sun Jan 24, 2021 9:58 am

Phil T thanks for the information will check it out

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Re: 1999 OUTRAGE 21 with 150-HP

Postby biggiefl » Mon Jan 25, 2021 12:04 pm

3 adults, 900lbs of fuel, 20hp kicker, and gear is a lot to ask from a 150hp. I would assume though that it should do better than 28mph with the right prop, especially when you have to be careful not to over rev. As I mentioned before, Suzukis like to be raised high but you can not do that until you get closer with prop choice.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).