1998 Mercury 200 EFI Mechanical Damage Rebuild

[Bigwrench]

As most of you know I experienced a breakdown last weekend and wanted to document my findings.
1998 Mercury 200EFI 2.5L Serial # 0G644422 roughly 500 hours on the engine.
  Let me emphasize the fact that I've never worked on a marine engine more than basic maintenance and pulling carbs and cleaning the bowls etc so the following is my learning curve and I want to share it with all of you. I've built many,  many engines over the last 28 years so I will be sharing some of that experience and how it relates to this situation. Where applicable I will also share my mistakes to show some things that can happen that you might not normally hear about.
  So sit down grab a cup of coffee or your favorite  and enjoy the ride.


                I approached this engine much like I would a car engine by performing a cranking compression test and inspecting the cylinders with a bore scope for any oddities or obvious damage.  Also I didn't go out of my way to perform a "by the book" compression test (holding the throttle plates open etc) because basically if I see damage or there's a large amount of difference in compression between the highest and lowest cylinder it doesn't matter in my book because it has to come apart and be addressed anyways (if that make sense )
All I'm looking for is an across the board compression reading to compare with each other and what state the cylinder walls are in (my biggest concern).
I started out by pulling all 6 plugs and marking them with a sharpie for location. 
On this engine the port side is even numbered 2,4,6 & Starboard side is odd numbered 1,3,5 with the top cylinders being 2&1 respectively.
Keep in mind at the time of the breakdown I used my  "hand test" on the cylinder heads which showed the port side to be the hottest to the touch which indicates the point of failure (high friction =heat) most times (at work I would use an infrared thermometer)
So here's a few photos of what I'm looking at , I used a basic bore scope that I have at home and had to take a picture of the screen so I could share.
  First thing I noticed was #4 plug was wiped clean compared to the other 5 this was my main point of failure and usually indicates water in the cylinder

Also important to note here's where I made my first Mistake, I did not Scope #6 cylinder and it came back and bit me in the rear end later on down the road (As you will see) #6 was my primary failure point
#1 plug what I would expect to see

#4 no carbon deposits (which would indicate normal combustion) this one is abnormal in my opinion


So now we start scoping the cylinders
A "normal" piston

A "normal" cylinder wall

#4 piston too clean for my liking also pay close attention to what appears to be oil residue mixed with water "white substance on the piston to the right of STD marking" 

#4 cylinder walls with significant scratching evident

Another shot #4


Compression readings
#2-60 psi.          #1-50 psi
#4-0 psi              #3-65 psi
#6-0 psi.             #5-65 psi

  I don't know what compression readings should be on a 2 stroke , I personally think all 6 are too low but know for a fact 0 is BAD lol.
Edit :
Compression Specifications at as follows
Fully Charged battery , throttle shutters wide open and cylinder block warm 110-135psi
Variance between cylinders should not exceed 15psi   
The point of failure was #4 obviously and since #6 was also 0 psi it makes me think of something that affects adjacent cylinders. If it was a car motor I would think head gasket ... But I know enough about these to know they are a totally different "critter" with Reed valves etc , So basically it's tear down time IMO. The cylinder walls are my biggest concern at this point if the scratches can't be "honed" then we're looking at machine shop work ($$$$) and an oversized piston rebuild kit , which appears to be the same price as STD piston kits. Also concerned with Head warp age due to heat. I can tear it down and get a better idea but also will need to purchase a factory shop manual for it before I attempt repairs if it's worth it.
    So there's a lot of choices to be made and I'm sure there are members here with much more knowledge on these "critters" than I have so lay it on me. What's your thoughts?
Am I in the ballpark or is it a waste of time to go further and just turn it into a anchor ?

[Mike Cork]

Sorry this happened to you but you are going to teach us a lot and I'm grateful for your time and cool tools thanks for these posts

[Bigwrench]

Sorry this happened to you but you are going to teach us a lot and I'm grateful for your time and cool tools thanks for these posts

Thanks Mike , I enjoy sharing the findings and also am somewhat out of my element with these motors so I'm curious to learn in the process also.
  I will probably run another compression test tonight with a different gauge set just to verify my readings and will probably add oil to the 2 cylinders reading 0 to see if it's piston rings at fault or something else. 

[Lee Smith]

considering the cost of a new powerhead, $2500 and up for remans, and including your expertise with rebuilding an engine, I would pull it down and rebuild.  Even if you have to get new heads, which I would expect, (don't think they could be straightened out at this age without clearance issues)  you would be way lower once done in $$.  Time is a different story, as you know, a rebuild will take some time, but hey, as the good mechanics say, it's just nuts and bolts, they come off, they go back on, 'nuttin too it' 

Get to work!  you go some buildin' to do!   

[Bigwrench]

considering the cost of a new powerhead, $2500 and up for remans, and including your expertise with rebuilding an engine, I would pull it down and rebuild.  Even if you have to get new heads, which I would expect, (don't think they could be straightened out at this age without clearance issues)  you would be way lower once done in $$.  Time is a different story, as you know, a rebuild will take some time, but hey, as the good mechanics say, it's just nuts and bolts, they come off, they go back on, 'nuttin too it' 

Get to work!  you go some buildin' to do!   

LOL Nuts & Bolts and Money 
Biggest factor now is money really and if I want to keep the boat .

     I found a new 2014 Optimax 200 for roughly $10K says its a CPO (?) with 1 year wty, the only thing about mine is we want dual consoles if we had that option our boat would get the full works front to back fully loaded for around $20k . If I fix this one then Sell it in a couple years I could buy the fully loaded used boat for roughly $35k. But whats it gonna be worth needing carpet and seat covers  even if the motor runs good ? Would love to slap a 225 or 250 ProXS on it LOL. But that's more HP than its rated for and to get the warranty a dealer would have to install it and of course they wouldn't do that ! I have about  2 1/2 months to get a boat running to take to Guntersville LOL 

[hughesjasonk]

How deep do you think the scratches are? do you think that you can hone it out then crosshatch with new rings or have to slide a bigger slug in there?

[Bigwrench]

I'm not sure yet , they may be superficial but to be sure if have to pull the head and measure the cylinder bore. That camera is just a. Basic bottom of the line one and it's not real clear. I could bring a better one home with a screen shot function and SD card or USB transfer capability but with the little one I just verified it has to come apart anyways. I think from merc there's only a .015" over piston kit IIRC when I looked on their catalog the other day using the Serial number search.

  Right now we are trying to decide where we are financially and if it's feasible for us to fix it   And trade it or trade it like it sits now. We are trying to get a few estimates now from a few different dealers on trade value.  There is no way at all we could afford a New one best we can tell right now. If my truck was paid for we woulda already drove one home lol.

Right now we have narrowed it down to :

2014 200hp Opti  $10k CPO (whatever that means)
$6-$8k used motor
2013 200 ProXS $9k
Rough estimate $2000 rebuild this one
09 208vx $33 vmax
09 Z520 $38 Opti
09 Z20 $34 Fully Loaded !! Etec
08 Z520.  $31 etec
07 Z21 $28 vmax
07 Z20 $36 etec
03 520  $21 etec


A lot depends on trade value now I think NADA is around $15 but assuming that's in great condition and not trade value.  lol
  Also have a call into my insurance company on the long shot that I may have coverage ?

Too many decision !!!

[hughesjasonk]

I can't be in your shoes right now. It would be bored out looking for ways to turbo or supercharge it by now lol. 0.015 i think will take care of those scratch from the pictures but who knows until you pop the head off.

[Bigwrench]

I can't be in your shoes right now. It would be bored out looking for ways to turbo or supercharge it by now lol. 0.015 i think will take care of those scratch from the pictures but who knows until you pop the head off.

I have a real nice graduated micrometer type hone that would work perfect with the wipers and everything , probably had it 15 years and used like 3 times lol

[hughesjasonk]

Those are really really nice that way you can gradually increase the bore. I broke mine a number of years ago so now I just use darton east to do all my machining

[Bigwrench]

I also just found the Mercury Shop Manual Online for free in PDF format  
For anyone who might need one now or in the future this would be a good file to grab and store on your computer or phone




It's on now lol

[hughesjasonk]

Lmao

[analfisherman]

CPO means Certified Pre-Owned.
Usually they are usually backed by the manufacturer, and are typically just a few years old with low HRs.

Ask around your shop, I'm sure they have or have had CPO cars for sale.

Usually it's a warranty exchange and the motors are rebuilt based on manufacturers specifications.
With manufacturer backing the rebuilt with some kind of warranty.

[Bigwrench]

That makes perfect sense then ! Thank you brother ! On that one they gave 1 year warranty coverage
Yeah we have certified pre owned also on our vehicles. Don't know why it didn't click.

[merc1997]

bigwrench, i am thinking that your engine compression should run110 psi on the 98 year model.  if i remember the last year of high compression on the efi was the '96 model.  with that many cylinders down, you will at least have to take the heads off to see what is going on.  with reeds, you also need to do a leak down test.  you can lose a lot of compression with bad reeds.

did the engine lock up??  sometimes powerhead failure begins with the lower unit.  you need to check it also.  if something in the lower unit is binding, it can cause the power head to shoot craps.  if the crank and rods are good and not damaged, i would just rebuild what you have.  if the problem started with fuel starvation, then you would also need to have your computer redone as it controls fuel delivery, and that is a major source of engine failure on efi's.

bo

[Bigwrench]

bigwrench, i am thinking that your engine compression should run110 psi on the 98 year model.  if i remember the last year of high compression on the efi was the '96 model.  with that many cylinders down, you will at least have to take the heads off to see what is going on.  with reeds, you also need to do a leak down test.  you can lose a lot of compression with bad reeds.

did the engine lock up??  sometimes powerhead failure begins with the lower unit.  you need to check it also.  if something in the lower unit is binding, it can cause the power head to shoot craps.  if the crank and rods are good and not damaged, i would just rebuild what you have.  if the problem started with fuel starvation, then you would also need to have your computer redone as it controls fuel delivery, and that is a major source of engine failure on efi's.

bo

Your dead nuts on Bo its actually supposed to be 110-135psi from the service manual, that I found online last night for FREE ! That Sucker is 797 pages long !! But I now have everything I need to tear it down and start diagnosing !
  I do plan on draining the lower unit oil and checking that for sure, I was told by a Marine tech that with water in that cylinder it is most likely a failure of the exhaust gasket or exhaust divider plate. But I really don't know for sure. I will start tear down this weekend hopefully once I get the garage cleaned out and will be looking at everything I can because I obviously want to make sure whatever caused it to happen is fixed too. I am gonna contact a couple Mercury guys online and see if they have any suggestions.

[Bud Kennedy]

This Thread is going to be a classic for years to come.  All of us are going to learn a whole bunch even though it sure brings back some nightmare memories.

[Bigwrench]

Here's a little update on this situation. The damage may be covered under my insurance plan , small chance but a possibility and currently have a $0 deductible. Only catch is it has to be torn down at a dealer. Dealer quote for diagnostics is $125 max , if covered no out of pocket expense . So for $125 I'll get a solid diagnosis by a certified marine mechanic and an estimate on repairs. 

  I was also told we could look at a few boats on the lot and we will get a trade value on ours also. But not to "get my hopes up" so that's a start lol. Stay tuned. 

[hughesjasonk]

It's better than nothing

[Bigwrench]

It's better than nothing

Absolutely and I've been studying up on this motor so
Much lately My brain is fried lol

Looks like it could be a few things allowing water in the cylinder not to mention a crack in the block between 4&6. I'll leave this to the ones with the knowledge and then make a decision once an estimate is made and a trade value as well. Then we can look at the whole scenario with solid dollar figures and go from there. To be honest even if the insurance somehow covers it we were gonna trade it soon anyways , was going for one or two more years though lol 

[hughesjasonk]

I hope they actually find what's wrong with it.

Don't get too complicated with it a motor is a motor. They are all differently the same

[Bigwrench]

Well she is now sitting at Bunch Marine in Harriman TN. Was a good drive for me and momma and we made a day out of it. We looked at a z520 and a Z20 , if she woulda stayed home one of em woulda been coming home with me lol

[Oldfart9999]

I would look for cracks between 4 & 6, if none then check how flat the heads are and if they are warped if there is enough to shave them before going any farther. Did one or 2 engines on sleds in my younger days. If it becomes a matter of oversize slugs see if there is enough metal in the jugs to bore, pistons can come from other than OEM, Wiseco comes to mind.
Rodney

[hughesjasonk]

Well she is now sitting at Bunch Marine in Harriman TN. Was a good drive for me and momma and we made a day out of it. We looked at a z520 and a Z20 , if she woulda stayed home one of em woulda been coming home with me lol

Probably why she went

[Bigwrench]

Probably why she went

Lol Yep !