Rebuilding a chrome bore merc 200 hp 2.4?

[444]

Bought a boat that came with an early 80's merc 200hp. I understand this to be a 2.4 with chrome bores. Previous owner said 2cyls lost compression and the motor was disassembled and not touched since. I haven't looked at the block yet, but if the cylinders are bad, what are my options other than $$$ resleeving? I will have the block checked out by a machine shop before spending any money but for now I just want to know what my alternatives are.

If I understand correctly, the 175 and 200 in those years are both 2.4's, just with the 200 having the chrome bores and a different top end? Could I bore my 200 say .030 oversize to get past the chrome and use .030 over 175 pistons and rings to take it back to a typical cast bore motor?

If not, what are my other options to avoid having the chrome resleeving done? Use a block from a 175? Or is there a different block that all my 200hp/2.4 stuff will fit?

 

[CharlieB]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

If the chrome bore is hurt you can safely resleeve with conventional sleeves then use standard piston and rings. Piston weights are the same for chrome and steel bore engines.

 

[444]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Can the chrome bores be bored past the chrome so all I would have to do is plunk in a set of oversize pistons and conventional rings? Or are they made of a different material or chrome is too thick or?

If the bores are bad and the pistons are good, then I will definitely find out how much it'll cost to have the local machine shop sleeve the block.

Just for reference, were the 175's chrome bored as well? I really need to buy myself a factory service manual for this thing...

 

[CharlieB]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

You CANNOT bore a chrome bore motor UNLESS you RECHROME it. The liner is a different grade material and will not withstand wear of pistons or rings without the chrome finish.

Note: This is NOT chrome like you find on chrome parts, this is plasma coated and VERY hard.

The chrome bore liner is often bored out to paper-thin and peeled out of the block, then the block is bored to spec for the replacement standard cyl liner to be pressed into place. This new liner is the standard bore size, and can be over-bored for future rebuilds.

How bad is the original bore? Often a chrome bore will look terrible yet be so coated with transferred material from the piston that once cleaned off with muratic acid you may find the bore is still usable.

Never jump to conclusions without first cleaning so to be able to make a better inspection and measurement.

 

[444]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Thanks for the info on the chrome bore situation, that for sure answers some questions and reinforces some of my suspiscions. I don't have the boat at home right now and I haven't looked at the block myself yet, so I'm not jumping to conclusions by any means, just trying to figure out what my options are for rebuild IF the bores are bad. All I know is one cylinder(not 2, was mistaken) lost compression and the powerhead is now disassembled in pieces in boxes. If all the bores turn out to be usable, of course that would be my best case scenario, but in the mean time I just want to educate myself so I know what my options are if the bores are not salvageable.

If the 2.4 175hp blocks weren't chome bore, that could be an option instead of dealing with sleeving the chome bore block. What about 2.5 blocks? Will the 2.4 parts fit or is it an entirely different generation?

 

[444]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

bump.

 

[jigmister]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

I have a 1986 175 v6. it is chrome bore.
not sure if this helps you or not

 

[Faztbullet]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Yes they made chrome bore 175 blocks and if it needs more than 3 sleeves to repair replace it. Your parts can interchange with the 2.5 as long as you make sure you have correct main bearings and pistons(top/bottom guided). From what I heard US chrome does not use chrome anymore the new nicasil coating. If you have sleeved make sure that the repaired cylinder/s are rebored to 3.377 as these run hotter than the plated cylinders...

 

[444]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Did they make non-chrome 175hp 2.4 blocks or were they all chrome?

Faztbullet, so other than pistons and main bearings, everything else 2.4 will work with a 2.5 block? Electronics, intake, exhaust, etc etc etc?

 

[Faztbullet]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Did they make non-chrome 175hp 2.4 blocks

No... only steel sleeved 175 is the 2.0 liter. All your parts will work except exhaust divider plate heads and front intakke with can be made to work.

 

[444]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Okay, thanks for the info faztbullet, very helpful.

 

[trumanlake]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

Still have a 85' 200hp Merc that I rebuilt a few years back. Needed 2 holes sleeved. Rebuilt it myself, money wise not even close to what the "shops" wanted. Wasn't that complicated. Runs like a top.

 

[444]

Re: Rebuilding a chrome bore merc 200 hp 2.4?

I plan to get started on the motor in a month or so. I've built a couple big block v8's from scratch so I'm sure I'll be able to handle it. The condition of the block is going to be the determining factor.