Merc 888 rebuild project

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Here's some background on this project, and I have a few technical questions, and I'm sure more will pop up down the road. This boat was a 19ft. 84 Chapparal that was left to me in an estate. It looks like it was repowered with a 72 Merc 888. This thing was junk, and I planned on parting it out, using it to help finish the boat I want to keep, which is sitting right next to this one and will probably end up in anther thread. Anywho, I pulled the motor and drive, which were in decent shape. Motor was stuck, badly, but the drive and transom assembly are in good shape. I did a little research and found that the whole running rebuilt engine is worth a lot more than the sum of its parts, so I decided to rebuild it. I'm wondering if I should have just parted it out. Anyway, here's where I am:

  • I gutted the motor, block tested good, I rebored and sleeved a few cylinders. Cleaned out the rust in the cooling jacket. This thing had never been touched. All the rod bearings, etc, had the original ford date stamps from 1972 on them, so everything was original inside the block, and in relatively good condition, aside from the 2 rusty cylinders.
  • New pistons on the old connecting rods, new rings, etc.
  • cleaning and powder coating the old pulleys, oil pan, etc. (that's been fun, and looks GREAT!)

I bought a rebuild kit for a regular 302 motor (rod bearings, main bearings, rings, oil pump, gaskets, timing set, cam bearings, , figuring that the base of the motor would be a regular 302 with the peripherals designed for marine use. I think I'm finding out that the differences go deeper than I thought.) I put the main bearings and the crank in without much issue. So far so good. Put the new oversize pistons on the connecting rods, rings and install. Still going good. I put the rod bearings on and bolted them onto the crank. (The Seloc manual calls for the bolts to be tightened past the failure point of the rod bolts, so I had to replace the bolts after they all stretched and a few snapped.) I tightened the bolts to spec, and after tightening only 2 caps, the engine won't turn. At. All. There's no way this is right. With all 8 tight, this thing should turn over with minimal effort. I took it out, one of the caps is cracked, and none of the rods go back together without a fight. I'm thinking the 302 bearings may have stretched or distorted the rods, and that the Merc bearings are not the same as the 302 bearings.

This creates 2 questions:

First, Are the Merc bearings the same as the regular 302 bearings?

Second, I obviously have to replace at least some of the connecting rods, which are no longer made by Merc. There are a handful of used ones available, but they are incredibly expensive and will most likely require work if I get them. Can I get a set of racing-quality connecting rods and replace the set? A set of 8 aftermarket racing rods is still about half the cost of Merc rods, and I think they might be stronger than heavy-duty cast of yore. My head says that as long as the dimensions are the same, it should work fine. Since no one lists a replacement rod, I might have no choice. If I do that, I would assume that the regular 302 bearings will fit better, too.

Lastly, moving forward, is there anything else I need to look out for using 302 replacement parts? I think I need to get a Merc head and intake gasket, but the rest should be fine.
 
Last edited:

spdracr39

Lieutenant Junior Grade
Joined
Aug 30, 2010
Messages
1,238
Re: Merc 888 rebuild project

you didn't get the bearing caps reversed or mixed up did you?
 

funk6294

Petty Officer 1st Class
Joined
Apr 26, 2009
Messages
294
Re: Merc 888 rebuild project

Couple of things come to mind. First, as stated before are you sure the caps are on the right way? You didn't swap caps and rods, right? Provided all of that is correct I would then check to make sure you didn't end up with undersized bearings (if the crank was not turned) or the wrong undersize bearing (if the crank was turned.

On to the connecting rods. I would simply look for a set of used rods out of a 302. Also what torque value did the manual list? If the rod bolt values were off, I would be suspect of the other torque values listed as well. Might be worth checking some other sources to verify values.
 
Last edited:

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Re: Merc 888 rebuild project

you didn't get the bearing caps reversed or mixed up did you?

Doubtful, but not impossible. There are a few that have no marks on them at all. Typically, the matches have numbers stamped on them, and you just match the numbers and the numbers face the bottom of the motor when you put them in. However, several of them don't have numbers on them. :confused: Anyway, I kept them in order when I took them out, so it's not likely.
 

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Re: Merc 888 rebuild project

Couple of things come to mind. First, as stated before are you sure the caps are on the right way? You didn't swap caps and rods, right? Provided all of that is correct I would then check to make sure you didn't end up with undersized bearings (if the crank was not turned) or the wrong undersize bearing (if the crank was turned.

It had the original bearings in it, complete with the date stamps from 1972. I doubt it was turned. Even if it was, wouldn't standard bearings be the thinnest bearings, resulting in the rods being too loose?

On to the connecting rods. I would simply look for a set of used rods out of a 302. Also what torque value did the manual list? If the rod bolt values were off, I would be suspect of the other torque values listed as well. Might be worth checking some other sources to verify values.

That's what my head is telling me to do, but I'm hoping for a little coaching before I pull the trigger. I'm leaning toward heavier-duty racing rods, though, as Merc says regular rods aren't designed to handle low-end torque. My thought is that stronger rods designed for high RPMs will also handle low-end torque. However I could be wrong, and that's why I'm here.
 

Fleetwin

Lieutenant Junior Grade
Joined
Nov 23, 2011
Messages
1,141
Re: Merc 888 rebuild project

When Merc. "Marinized" that engine, all they did was add marine cooling and marine accessories (alternator, carb., etc.).

Ford built the engine with a different camshaft and marine core plugs-that's it.

Don't over think it.

You can get a lot more than 188 out of the engine with minor mod's such as: Manifold, carb., head work.
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: Merc 888 rebuild project

I suspect you got bearings for an engine with a remanufactured crank, that is not standard size. The bearings are thicker to make the clearance. They will be stamped accordingly - e.g. "U/S" for undersize and then a number like .010

Regardless, You need to get a book like David Vizard's or similar that walks you through how to use plastigage, and how to use precision measuring tools to measure the parts before assembly.

Who honed the cylinders? Wherever that work was done can measure your crank and get you the right bearings. Did anyone pressure test the block?

Rust in 2 cylinders is usually a symptom pointing to the root cause of the seizure.
 
Last edited:

grewvin1

Petty Officer 2nd Class
Joined
Apr 2, 2012
Messages
189
Re: Merc 888 rebuild project

Ran a 1972 302 for 28yrs in my Grew. it's just a 5L truck engine with forged rods and crank with a different cam for marine as noted by Fleetwin. I'd install the crank and hand turn then start to add rods and pistons one at a time turning each time I add a rod and piston. Confirm torque values on the web for reqular ford engine specs your book may have a typo.
 

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Re: Merc 888 rebuild project

When Merc. "Marinized" that engine, all they did was add marine cooling and marine accessories (alternator, carb., etc.).

Ford built the engine with a different camshaft and marine core plugs-that's it.

I put the same cam back in, and it set firm with the new bearings. Not worried there.

Don't over think it.

You can get a lot more than 188 out of the engine with minor mod's such as: Manifold, carb., head work.

I'm not trying to get HP out of it, I'm just trying to get it running.
 

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Re: Merc 888 rebuild project

Ran a 1972 302 for 28yrs in my Grew. it's just a 5L truck engine with forged rods and crank with a different cam for marine as noted by Fleetwin. I'd install the crank and hand turn then start to add rods and pistons one at a time turning each time I add a rod and piston. Confirm torque values on the web for reqular ford engine specs your book may have a typo.

That's what I was doing, and it stopped turning after a few rods were tightened. :blue: They turn fine when only hand-tight.
 

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Re: Merc 888 rebuild project

I suspect you got bearings for an engine with a remanufactured crank, that is not standard size. The bearings are thicker to make the clearance. They will be stamped accordingly - e.g. "O/S" for oversize and then a number like .010

They have STD stamped on them.

Regardless, You need to get a book like David Vizard's or similar that walks you through how to use plastigage, and how to use precision measuring tools to measure the parts before assembly.

Who honed the cylinders? Wherever that work was done can measure your crank and get you the right bearings. Did anyone pressure test the block?

I had it tested and bored at a local machine shop. Sleeved the really rusty cylinder and bored them all .030 over.

Rust in 2 cylinders is usually a symptom pointing to the root cause of the seizure.

I think the rust came from the valves that were left open over time. There are 2 other valves that need to be reseated, and they are at the shop now.
 

DJ Jaws

Seaman Apprentice
Joined
Nov 6, 2008
Messages
43
Re: Merc 888 rebuild project

SO here's an update. $325 later and lots of research, I found a set of rod bearings from Mercruiser. Had a few delays due to weather, illness, and a death in the family. These were discontinued long ago, but thinking that they may be different than the ones I had, I spent the small fortune to get them. I opened the box and took a micrometer to them, and they were identical to my mustang rod bearings. Back they are going. I found a used set of mustang connecting rods that had the same casting number and everything. Mercruiser discontinued them long ago too. I found out why, since these are also readily available on the automotive market despite what Mercruiser says.

Anyway, I took out the old connecting rods that weren't marked and replaced them with the used connecting rods. I have seven cylinders back together, and the engine turns. It's tight, but it turns, which is about right in my experience. Naturally, I broke a piston changing the connecting rods, so the eighth cylinder isn't together yet. Story of my life. However, it seems that the connecting rods were the problem all along. Had I made sure the marks were all present when I took them apart, and a simple stamp to the ones that weren't, it would have saved me a pile of money and a small pile of gray hair. It is weird that some came out marked and others had no marks on them at all. PEBKAC error all along!
 
Last edited:
Top