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

[ib18]

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

It is leaking down when I bought the motor, so the previous owner used wood blocks to be sandwiched between the adapter plate and the trim bar to keep the motor up when he was on the road. I guess I will have to do the same.

 

[ib18]

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

Bump 1 on TD_Maker remarks. If the till/trim is working fine, do not mess with the unit. You might open up a can of worms that eats money quickly. The one cylinder dose have some buildup on the wall and can be cleaned up and honed if the ware is within limits. As others have stated, now is the time to do the job correctly and repair/replace everything that looks bad or you think needs attention. It will only save hard earned money in the long run. I never put my dirty shorts back on after taking a shower. JMO
Oldman570

thanks, yes, will take it to a machine shop to hone, bore etc. the cylinders and do it right so the motor can last another 10 years at least.

 

[ib18]

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

i got 2 problems this week, any suggestions?
1. GUNK does not seem to be able to remove the black carbon deposit on the 3 pistons after soaking them for an hour? should I soak them longer? or just go to walmart get a bucket of Superclean de-greaser? I will post the video later.
2. Do I need to totally disassemble the piston from connecting rod and disassemble them from the crankshaft before I can take it to the machine shop to bore, hone the cylinders?

 

[racerone]

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

Some shops insist on measuring the bores first.--Then they want the new O/S pistons before doing the boring.----They certainly do not need your old parts.

 

[ib18]

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

make sense to get new bigger over-sized pistons after boring the cylinders. Ah, all for nothing, good thing I just started, time to call the shop and bring the powerhead in for truth.

 

[ib18]

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

https://www.youtube.com/watch?v=0x4gAQUH4uw - cannot loosen the 3/8" bolts on the crankshaft and piston connecting rods,
need to get better tool for those 6 bolts so i can remove the 3 connecting rods/pistons.

Soaking the pistons to GUNK de-greaser, but not much success, so probably needs to soak them longer (24 hours?). Well, I don't think the top 2 cylinders need to be bored. so hopefully no over-size pistons needed for the top 2. just the bottom piston. So, will take apart the bottom 2 bolts for the bottom (#3) piston to remove the bottom (#3) connecting rod/piston.

 

[TD_Maker]

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

I am enjoying your videos. I admire how you just jumped in and started wrenching on this major rebuild. Keep plugging away.

 

[ib18]

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

Voila, progress. I was able to loosen the six 3/8 piston/rod screws. So, I have the 3 pistons separate from the crankshaft, called a machine shop. The owner wants me to bring in the cylinder block, so he can take a look and bore the 3 cylinders. I asked him how much. He said $150 for honing the first cylinder. $50 for each add'l. Parts are additional. Does that sound about right to you? I will have to do all the cleaning rods, pistons, assembling. He does no assembly work. otherwise, $800 for reassemble, cleaning, honing the powerhead everything. So, I will bring it to the shop if it is reasonable.

Do people reuse the bearing, needle pins?


https://www.youtube.com/watch?v=zPmD5Ei392I

 

[justchecking]

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

Ow! That sounds to high. In my area (Dayton, Ohio) I paid $80 TOTAL for one cylinder bored and three honed.

 

[ib18]

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

Wow only $80 in Ohio. I will (1) check out shipping charge to Ohio or FL (there seems to be a lot of them in FL) (2) call more shops in MD/DC/VA around me.

 

[Faztbullet]

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

Boring a blind hole costs more due to time to set-up block, once its setup on boring bar the other cylinders dont take much to bore thus the reason additional holes are cheaper..

 

[ib18]

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

ok, I called around and found the Ralph restoration in Stafford VA to hone and/or bore the 3 cylinders. Ralph is the owner, and I will know next week if honing is OK. He told me the bottom cylinder has aluminum on the wall. See picture of scratched bottom piston. It was seized in the bottom cylinder.

Ralph Restoration shop
57 Snowbird Lane
Stafford, VA 22554
Phone: (540) 659-3797

 

[oldman570]

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

If Ralph can remove the buildup of aluminum from the bore of the #3 hole he maybe able to just home it, and the others, without doing a over bore. If it is a mersoil block, it is chrome bored and he should be able to remove the buildup. Other wise it should be bored or sleeved to repair it. You can have Ralph mike the crank shaft bearing journals and see if they are still in spec, and replace those bearings also if need be. JMO
Oldman570

 

[Faztbullet]

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

This is a steel sleeved motor, Mercosil blocks are a boreable material sort of like a briggs/stratton block and chrome bore is just a plated aluminum hole...

 

[ib18]

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

My upcoming weekend projects are two:

1. Fix lower unit - Buy 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


2. Clean and rebuild my 3 carburetors, and replace all the carburetor gaskets. $90 for 3 -

One carburetor kit - Mercury Mariner Repair Carburetor Kit Complete Fit 70 to 90 HP 3 Cyl F76 | eBay.

 

[quicktach]

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

Since your shop will be over boring (10% ?) , do you have any thoughts about putting in WISECO pistons and rings ? They're not too much money but they're excellent and will stand the test of time..

 

[Faztbullet]

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

They're not too much money but they're excellent and will stand the test of time..

I myself am not a fan of WISECO pistons as they require a tad more clearance and extend break-in time as they need to go thru several thermal cycles to temper them.They work great in a worn out hole....

 

[ib18]

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

I will hear from Ralph early next week about my cylinders, so will check out the pistons later

 

[ib18]

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

Boy, $300 for the re-boring and honing the 3 cylinders. Ralph told me all 3 cylinders bent from overheating. All 3 cylinders are 15 over bore, so the previous owners did the re-boring job before. The top 2 only need honing, but the bottom cylinder needs re-bore to 30 over.

Clean ($60), measure ($35), bore/hone/straighten the bottom cylinder ($150), hone and straighten the top 2 cylinders ($55).

My total for this motor (parts alone) will probably be $1,000 - dang, hope it will run when i put it together.

1. cylinders - $300
2. 1 new piston (30 and over) - $100
3. Powerhead gaskets, rings, bearings - $500
4. 3 Carburetors gaskets kits - $50
5. Impeller kit - $50

 

[TD_Maker]

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

Again, I admire your ambition to start wrenching on your motor. You have quite a project going.

Your impeller kit will be a piece of cake for you. Take your time and take it apart, then just reverse the process. HOWEVER, check the lower unit for leaks before you put it on. See following:

The Lower Unit. Did you pop the drain screw yet? What color is the fluid? Amber color or even blackish color is good....this means no water is getting in the lower unit and you do not necessarily need a seal kit. Water and/or milky grey is no good, this means there is a leak somewhere. You will need to pressure test and/or vacuum test the lower unit to find the leak.

WORD OF WARNING about the Mercury Lower unit of this era....and it can be a pain in the butt. You will be tempted to unscrew the shift shaft housing to visually check the seal. When you lift this puppy off, you can easily pull the shift shaft out with it. DONT LET the shift shaft lift out. There is a little cam deep down inside of the gearcase (which is nearly impossible to align with the shift shaft) unless you want to pull the bearing housing....which is no fun with a motor of this age and vintage.

If your fluid is good color, and it is shifting smoothly in all gears, then just change the fluid, install a new impeller kit, and you are in business.

The Carb kits are pretty basic for this motor. I know you already have some Gunk Carb soak on hand (I saw it on your videos,) so I would go ahead and soak the carb bodies for awhile to loosen deposits. Get a couple cans of carb cleaner and some compressed air and go to it. All the carbs are identical, but make sure you mark Top-Middle-Bottom before disassembly and rebuild.

Other than this, I look forward to your updates. I rebuilt my motor just like this one. It is like a trip down memory lane for me.