Slow 9.9 Mercury

Quallsj

Cadet
Joined
Apr 18, 2021
Messages
9
That certainly isn't the optimum position, but it's not what's causing your slow speed. You're not running a little slow, you're running a lot slow.

OTOH, the difference between an 8 and 9 pitch probably won't triple your speed either.

Buy what the prop selector tells you, or look at a Michigan catalog and see what their recommendation is based on boat size. You need a new prop anyway. Then, verify that both cylinders are running.
Thank you. I just now saw this. I appreciate the info.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,930
A neon one will not change colors and will flash at weaker voltages. Just cause it flashed does not mean it has the correct voltage to produce a arc bridge under compression.
 

WesNewell

Chief Petty Officer
Joined
Jan 3, 2018
Messages
497
Hi. I have a 2005 Mercury 9.9 that seems to run great EXCEPT the boat is extremely slow relative to what that motor should do. It's running maybe five or six mph loaded. I noticed the anti-ventilation plate is 1 3/16" below the bottom of the boat. Could that alone cause such a drastic drop in speed? Thanks!
No.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Noticed the anti-ventilation plate is 1 3/16" below the bottom of the boat. Could that alone cause such a drastic drop in speed? Thanks!

That setting it's relative, You will see a drastic speed drop and a back water splash if the water flow at speed bangs against the upper middle leg area...

03.JPG

Ideal is for water flow to pass right under the mall upper plate or above the AV plate which it's a matter of personal preference. Right now with such low displacement speed won't know at which lower leg is the hardened flat water flow is passing by, must check that visually when combo finally runs on plane at speed. You're losing too much precious boating fun time figuring it out way too long...

Happy Boating
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
The position of the motor in the above photo is without a doubt the worst installation I have ever seen. That motor needs to be raised up at least a foot.
Really, with due respect you definitely don't know what you're talking about by simply watching a pic, why would you need to raise the motor for, where do you think that with such setting is the water flow passing by ? give your best wild guess, this is where geographical location and boating area comes into play and it's of extreme importance if wanting to take the best of that combo which have managed doing so...

Happy Boating
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
I'm open going for a further tech discussion endorsing such motor height installation and the prupose of it with proven tech facts if wanting to go that route, if not will leave it there....

Happy Boating
 

JimS123

Fleet Admiral
Joined
Jul 27, 2007
Messages
8,235
I'm open going for a further tech discussion endorsing such motor height installation and the prupose of it with proven tech facts if wanting to go that route, if not will leave it there....

Happy Boating
This topic has been discussed to death already. Proper setup has been pointed out with facts many times.

These forums are intended to help people. It just worries me that some novice will look at a motor setup and take it for gospel.

We'll just have to agree to disagree.

Finally, as I have said many times, it really doesn't matter whether a person is right or wrong, or if their setup is optimum or a disaster, the only thing that matters is whether you are satisfied with what you have.
 

WesNewell

Chief Petty Officer
Joined
Jan 3, 2018
Messages
497
The density of water is ~784 times more dense than air. Therefore any excess of the lower unit below the waterline produces a lot of drag. It also introduces the increased hazard of the lower unit hitting something below the water surface damaging the lower unit or causing major injury or death to boaters at high speeds. I implore everyone to not listen to the BS put out by Sea Rider.
 

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Sea Rider

Supreme Mariner
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Sep 20, 2008
Messages
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As you have posted your personal appreciations with respect of my posts I'll ask : If you guys run large HP, short gap plates, bolt on motors with electric trim, boating with heavy boats heavy loaded while being driven with a wheel and remote box installation what the you know what are you doing in the portable, tall plate's gap, manual trim and steering motors powering light to medium light boats such as Sibs, Ribs, Flat boats, Boston Whaler section ?

Hey WN, as you have warned and implored the I'boats boating community not to listed to my BS posts, don't expect a kind answer from me in retribution. Let me tell you that you're no reference to listen to either, you have your own repetitive BS posting which will be useless listing and posting...

Tohatsu-Merc 9.9.JPG
Only a complete moron will dare make an idiotic comparison between a large HP motor and a portable one, check the gap difference between both, there's nothing in common between both except a prop. That tells how much you know about portable motor behaviour in water with whom you've never worked before. With my disrespect, better concentrate on what you think you know and bug-off from my posts.

How does a geographical location and boating area accounts for top water performance whether the water flow at speed passes under the upper plate or over the AV plate. For the ones that doesn't know me, I'm located in Peru and as you probably know if have studied geography at school the Humbold Current runs north along more than 2.5 kilometers of coast. When off coast boating in flat calm no wind water cond the motor won't care at which lower leg is the water flow passing by at speed.

Moderate Chop.JPG

In moderate to heavy chop windy water conditions is where the severe prop aeration starts and you would't want your motor running with the AV plate set that low due to : will take very long to reach your final destination while not being able to increase the speed and probably screwing your motor revving as high as much as 7 K rpm constantly for long time periods.

Heavy Chop.JPG

On such windy choppy water conditions running the motor's upper plate to skim the water flow right under it will totally cancel the prop aeration, the prop will achieve its best thrust and if running a maximized prop the better.

Keep in mind that light boats as described running tall gap plates motors will have a jumpy ride under such water condition and excessive prop aeration issues. Would you say this is another BS of mine ?

Bottom line, let new boaters requesting best motor/transom match experience by themselves both mentioned plate's parameters according to their own geographical location and their boating area such as : a river, lagoon, lake open sea whichever they will be boating at and whichever plate setting suits them best....

Happy Boating
 

JimS123

Fleet Admiral
Joined
Jul 27, 2007
Messages
8,235
Your "gap plate" comparison is flawed data. My collection of 69 outboards covers the range of 0.75 to 150 horsepower, over a chronology of 100 years, and with few exceptions (where there was no gap......LOL) the gap plate is the same. Your middle aged Merc photo is either an anomaly or the pic was photoshopped for some obscure purpose (or Merc screwed the pooch in that time frame).

Other than being in Saltwater, your choppy conditions looks like my normal Sunday afternoon. Granted, we try to boat during weekdays when the wind and traffic is much lighter, and thus we optimize our rigs for those usual conditions, but if it gets squirrely we simply adjust our speed accordingly and all is good.

The more I think about it, maybe rubber boats act differently. I realize they are cheap, but a real boat can be had for the same price if you buy a well maintained used one.

Some of us died in the wool boatmen with big boats and motors that we spend tens of thousands of dollars on strive to optimize under all conditions. OTOH, a working stiff that only has 1 day a week to go fishing with his family in a 14' tinny doesn't really need an induction tach to improve his speed by 1 mph or his fuel economy by 0.1 mpg. Life is too short to worry about it.

"TOES IN THE WATER,
ARSE IN THE SAND,
NOT A WORRY IN THE WORLD,
COLD BEER IN MY HAND...
(Life is good)"
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,930
Arggggh!!! Here it is again....
Facts to ponder....
A) the higher the motor the more efficient it is. This is due to less drag in water
B) less prop blades in water(a prop is most efficient with 1 to 1-1/2 blades submerged).
C) rounded part of lower unit housing actually provides stern lift
D) all the above can lead to a pitch and RPM increase which = more MPH
E) This will apply to 75% of ALL boats made less dingys and ducks

Here is the Corp's work boat that I tinkered with last week..60 knots top speed.
 

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JimS123

Fleet Admiral
Joined
Jul 27, 2007
Messages
8,235
Love this video..a perfect example of High HP and engine height and prop surfacing...just 12-13% slip at WOT. Will this work fro a 9.9...not quite but 1ich below bottom is a god all around set up.The deeper the motor the more drag and less speed/RPM.
Fastbass Marine TV - Sportsmaster Lower Testing #3 - YouTube
This one good too..
Bob's Machine - Running shallow with Action series Jack Plate & Nose cone! - YouTube
12% is basically a new factory setup. That's what I had at the start. With a little optimizing I got it down to 8%.
 
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