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Johnson 90 to 140 conversion.

TheNerd said:
Pretty interesthing trying to squeeze the ponies out of those motors, but wouldnt it be easier to pick up a 150 or 200 merc. Could sell what you got and pick up a motor ready to go, just bolt on. An old guy once told me if I wanted something faster, sell what I had and buy something faster, trying to make something faster will cost more in the end. He was right. I have learned the hard way a few times. Just my 2 cents.
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It will cost me less than $1000 to build a 140 including the cost of the core 140 and spare lower unit plus I get to keep the 90 that came off the line with the boat Ive been dragging around for 31 years . That 140 engine will be as fresh as the day it rolled out of the factory. It will go as fast as I want it to go and will probably last until I give it to my kids in 20 years. I'm a mechanical engineer with a machinist background. Ive built hundreds of engines, transmissions and differentials and Ive designed and built industrial machinery and production processes ethat makes all of those look like tinker toys. 2 cycle Johnsons arent the most difficult thing in the world to make work well. I just want to go 60 MPH. Its not that big of a goal.
 
TheNerd said:
Pretty interesthing trying to squeeze the ponies out of those motors, but wouldnt it be easier to pick up a 150 or 200 merc. Could sell what you got and pick up a motor ready to go, just bolt on. An old guy once told me if I wanted something faster, sell what I had and buy something faster, trying to make something faster will cost more in the end. He was right. I have learned the hard way a few times. Just my 2 cents.
Click to expand...


I just spent the better part of the day tooling around with that fresh built 140 spec motor . I have to say that I am glad I dont expend any energy listening to old guys who don't have the slightest clue about what they are talking about. This thing is a kick in the ass! It sounds like a chainsaw on steroids when it gets opened up. I spent 4-5 hours just taking it easy but I did open it up a bit towards the end. With the 17 pitch pop I was hitting 52 mph at 6200 which is a full 1100 RPM over what it would do with the stock 90 . It could have gone for more but I didnt open it up all the way. Ive got a 21 pitch 4 blade on order that should push me over 60 with no set back or jackplate which is where I want to be. I dont run on smooth lakes. I run on the Columbia river and 4-5 foot swells come out of nowhere. I'll probably even drop my motor further down to keep it in the water when the rough stuff comes up.
 
Wired could you squeeze 50 more ponies out of my 2001 250 HP Evinrude? Make the 250 a 300 or better?
 
cmpulse170 said:
Wired could you squeeze 50 more ponies out of my 2001 250 HP Evinrude? Make the 250 a 300 or better?
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No, but I can turn a 140 into a 140. Tell you what take 7 sizes of your main jets. You'll have more power for a little while :).
 
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Great thread!

I have a 1994 "88 Special" on my little boat (same as the 90), and I was wondering if I can do something similar but less intrusive to gain some HP. I really don't want to do port work or anything.

What could I gain by just doing heads and carbs?

Thanks.

HD
 
hotdaddy27 said:
Great thread!

I have a 1994 "88 Special" on my little boat (same as the 90), and I was wondering if I can do something similar but less intrusive to gain some HP. I really don't want to do port work or anything.

What could I gain by just doing heads and carbs?

Thanks.

HD
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Youd gain quite a bit. put in intake stuffers, 1 5/16" carbs , 140 heads and some Carson reeds and that baby will perk right up. Youd gain even more with a 115 block . Yes, I have a good 115 block for sale :)
 
wired said:
Youd gain quite a bit. put in intake stuffers, 1 5/16" carbs , 140 heads and some Carson reeds and that baby will perk right up. Youd gain even more with a 115 block . Yes, I have a good 115 block for sale :)
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LOL.

I don't want to take too much apart until winter, but the heads and stuffers??, would be an easy start.

What are heads running these days?

HD
 
hotdaddy27 said:
Just checked Ebay...$100-$150. Sound about right?

are the 115/140 heads the same?

HD
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Nope. 140 heads are their own animal. Earlier the better. 78-79 are the best and 80-84 are second best but still good. Good for a couple MPH anyway.

Heres some '84s

http://www.ebay.com/itm/johnson-140..._Accessories_Gear&hash=item1c26afab41&vxp=mtr

heres a new starboard 140 head. Good deal for a new head actually.

http://www.ebay.com/itm/OMC-JOHNSON...tEquipment_Accessories_SM&hash=item3cc5fe29e1

And a used Port side

http://www.ebay.com/itm/1983-JOHNSO..._Accessories_Gear&hash=item5ae59636e7&vxp=mtr
 
10 or 15 HP for $100. I'll take that!

How is yours running. I will let you know if I make the move on the heads.

HD
 
hotdaddy27 said:
10 or 15 HP for $100. I'll take that!

How is yours running. I will let you know if I make the move on the heads.

HD
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Mine ran great but I sold the 90 powerhead and the 140 complete motor the other day. 150 Merc sitting on the back now.
 
I would have to say, doing all this work to a 90 may give it some performance gain, but to get a significant gain you really need to put the bigger ports in, as well, to correctly install the exhaust you need to machine the back of the block. Bigger carbs and higher flowing exhaust will be choked in the middle by small ports.

If you need any of the parts you have mentioned let me know I have all of them
 
Bill Gohr said:
I would have to say, doing all this work to a 90 may give it some performance gain, but to get a significant gain you really need to put the bigger ports in, as well, to correctly install the exhaust you need to machine the back of the block. Bigger carbs and higher flowing exhaust will be choked in the middle by small ports.

If you need any of the parts you have mentioned let me know I have all of them
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Those are the stock sized carbs for an '81 Johnson 90. The same holds true with the stuffers. They came in 90's in 1981. The higher compression definitely helps as well. With a stock 1981 90 HP Johnson and a bolt on set of 140 heads I was going 54 MPH GPS and getting very good mileage and better out of the hole by far than the 140.
 
Bill Gohr said:
I would have to say, doing all this work to a 90 may give it some performance gain, but to get a significant gain you really need to put the bigger ports in, as well, to correctly install the exhaust you need to machine the back of the block. Bigger carbs and higher flowing exhaust will be choked in the middle by small ports.

If you need any of the parts you have mentioned let me know I have all of them
Click to expand...

Bill,

I will probably be getting ahold of you at some point soon.

Would you mind sending me a PM with your phone number?

Thanks for the offer!

HD
 
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