1980 Mercury 200 Front half change to an 86 front half 2.4 L

[Welfare Racing]

I have an 80 200 Mercury #5464805
I have an 200 Mercury 86 front half with carbs (complete)

Can I put the front half on this engine?
and will it work correctly with out problems?

I need to have the electric enrichiner on this engine instead of a choke set up for my application

[ChrisCarsonMarine]

The front will bolt on I believe,I haven't done it,look at the crankcase mateing surfaces at the oil pump area to see if they will seal.The block from the 80 will have the inside bolt pattern on the heads,and no fingerports,The 81 225 was basically that block with a 7petal front,rated at the flywheel.The motor should run well,but won't make the power of a later finger ported motor,you'll need to work with the carb jets,Chris

[T-REX]

I alwayz leeve out tha dowl pins on tha block halfs and let tha crank line tha front half...I have had a couple that didn't turn free, and don't recomeend use'in it if tha crank don't turn free after torque'in tha front half on......Also have run into the end seel cap(bottom) lock'in up tha crank after use'in mismatched fronts....

other than sum oddity type stuff, tha front should juss be a swap!!...Performance differnce won't be enuff to tell(if any at all)...JMO

[Flatlander]

I just had that problem, where the the bottom cap was binding up the crank. If I loosened the bolts just a tad the crank would rotate ok. Is it ok run like that?

[Welfare Racing]

I am planning on using the carbs that came off of the 86 block (the 86 block has a hole in it from a piston) hence the swap questionwill I need to re jet seeing that I am using the 86 carbs?

[Flatlander]

The block I sent you is the newer style with a good horizontal front half. Is there some reason you don't want to bolt your carbs on that one? What carbs do you have 86' intake?

[Welfare Racing]

the one you sent me is already assembled....finished it saturday afternoon with new rings ect

[Flatlander]

Great, I didn't realize you were building two motors.

[Welfare Racing]

building 4

[tlwjkw]

I just had that problem, where the the bottom cap was binding up the crank. If I loosened the bolts just a tad the crank would rotate ok. Is it ok run like that?

I've run inta that a couple times. I removed tha snap ring at tha big bottom bearing and gave it a light smack (bearing) with a tool used to install a new bearing, used a NEW snap ring and tha bind went away (and stayed away after runnin' a while). Sometimes it only takes splittin' a fine red 'unt hair ta bring things back ta where its supposed ta be..............Maybe I've just been lucky, donno....

And NO, don't run it that way...............

[Flatlander]

Thanks, I'll give it a shot.

[ddantidwell]

if you dont use that front half, would you be willing to sell it? I have a 175 merc i'm looking to upgrade.

[Welfare Racing]

which front half? the 1980?

[T-REX]

Use tha jets on tha carbs U gunna use!!!....Even tho both motaz are 200 hp, each carbs have diffrent jet sizes for thier respective numbers....Mercury's better ideer!!!.....Exzample, My WH-31's(88' 200 2.4) haz .080/.082's....My wh-22's(225 2.4) haz .072/.074's......U put .072's in them wh-31s, and U have juss fried a 200 mota!!!!....IF, one ov thoze manifolds are X-drill'd, U have open'd a complete new can ov wormz...X-drilld manifold, step up 4 jet sizes(.008").....JMO

[Welfare Racing]

no cross drilling here all stock parts

[ChrisCarsonMarine]

Here's what is happening.The assembled height of the crank in the block is set by the lower main bearing and as the motor runs it slowly develops grooves in the block that are caused by the crank sealing rings wearing into the sealing surface on the block.When you change the crank there is a good likelihood the grooves won't line up perfectly,causing the bind,that's why the bind sometimes goes away with the lower cap loosened.It may wear itself in with no problem,I always remove the grooves from the block if I'm changing the crank,chris

[Flatlander]

well, now I don't know what to do.... The motor is completely assembled. When I torqued down the front half initially, the rotating assembly was smooth and quiet. It was not until I torqued the bottom cap to specs that the bind occurred. Some thoughts have been that the bottom cap is contacting the bearing and binding things up. The cure is to mill several thousandths off the inner face of the cap. I'm not sure I understand why the sealing ring surface would cause a bind "after" the bottom cap is torqued. It seems like it should have been tight without the cap installed.
By the way, I am looking forward to getting your reeds. I ported the cages last night and going to lap them today.

[ChrisCarsonMarine]

When you installed the crank the seal rings dropped into the wear area grooves cut by seal ring wear in the block from the previous crank,all was well untill you lifted the crank up in the block by pushing up with the bottom main cap...now binding the seal rings vertically.If it still turns but is just a little tight i would run it a couple minutes and see if it loosens up,if not,take it apart,chris

[Flatlander]

I don't mean to beat a dead horse.... but still trying to get a grasp on the problem. Your explanation was very good, the one thing I don't understand is how the bottom seal can actually lift the crank and cause binding. (unless I'm still not getting the picture). Since the seal is rubber, how can it put that much up force on the crank? oops, While I am typing this, I think I got it. Are you visualizing the crank in a vertical position? If so, why does the bottom cap put pressure on the bottom bearing? Shouldn't there be plenty of clearance between the inner face of the cap and bearing?
sorry for just not getting it....

[ChrisCarsonMarine]

Here ya go....look at your empty block,you see a machined pocket on the bottom that receives the bottom main bearing.This pocket is open on the bottom,untill the botton main cap is in place,then the outer race of the bottom main is held captive by the outer diameter,the upper block flange,and now the bolted in place bottom cap,which serves to lock the outer race in place as well as hold the seals.The lower main bearing,a robust ball bearing,sets the assembled crank height,locked in its machined pocket,held up in place by the bottom cap.If the seal rings on the crank arent at the exact same position as the previous crank seal rings,they may bind in the wear shoulders on the block where the seal ring outer edges ride,chris

[WATERWINGS]

I had a small chunk come out of my crank, (where the sealing rings are held) because of that same reason.

It was 1/2 the size of my pinky finger nail....but it caused BIG trouble.

[Flatlander]

Got It!!!!! I don't have the block in front of me so I was trying to picture in my mind (what's left of it!). What I didn't realize is that the bottom cap actually supports the outer race of the bottom main. Now it makes sense. Thanks for being patient and explaining the situation.

[boat2fast]

My experience doing automotive line-bores causes me to cringe everytime someone mentions mis-matched assembly halves. The parts are originally bolted together and machined as an assembly. When mismatched, it is not likely that every surface will line up perfectly or that bore sizes will be correct. Misaligned surfaces and loose/tight bearing bores do not allow seals and bearings to function properly at high speeds/loads. That is where 'binding' comes from. My 2cents...

[ChrisCarsonMarine]

Boat2fast,in some cases your correct,but not this time,I believe.In the manufacturing process regarding outboard blocks there are different methods employed by different makers.Generaly speaking,there are two standards of block machining,the one you're familiar with -alighnboring,a system involving casting a block in one piece,drilling,tapping,dowelling,the mounting flange area,then cutting the front from the back of the block,through the flange,lapping the surfaces,and bolting them securely together.Only then is the final machining of the end caps and main ways done,achieving a perfect fit and resulting in a matched crankcase set,front and back,replacing one or the other is asking for trouble,or at least should not be attempted blindly.
The other method( used in all v6 mercs I believe) is called "precision machined",a system where the front and back halves of the block are in fact machined to finished product separately,and become a matched set only after alignment dowelling pins are fitted by drilling the lined up( on a jig) front and back halves,resulting in a now matched set.This matching can be and often is disabled by the simple removal of the dowel pins.The halves are easy to line up at assymbly,the side to side takes care of itself,one has only to pay attention to the height of the front,make sure it's even with the back before tightening.I have removed dowel pins and mis-matched literally hundreds of blocks,I guess,over the years.Flatlanders binding is due to the seal rings,I'm confident,Chris

[Flatlander]

just a follow up, I went ahead an pulled the front half and then reinstalled the end caps and torqued to specs.. The crank turns smooth and easy. The front half does have small grooves where the seal rings ride. I am going to clean those up and temporarily reinstall the front half and check for binding. Will update later...

[boat2fast]

King Solomon wrote "By iron, iron itself is sharpened. So one man sharpens the face of another." Proverbs 27:17.
I have learned something new; Thanks Chris.

[ChrisCarsonMarine]

Thanks,you're welcome,brother...

[Flatlander]

real quick note, Thanks Chris and everyone else that helped me out with this problem. Sure enough, by removing the sealing ring grooves in the front half fixed the problem. Live and learn!
Thanks!!!

[WATERWINGS]

Did you bolt the two 1/2's together when you cleaned them up?

Or did you do them seperatly?

[Flatlander]

I only did the front half. That eliminated the bind completely.

[Flatlander]

I only did the front half. That eliminated the bind completely.

[WATERWINGS]

How did the two halves match at the split line?

[Flatlander]

where exactly?
at the top and bottom caps it was almost perfect.

[WATERWINGS]

Where the sealing lands meet at the split line between the front 1/2 and the block 1/2.