Re: OUTRAGE 18 with Yamaha 150-HP

Optimizing the performance of Boston Whaler boats
jimh
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Re: OUTRAGE 18 with Yamaha 150-HP

Postby jimh » Tue Oct 23, 2018 10:47 am

This is a disjointed thread that was originally in reply to three separate threads posted in three separate forums by the same participant, and all threads were seeking advice about re-powering an OUTRAGE 18 that had twin 70-HP engines. The original poster deleted all his posts. The several replies contain good information and the thread is being retained to preserve that good information.

The initial post sought advice regarding twin engine re-powering:

Jetfishin wrote:...Why twins? Never had a boat with twins.


For about five years I owned a pair of 1987 Yamaha 70-HP 850-cc three-cylinder classic two-stroke engines on a 20-foot Boston Whaler hull. They were nice engines, and I believe they are still on that boat and still running well with the new owner who bought it from me about ten years (or longer) ago. Setting up an OUTRAGE 18 with those twin 70-HP engine was usually seen in ocean coastal areas, like Key West where you are.

My newer (and larger boat) has a single engine, and I don't miss the twin engines. They always needed attention to get them to run at the same RPM, so you end up playing with the throttle handles all the time you were underway on plane.

As for twin modern engines on an OUTRAGE 18, that has been done, and most notably by Dave B with the famous GAMBLER. GAMBLER had twin E-TEC 90-HP engines. It was really a great boat, and Dave ran it all over the place in big water--big freshwater like Lake Superior, Lake Nipigon (a real wilderness lake with almost no inhabitation), Lake Huron, Lake MIchigan, and it was a wonderful boat. But guess what happened when he wanted to sell it: no one wanted to buy it because there was too much money in the very new modern twin engines. It was actually rather sad, but to get his investment out of the GAMBLER, Dave had to dismantle the boat and sell off the pieces. And I mean the pieces. The engines went first, to separate buyers as I recall. Then the hull and all accessories were parted out, until only a bare hull remained. I mention this because it was a lesson in investing big money into new engines for 30-year-old boats. You may not be able to recover that investment if you decide to sell. There just are not that many buyers out there for an 18-footer with modern twin engines on the transom that cost $20,000 or more.

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Re: OUTRAGE 18 with Yamaha 150-HP

Postby jimh » Wed Oct 24, 2018 12:40 pm

Originally in reply to a question about performance of an OUTRAGE 18 with 150-HP Yamaha:

Jetfishin wrote:Q1: How will the Yamaha act?


Those older Yamaha classic two-stroke-power-cycle engines are generally very good engines. If the price is attractive and the engine's condition is as nice as you described, then it would be a great engine for an OUTRAGE 18.

Several years ago I drove an OUTRAGE 18 with a Yamaha 135-HP V6, and it was like driving a sports car: very responsive.

If you don't run the engine for hundreds of hours every year, the fuel economy of a classic carburetor two-stroke engine won't be so bad that it will be a cost factor.

Also, you can probably sell those twin Evinrude 70-HP engines as either a working engine or a parts-engine, and recover some value for them.

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Re: Re-power OUTRAGE 18 on a Budget

Postby jimh » Wed Oct 24, 2018 3:43 pm

Originally in reply to a question about engine mounting height:

In general, mounting an engine one-hole-up is a good height to start any trials.

Try a three-blade 17-pitch propeller. Yamaha made a line of steel propellers that seem to work well with their engines. They are often painted black but are steel, not aluminum.

PHIL should be able to help you more than I can.

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Phil T
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Re: Re-power OUTRAGE 18 on a Budget

Postby Phil T » Thu Oct 25, 2018 9:47 am

For prop suggestions, we want to know size but also make and model too since prop size/performance is not universal.

From very long archived thread, here is the salient information :

Note information is from 2013 so prices are not accurate. The Stilleto Advantage is no longer available,

do not recommend an aluminum propeller. It is a myth that an aluminum propeller will offer you some sort of protection in the event of a propeller strike.
That said, if you do stick with aluminum, I'd just use the 14" x 19" Yamaha aluminum three blade, part #6G5-45945-01-98

If you want a good stainless steel prop I'd use the 14-1/4" x 18" Yamaha Performance Series 3-Blade, part #MAR-GYT3B-V6-18

The Yamaha Performance Series 3-Blade is the same propeller as the Stiletto Advantage and the Turbo 1, but offered in even pitches.

The Yamaha Performance Series 3-Blade can be had for as little as $475 but if you buy the Stiletto branded version of this prop, you can get it for as little as $250, or less.

The Yamaha branded versions use a press-in rubber hub. The Stiletto and Turbo branded versions use a square-bore style hub kit.


Important information on engine mounting from the same thread:

Your Yamaha 150 has four sets of mounting holes in the motors mounting bracket. In 1989, that motor would have properly been mounted using the second set of holes in the position we call "One Hole Up"

o <-- Bolts through this hole, motor mounted "All The Way Down"
o <-- Bolts through this hole, motor mounted "One Hole Up"
o <-- Bolts through this hole, motor mounted "Two Holes Up"
o <-- Bolts through this hole, motor mounted "Three Holes Up"


With a modern stainless steel propeller, the preferred position on the Outrage 18 is "Two Hole Up"


o
o
o <-- Bolts through this hole, motor mounted "Two Holes Up"
o

In general, the theory on motor mounting height is to have it set as high on the transom as possible without the propeller loosing grip and ventilating. But this varies from propeller model to propeller model, and to the type of boat and the purpose and speeds at which it used.

Boston Whalers are very middle of the road performance boats so we do not need to consider the needs of high performance, high speed applications where exotic propellers are used. And with your motor, there are only four choices anyway and we know the first one is too low.

With the motor mounted higher, there is less gearcase in the water and less drag. The difference between one set of holes and the next is 3/4" yet even that small a distance can have a profound effect on speed and handling.

Not only will less drag mean more speed, it will also mean better fuel economy as well as lighter steering effort.

The bow will rise less on acceleration because the lever arm of the motor is shortened.

The reduced draft also means a reduced chance of a propeller strike.


The entire thread can be reviewed for additional information: http://continuouswave.com/ubb/Forum4/HTML/007847.html
1992 Outrage 17
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jimh
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Re: Re-power OUTRAGE 18 on a Budget

Postby jimh » Thu Oct 25, 2018 9:04 pm

The propeller markings you describe as "M21" sound like a 21-pitch. That may be somewhat tall for the OUTRAGE 18. We need to know the engine gear ratio.

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Re: Re-power OUTRAGE 18 on a Budget

Postby dtmackey » Thu Oct 25, 2018 10:28 pm

The Yamaha carburetor 150, 175, 200 models are all the same 2.6-liter block, and they are one of the best running motors out there. I've owned two over the years, and Yamaha carbration is spot on. They idle smoother than any other carburetor motor out there, so you will not be disappointed.

Post-1993 is when they changed the shift shaft from steel to stainless and that was the only major concern I can think of. My first was a 1987, the second was a 1994 I believe.

D-

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Re: My newly acquired 1987 OUTRAGE 18 in Great Condition

Postby jimh » Sat Oct 27, 2018 5:59 pm

This article was in reply to a post that gave the engine gear ratio.

For a 150-HP engine with 1.85:1 gear ratio to turn a 21-pitch propeller to 5,500-RPM with about SLIP=5 would suggest 56-MPH boat speed

For a moderate V-hull boat with 150-HP to reach 56-MPH with a Boston Whaler Outrage hull with hull constant about 180 would require the weight to be only 1,550-lbs.

I am certain the OUTRAGE 18 is going to weigh much more than 1,500-lbs, and that means the engine will never turn a 21-pitch propeller to its rated maximum engine speed.

Again, my suggestion for an initial propeller to try is a three-blade Yamaha steel propeller with 17-pitch.

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Re: My newly acquired 1987 OUTRAGE 18 in Great Condition

Postby Jefecinco » Sun Oct 28, 2018 10:33 am

Jetfishing seems to be an eccentric type of person.
Butch

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Re: My newly acquired 1987 OUTRAGE 18 in Great Condition

Postby jimh » Sun Oct 28, 2018 10:55 am

Phil, dtmackey: thanks for trying to help this fellow. He seems to have gone away and deleted all his posts.

Butch: since starting this website in 1994 more than 40,000 people have participated. That is a large population, so the range of behaviors exhibited by those participants is similarly large.