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  1. #1
    Seaman
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    Default getting more speed out of 90 hp johnson

    i just got the deal of a lifetime yesterday. i bought a 1990 16 ft. sunbird fish/ski with a 90 hp johnson outboard. it just had the carbs redone and a frsh tune up. it had sat for over a year and a half so i had to drain all of the gas out of it and put a new battery in it. after that was done it fired right up. i took it down to the waterway and had a blaste on it. it ran a solid 40-45mph and gets out the hole pretty quick..what i would like to know is if a jack plate is going to give more speed and a quicker hole shot. it has a stainless prop on it and dont know the pitch. could someone tell me how to find that out.
    also it is not spitting the water out of the motor like i thought it is supposed to. does this particular engine do that. it is a 2 stroke and has 2 separate tanks for the oil and gas and mixes automatically..any suggestions to make this thing run top notch please let me know.
    i wasnt even going to buy another boat this year but this was too good of a deal to pass up..thanks

  2. #2
    Fleet Admiral HighTrim's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    What year/model 90hp?

    If it is new to you, and has been sitting, replace the impeller.

    Look on the inner lip of the prop hub for a stamped number. What was you WOT RPMS? Post the pitch when you find it.

  3. #3
    Vice Admiral bktheking's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    My 90 does 40, that's pretty good for a 90
    Signature- If you have fuel and spark- Have you checked compression?

  4. #4
    Petty Officer 2nd Class watergecko's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    Just find some down hill water and youll b fine. Seriously tho, make sure you have a good tell tale before beating on that motor. If you have the vro, you should have a tell tale.

  5. #5
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    Default Re: getting more speed out of 90 hp johnson

    Just how much more speed are you expecting? 40-45mph out of that 90 is pretty good if you want much beyond that then you might be looking at breaking out the wallet and your deal of a lifetime would become the deal that was.
    1985 Baretta Vanguard 16ft & 1984 Evinrude 75hp O/B

    ****Running your motor without water is like peeing into the wind, it's a stupid impulse that is going to be a mess later****

  6. #6
    Supreme Mariner kenmyfam's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    What they all said !!!!
    The best way to get more out of your 90HP is to make sure you are set up correctly (motor height, WOT RPM, loading of the people and gear on board and making sure it is tuned up properly)
    Beyond that the best way to get more from your 90 HP is to trade it in for a 115 HP or above
    Marada 2100 Executive Series, 5 Litre V8 with Mercruiser Alpha 1 outdrive. 2007 K-Z Spree 260 RBH, all = a whole lot of family fun !!!!

  7. #7
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    Default Re: getting more speed out of 90 hp johnson

    Quote Originally Posted by watergecko View Post
    Just find some down hill water and youll b fine. Seriously tho, make sure you have a good tell tale before beating on that motor. If you have the vro, you should have a tell tale.
    it is the VRO V4 engine..as far as how many people and equipment on board, it was just me and my lady and a cooler. as far as the rpms, the tach isnt working. i have to look and see if i can get that going. i have only taken it out the one time because i just got the boat monday.
    one thing i am also very concerned about is if there should be water streaming out of the engine while it is running. i always thought engines the mix the oil and gas should have that. this is the first time i have ever owned a outboard but not my first boat.
    also should this boat burn alot of gas? i will check the pitch on the prop and post it later..thank you for everyones replies..i love this site
    oh yeah and it is a 1990 johnson vro v4

  8. #8
    Lieutenant V153's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    First fix the tachometer.

    Yes there should be water coming from the pee hole. And yes the V4s can burn an obscene amount of fuel 'specially when yer gettin on em.

    I too would recommend starting with a fresh impeller, but then again if you're not getting high temp alarms, providing your alarm(s) work. It's entirely possible there's an obstruction in the tattle-tail hose or fitting. Might could be a worm or a bug holed up in there. It happens.

    Ya y'oughta be able to find a # stamped/etched into the prop somewhere. Can you post pics?

    Might surprise some as to just how much performance you can get outa a 90 when it's rebuilt, balanced, and/or dialed in right. This slightly modded '86 has pushed my boat to just under 55mph @ about 6200rpm.

    Just 'member to use good oil & gas. I run Sunoco premium & Quicksilver synthetic in mine.

    Good luck on your quest!
    Attached Images Attached Images
    1981 Baja 15SS_1983 Johnson 140_62.9 mph
    1981 Glastron/Carlson C500 metric series_Modified 1978 Evinrude 140_Project
    1971 Glastron V153_1986 Evinrude 90_54.8 mph_Rebuilt then unceremoniously wrecked
    Walk Tall And Carry A Big Bilge Pump

  9. #9
    Supreme Mariner kenmyfam's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    If you don't "know" the motor then give it a basic health check, change the impeller and the lower unit oil.

    Oh and I would suggest getting an OEM manual.
    Marada 2100 Executive Series, 5 Litre V8 with Mercruiser Alpha 1 outdrive. 2007 K-Z Spree 260 RBH, all = a whole lot of family fun !!!!

  10. #10
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    Default Re: getting more speed out of 90 hp johnson

    Quote Originally Posted by kenmyfam View Post
    If you don't "know" the motor then give it a basic health check, change the impeller and the lower unit oil.

    Oh and I would suggest getting an OEM manual.
    checked with the machanic and the lower unit oil and impeller have both been changed. it was used once since all of that was done. i personally know the last owner and know its history. the mechanic is certified and works at a reputable shop. my concern is the water peeing out of the engine. what should i check. i am a tattoo artist and work crazy hours because it is coming into the busy season so i dont have the time i would like to have to mess with this thing. i have been cleaning and getting everything tightened every night for the time i have left in a day..
    where will i get this manual from?

  11. #11
    Seaman
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    Default Re: getting more speed out of 90 hp johnson

    will it hurt the engine to change from the reg 2 cycle oil to 2 cycle synthetic. i always heard that in a car u should use it from the first oil change but dont switch to it. will the premium gas make the engine run better? also the tach isnt working where does that hook to on the engine? i need to get that working. it worked when i first took it out..any suggestions will help and thanks for all of ur responses

  12. #12
    Lieutenant Joshua Nichols's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    Is this GPS speed or wishometer speed??? Cause I can't think of much more you could want out of it.. Thats moving right along...
    I guess you could alway hang more engine off the back..

    ALL 2 stroke outboards drink the fuel.. They like it.. ALOT


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    only thing GM I own.. Of course it's the only one that gives trouble..
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    Hope all you want.. It won't get it fixed..

  13. #13
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    Default Re: getting more speed out of 90 hp johnson

    As long as the two cycle oil has TC-W3 printed somewhere on the bottle you will be okay. Your outboard has a tell tale on the right side of it that should be squirting water that indicates the water pump is working. When running at full throttle there will also be some water coming out of the exhaust reliefs in the leg but most of the water comes out through the prop. 45 MPH is respectable for a 90 if you want to go faster you need to go to a larger outboard. You should find out why the tach isn't working it could be the tach itself or it could be the voltage regulator.
    I love the smell of a two stroke early in the morning

    Currently running a 1971 Starcraft JetStar powered by an E35QLEDC with the OMS removed and a 4436R

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  14. #14
    Seaman PWH1's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    I as well have a 16' boat with a 90 Johnson SPL. My motor is well tuned and I believe I am getting the best it has to offer. Below are results based on a prop change I made last year. The prop change really brought the motor to life as well as has it running at optimum RPM range. Since out applications are pretty much the same, this should give you a good measure once you find out what your existing prop is.

    Old prop 14X17 Michigan Wheel:

    Top speed = 34 mph (GPS)
    RPM = 4600

    New prop 13 1/4 x 17 Solas:

    Top speed = 42 mph (GPS)
    RPM = 5300/5400


    1997 Glastron GS-160
    Johnson 90 SPL

  15. #15
    Master Chief Petty Officer
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    Default Re: getting more speed out of 90 hp johnson

    Quote Originally Posted by V153 View Post
    First fix the tachometer.

    Yes there should be water coming from the pee hole. And yes the V4s can burn an obscene amount of fuel 'specially when yer gettin on em.

    I too would recommend starting with a fresh impeller, but then again if you're not getting high temp alarms, providing your alarm(s) work. It's entirely possible there's an obstruction in the tattle-tail hose or fitting. Might could be a worm or a bug holed up in there. It happens.

    Ya y'oughta be able to find a # stamped/etched into the prop somewhere. Can you post pics?

    Might surprise some as to just how much performance you can get outa a 90 when it's rebuilt, balanced, and/or dialed in right. This slightly modded '86 has pushed my boat to just under 55mph @ about 6200rpm.

    Just 'member to use good oil & gas. I run Sunoco premium & Quicksilver synthetic in mine.

    Good luck on your quest!

    OK all of us could gain extra performance by doing mods to our motors, let's keep things in perspective.
    1985 Baretta Vanguard 16ft & 1984 Evinrude 75hp O/B

    ****Running your motor without water is like peeing into the wind, it's a stupid impulse that is going to be a mess later****

  16. #16
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    Default Re: getting more speed out of 90 hp johnson

    I have a deep V hulled 16'. The first motor on it was a 90hp. When pushing it past 40mph in choppy waters I could never help but think about how well thought out that 90hp max USCG plaque was

    Larger motor now, and I still think the plaque was right! Any faster and it might take off if you hit the wrong wake or wave! That would be bad. You don't want that.

  17. #17
    Vice Admiral bktheking's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    gotta be newer than 83, 83 didn't have vro.
    Signature- If you have fuel and spark- Have you checked compression?

  18. #18
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    Default Re: getting more speed out of 90 hp johnson

    i had an 82 v4 that used 6 gallons in 1 and half hours a bit of a speed freak get the tach fixd so your sure your rpm's are in good range or you'll blow the motor.
    repair shops are for the rich and lazy, want something done right? do it yourself.
    with knowledge grants perfection

  19. #19
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    Default Re: getting more speed out of 90 hp johnson

    Quote Originally Posted by bktheking View Post
    gotta be newer than 83, 83 didn't have vro.
    the motor is a 1990 not a 1983. thanks everyone for all of your responses. will a aftermarket car tach work for this boat or do i need something that is marine. is there a way to tell if the pee hole is clogged. i guess i will have to take the cover off and follow the hose. it did have the water coming out of the exhaust above the water. it just isnt coming out of the pee hole.
    thanks for the info on the drinking gas. this boat has a fresh tune up and i thought something else was wrong. i was running it real hard too

  20. #20
    Senior Chief Petty Officer AEROCOOK's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    Quote Originally Posted by boatingtattman View Post
    the motor is a 1990 not a 1983. thanks everyone for all of your responses. will a aftermarket car tach work for this boat or do i need something that is marine. is there a way to tell if the pee hole is clogged. i guess i will have to take the cover off and follow the hose. it did have the water coming out of the exhaust above the water. it just isnt coming out of the pee hole.
    thanks for the info on the drinking gas. this boat has a fresh tune up and i thought something else was wrong. i was running it real hard too
    Has to be a boat tach. Try finding an OMC one since it will plug right in. Before you waste money on the tach you should test your rectifier because it may be why your tach isnt working. Like Kenmyfam said, get a factory manual, it will tell you how to test the rectifier. As for the tell tale, poke a wire up into it to see if it's plugged, mine was plugged with mud from some insect.

  21. #21
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    Default Re: getting more speed out of 90 hp johnson

    Old thread but heres my 90 story. 1981 Checkmate Enticer. Crank rated 90 HP . In a way I am the original owner. I went down with my dad to pick it up at the dealer in 1981 and Ive done all the maintenance and most of the driving since it was new. Last year I gutted it and replaced the interior.

    We ran that boat forever with the 19 pitch OMC stainless prop as the primary prop. On the lie-o-meter it showed 53 at 5800 back in the day. It still shows that since it was restored ( and speedo changed ) but the GPS ( 3 different ) is saying 49 mph with that prop. We skied with it for years, pulled tubes and had 4-5 people in the boat doing it. Recently I put a set of 140 Johnson heads on it and a 17 pitch 4 blade Solas stainless prop. It pulls like a tractor and tops at 46 mph on the GPS . With the 19 pitch it should be even faster and I'll try it out saturday. I'm not saying all 90's should run like this. I'm sure most don't but I have great compression on all the cylinders and heres the most important part . In 1981 Johnson just figured they'd put 1 5/16" carbs on everything. Later they started really cutting back on venturi sizes which helps out on lower end but doesnt do much or the top end. Ive seen late 115's ( same as the early 140 ) that had 1 3/16" carbs and late 90's with 1 inch carbs. Find yourself some 1 5/16 carbs and jet them per 1981 standards. A set of 78-82 140 heads and it'll really wake up. JOHNSON FLOAT LEVEL IS VERY IMPORTANT. Do it right.

  22. #22
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    Default Re: getting more speed out of 90 hp johnson

    What is it with the 140 head? Is it a bolt on? Makes it more compression?
    Just like to know since i own a 90hp 1991.

  23. #23
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    Default Re: getting more speed out of 90 hp johnson

    The 140 heads bolt on and add more compression. 5 psi more per hole or so. Good for a few miles and hour ,better idle and a snappier throttle.

  24. #24
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    Default Re: getting more speed out of 90 hp johnson

    Wow, that is great to know.
    I am not so familiar with outboards, more with crossbikes
    But just to be sure, you are talking about a 1981 motor, i am having a 1991. I reckon i have the smaller carbs aswell. Have to check that.
    I wld do it just to get a better low end and better idle. Also can you tell me what prop it was? Brand diameter? Thx Wired.

  25. #25
    Chief Petty Officer toddschubert's Avatar
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    Default Re: getting more speed out of 90 hp johnson

    Quote Originally Posted by Fisherman1010 View Post
    Wow, that is great to know.
    I am not so familiar with outboards, more with crossbikes
    But just to be sure, you are talking about a 1981 motor, i am having a 1991. I reckon i have the smaller carbs aswell. Have to check that.
    I wld do it just to get a better low end and better idle. Also can you tell me what prop it was? Brand diameter? Thx Wired.
    You are hijacking thread. Start a new one
    It's a possibility!
    Love my '93 88spl Johnson and '93 Larson bow rider

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