getting more speed out of 90 hp johnson

Joined
May 15, 2010
Messages
52
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
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
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.
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: getting more speed out of 90 hp johnson

My 90 does 40, that's pretty good for a 90
 

watergecko

Petty Officer 2nd Class
Joined
Dec 1, 2010
Messages
111
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.
 

Sixmark

Master Chief Petty Officer
Joined
Jul 11, 2010
Messages
890
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.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
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 :D
 
Joined
May 15, 2010
Messages
52
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.

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
 

V153

Lieutenant Commander
Joined
Apr 16, 2011
Messages
1,764
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!
 

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kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
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.
 
Joined
May 15, 2010
Messages
52
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.

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?
 
Joined
May 15, 2010
Messages
52
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
 

Joshua Nichols

Lieutenant
Joined
Jun 29, 2009
Messages
1,431
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
 

hidef

Lieutenant
Joined
Aug 22, 2009
Messages
1,465
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.
 

PWH1

Petty Officer 3rd Class
Joined
Jan 11, 2010
Messages
78
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
 

Sixmark

Master Chief Petty Officer
Joined
Jul 11, 2010
Messages
890
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!


OK all of us could gain extra performance by doing mods to our motors, let's keep things in perspective.
 

archcycle

Chief Petty Officer
Joined
Sep 21, 2009
Messages
647
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 :rolleyes:

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.
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: getting more speed out of 90 hp johnson

gotta be newer than 83, 83 didn't have vro.
 

sw33ttooth

Chief Petty Officer
Joined
Apr 24, 2011
Messages
498
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.
 
Joined
May 15, 2010
Messages
52
Re: getting more speed out of 90 hp johnson

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
 

AEROCOOK

Master Chief Petty Officer
Joined
Jul 28, 2004
Messages
872
Re: getting more speed out of 90 hp johnson

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.
 
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