getting more speed out of 90 hp johnson

wired247

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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.
 
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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.
 

wired247

Lieutenant Commander
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Messages
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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.
 
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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.
 

toddschubert

Chief Petty Officer
Joined
Sep 3, 2011
Messages
504
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.
You are hijacking thread. Start a new one
 

toddschubert

Chief Petty Officer
Joined
Sep 3, 2011
Messages
504
Re: getting more speed out of 90 hp johnson

Youve got to get that water flow issue solved before moving on. A water pump impeller can go bad just sitting. Use a small piece of wire while running on muffs to stick in pee.hole
 
Joined
Jun 10, 2011
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Re: getting more speed out of 90 hp johnson

Toddy, Is not the thread about getting more speed out of a 90hp :confused:
 
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