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Old 07-04-2015, 17:07   #16
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Re: Yamaha 9.9 chruising rpm

I once pushed my 40 foot commercial longliner about 10 miles against the tide with my 12ft inflatable with a 15 hp Johnson, after getting a wad of longline gear wrapped around the shaft (which broke the shaft coupling).

Once I got it moving, it only needed 1/2 throttle to move it as fast as it would go. More power had no effect on the 30,000 lb boat. I was amazed at how little gas it took at half power with that load.

Love those 2 strokes!
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Old 07-04-2015, 19:35   #17
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Re: Yamaha 9.9 chruising rpm

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Originally Posted by Hyrdflyr View Post
I once pushed my 40 foot commercial longliner about 10 miles against the tide with my 12ft inflatable with a 15 hp Johnson, after getting a wad of longline gear wrapped around the shaft (which broke the shaft coupling).

Once I got it moving, it only needed 1/2 throttle to move it as fast as it would go. More power had no effect on the 30,000 lb boat. I was amazed at how little gas it took at half power with that load.

Love those 2 strokes!


That's awesome this gives me hope my 9.9 high thrust will push 6,500 lb well.
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Old 08-04-2015, 06:53   #18
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Re: Yamaha 9.9 chruising rpm

My 9.9 HT Yamaha from 1997 pushes my 11,000 lb 26-foot power boat effectively at 1/2 or 3/4 throttle, even in a good breeze. Only about 4.5 knots max though. Great for get home, or salmon trolling (at less than 1/2 throttle). Provides some battery charging too. Thrust improved a bit when I added a ring-shaped prop saver (somewhat of a Kort nozzle effect).

I don't bother running at WOT because it won't go significantly faster anyway, and the kicker doesn't sound very happy.
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Old 08-04-2015, 07:49   #19
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Re: Yamaha 9.9 chruising rpm

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Originally Posted by valhalla360 View Post
It's not recommended to run at WOT all the time. Doing it occasionally isn't a big issue but long term, it puts wear a lot of wear on the engine.


It's not a situation where the engine will explode after 30min at WOT but you will be shortening the life of the engine.
I bring mine to wide open, then throttle back just a crack.

The thing with outboards is they are not built like regular inboards, car engines, air plane engines or anything else. They run on needle bearings and not friction bearings. They are designed to be able to be run hard. Essentially they are high performance and strong engines especially if you look at how many hp they squeeze out such a small amount of CC's.

Running outboards hard is perfectly ok. Running regular inboard gas motors that hard causes issues. Don't forget inboard engines are built more for torque (lower rpm) where outboards dont have nearly the torque but are meant to be more for speed (high rpms)

The only caveat to all of this is when pushing a displacement hull maxing out the rpms usually doesnt gain you a ton of speed and at that point really is just wasting gas. Match how you run the outboard on your sail boat to how much gain you actually get in speed.

i.e. if at 3/4 throttle you get 5 knots and max throttle you get 5.5kts then stick with 3/4 the extra rpm is just burning gas and not really moving you that much faster.
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Old 08-04-2015, 08:08   #20
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Re: Yamaha 9.9 chruising rpm

Every outboard belonging to a sailor that I've ever heard of died of corrosion (electrical or on the cooling side) rather than use. Some seized after running out of oil... that drained out of a corrosion hole.

I doubt it really matters unless this is very frequent use. I've certainly run 9.9s for days in a row WOT.
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