Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

I am trying to find the proper gasket and ring parts for my powerhead. $500 seems a bit too much. So, looking for parts is a tall order to fill.
 
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wired247

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

Ive stuck motors using wisecos during the initial break in. Luckily no permanent damage but like faztbullet said until they go through a bunch of heat cycles they can be temperamental. Sub 7000 RPM motor go with cast pistons. Forged pistons in a 3 cyl are a waster of money.
 
ib18

ib18

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ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

Ok, I want to replace my mercury 90hp with Johnson 90 hp, do I need to drill new holes?

Both have power trim tilt
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

item 4 was a broken AGC fuse, so need to buy a 7.5 amps AGC fuse, for now, I just replaced with a 5 amps AGC fuse to prove it was the fuse - https://www.youtube.com/watch?v=pnUPvG0rkxo

It is a west marine aurora VHF marine radio - working, will have to test it on the water
 
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TD_Maker

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

ib18 said:
Ok, I want to replace my mercury 90hp with Johnson 90 hp, do I need to drill new holes?

Both have power trim tilt
Click to expand...

Are you not going further on the Merc. 90 rebuild? To answer your question, the holes drilled for the Mercury are the same as the Johnson 90. I also went from the Merc to a Johnson 90.
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

yes, i am waiting for the machine shop to fix it. Ralph said another 2-3 weeks and he wants me to send another $150. He already got my $30 deposit. I am thinking about taking it to another machine shop, because I don't like Ralph keep asking me money for the job.

This motor will cost me around $1G when i am done with it. So, looking for cheap alternative when I have to.
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

This is the Johnson 90hp V4 that I will pickup tomorrow. Do you know which year is this motor?

The 2 numbers I can see are J90NLCNB, J5686362

Johnson1.jpg
Johnson2.jpg
Johnson3.jpg
Johnson4.jpg
 
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TD_Maker

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

I am pretty sure the Johnson 90 is a 1982 model....at least according to the welsh plug numbers.

Just be forewarned. Changing from the Mercury to the Johnson is not just a simple "Bolt-it-Up type deal. You will need to change your controls and cables...along with the wiring harness of course. You will probably be able to use your Tach again...just change the pole settings. Steering cable should be the same....will have to change the steering arm however.
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

TD_Maker said:
I am pretty sure the Johnson 90 is a 1982 model....at least according to the welsh plug numbers.

Just be forewarned. Changing from the Mercury to the Johnson is not just a simple "Bolt-it-Up type deal. You will need to change your controls and cables...along with the wiring harness of course. You will probably be able to use your Tach again...just change the pole settings. Steering cable should be the same....will have to change the steering arm however.
Click to expand...

yes, got the control box and key. Forgot about the key, so went back to get it. We almost lost the motor, hoist and crab boat - engine hoist almost fell into the sea - YouTube
 
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ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

I will be changing the impeller this weekend, so do i need the lower unit seal kits?

Fix lBuy water impeller kit ($30) and lower unit seal kits ($44). - Do I really need the LU seal kit?

impeller kit - New Mercury Water Pump Impeller Kit for Outboards 47 43026T8 47 43026T6 18 3214 | eBay

Lower unit seal kit - Lower Unit Seal Kit Mercury Mariner Outboard 30 125 HP 18 2626 26 43035A4 | eBay - $43.99+FS
 
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ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

Bad news, Ralph told me my 3rd and bottom cylinder was so out of whack that he bored to the next 2 size over and now it needs a new sleeve or just a new block.

I will start looking for a new block or sleeve, but either way it will cost me more than $300 now.

Good thing, I picked up a 90hp Johnson outboard earlier for now so I can go out fishing sooner rather than waiting for this motor.
 
Faztbullet

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

Ralph told me my 3rd and bottom cylinder was so out of whack that he bored to the next 2 size over
Click to expand...

What did he bore it to???? The next size from .015 would be .020 next is .030 and last at .040.
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

good question, i will ask him again tomorrow. He did say he bored it twice over. it was 15 over when i bought it, so he bored it twice over. Not sure if it is .03 or .04. He just told me it was done. No piston can fit it anymore unless i can find a sleeve.
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

I also found this block on ebay for $149 free ship. 1989 merc 90hp needs to be bored too....scared.....

Mercury Outboard 70 80 90 HP 3 Cylinder Block 876 8947A24 Powerhead | eBay

So, $149 to get this block and Have Ralph bore this again for $149. So I get a good working powerhead with $300 back to my original cost - this should work for me.

What do you think?
 
Faztbullet

Faztbullet

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

After you get new/used block , take it to someone else other than ralph as only way that cylinder would have not cleaned up is if it had a deep groove in it.....
 
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oldman570

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

Faztbullet said:
After you get new/used block , take it to someone else other than ralph as only way that cylinder would have not cleaned up is if it had a deep groove in it.....
Click to expand...

^1 as to finding another machine shop.
I believe the blocks of the 70,80 &90 from 1987 to1990 ,or shortly after, are the same, The one on Ebay should work as long as it is of that vintage. Do a SR# search of the year before buying, or ask the seller what year the block is from. JMO
Oldman570
 
ib18

ib18

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Re: Rebuilding Mercury 90 hp 2 cycles 3 cyclinders (1987) - 100, 100, 75 psi

problem with ebay motor is a freshwater instead of saltwater, does it matter?

I can get the powerhead $149 plus 2 standard bore pistons for $60 ebay, the third new piston will be $100

$300 plus $160 - so almost $500 for the block/pistons alone. still need to put it together. ai ya ya
 
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