Merc 2.4 Chrome #2 cylinder sick for Rex and others

[rvaha]

I had the boat out this weekend pulling tubes and was loaded with people (11 in all). Motor had been OK, but when it was maximum loaded it started to slow down. RPM's at the time were around 4K. This is on a heavy boat, so I don't have it set up for speed. It seldom sees more than 5k rpm at any time, and for short intervals.

Block is a 2.4 - I think a 1991 replacement block with all 6 bores chrome. Compression on all holes had been 136-145 (heads been cut) Timing at 25 degrees. 1 inch spacer. Carbs are WH-46's with standard jetting (I think 2 and 5 have 82's, and the rest have 80's)

Anyway, #2 hole has bad compression. Removed the head and the piston has a small hole at bottom. Ring still intact. Motor still runs, although not well.

The cylinder has some scratching and a small place where the chrome was gouged into the aluminum. The intakes and exhaust ports look OK. The cylinder has some egg shape - a little over 10 thousands.

My question -
I understand that it probably should be pulled apart and resleaved and/or rechromed. However, time and money don't permit as I'd like for the kids to enjoy the summer on it. So - I have additonal pistons - Can I pull the reeds and pull the rod and pistion without splitting the block? I think I've read where it can be done but can be tricky getting the rod bolts lined up. Also, is there anyway I can reduce the amount of egg shape. I placed a C clamp from top to bottom on the cylinder and have reduced it a bit. It is longer in that direction. Will this work? Do I need to add heat?? If so how much??

The scratching and gouging I know will also affect the performance. I didn't see any of this around the exhaust or intake. Seems like I saw Rex post that "as long as water is not coming thru the gouge, it will be OK"

Obviously, this cylinder would underperform the others. This isn't a race boat, so I don't care about that. Just want to get it back and running asap. I also know that it will need steel rings for the Chrome bore.

Is all of this possible?? Again, I know this isn't the optimal situation.

Oh - I'm guessing that perhaps #2 may have gotten lean. Haven't read the plugs. (My fault). Last, water pressure good (14 lbs). Both pyros around 1100 - but not sure when this happened!!!

As always, thanks a bunch for the help on the site!

Rick - (540) 521-5211

[WATERWINGS]

interested to hear the answers....I sometimes run a "less than perfect' motor myself.....and I have changed pistons twice without pulling the powerhead....no problems with that....

[kb5050]

you have to put everything in from the cylinder side (rod, cap and bearing) make SURE rod cap is oriented to rod correctly. rod bolts in from reed side with long extension. Is aluminum stuck to chrome or scratched thru it? If it's smeared on the chrome you can remove it with muratic acid on a q-tip, but don't let the acid get anywhere but the aluminum you want to remove.

[HStream1]

Kb gave you the correct answer. But why do you have a engine set to 25* with 140 compression and a spacer plate pulling Tubes and loaded with 11 people on a heavy Boat.???????

I'm not trying to bust your chops and understand your wanting to stay on the water this season, but Hello??? And you need to get that bore straighter than .010 ths.

I know Jay Smith, Ruck and a few others have a tool that straightens and rounds bores. But I believe you have to break the block from the front half.

I would say you need to retard timing some, loose compression some if you are going to continue to do like you described.

Good luck though, it's no fun when you can't go out. But even less fun when you have to be towed in because of a rod through the side of your block.

just my 02

[rvaha]

Guys - thanks for the answers. I agree with all that's said. There is some aluminum on the cylinder. I did remove some with muratic acid. Also, there is a small gpuge thru the chrome into the aluminum, and some scratches. I'll pull the piston and have a better look. For Bud, I'll probably leave the compression as is, but retard the timing a bit as well as move the jets up a bit. I agree that it needs to be better than 10thousands off.

As I mentioned, I do have some spare pistons. Pretty sure the rings are for steel bore. Not sure how to tell the difference between the rings I need for chrome (steel rings), and for a steel bore (chrome). I think I read somewhere that chrome bore rings were black - or is that just a manufacture detail. I'll likely order new rings and head gaskets so it probably doesn't matter.

Last, for Bud and all - I've done the rod thru the block once and got towed by the fireboat. My son thought it was a blast. Got some spare engine parts - some with holes in them - laying around. But who on this site doesn't have some fried aluminum???:cheers:

[HStream1]

Here's one for ya. Great attitude you have there my friend.!!!


http://i465.photobucket.com/albums/rr18/jbcincnc/Piston-1.jpg

[rvaha]

Ouch - looks like a tow and painful:eek:

I just pulled the reeds. The top reeds (cyl 1 and 2) have water around them and in the cylinders. Looks like a grey,gooey sludge. Also have a lesser amount, but still some, on the middle reeds.

I've only pulled the port head. I noticed that the metal ring on the middle of the gasket on all cylinders seems to be compromised. When I bought the engine, the person only had head gaskets for a 2.5. He said they would work - but I wonder if because a 2.5 cylinder is bigger that the wrong gasket could have compromised the seal around the piston. I haven't pulled the starboard side, but bet that head gasket has similar issues. I'll be installing new 1 piece 2.4 head gaskets for sure.

I've corrected the egg shape some (withing 6 thousands) with a C Clamp. However, it does spring back some - not all - when taking the clamp off. How much heat would I need to get the cylinder hot enough to hold the correction that the C Clamp provides?

Pulling the piston from the front went well.

All thoughts are welcome. Just wonder if some of the water in the top 4 cylinders was caused by the wrong head gaskets??????

Thanks!!

[jody504]

They do make a tool to get the egg out You can take a old piston and cut it in halve put a bolt inside of the piston and use it to push the wall out push it .003 pass where you want it and it should be close to round after. I would put 2.4 gaskets back on it. Run it on the hose are in the water after pull the head after if everything looks good Have fun this summer. As long as the chrome don't come out it should be O.K.

[TEXAS20225]

i remember them days oh so long ago when i had ever so much more energy then money ;)i personally have had zero luck with a cylinder that went own and alum was stuck on the sleeve even when i had a boring bar cut a smidge out of it to clean it up they went down shortly after reassembled

[rvaha]

Jody,

Thanks for the idea. Just so happens I do have extra pistons!! :eek: Never thought of that. I have corrected some of the egg shape with a C Clamp on the front of the cylinder. It does return somewhat when I release. Do you heat the Cyclinder while performing your method of making the cylinder round to make the cylinder retain the shape?

Thanks all!

[jody504]

This is not the right way by all means But I have seen on more then one time in the parking lot in the middle of the night where you do what you have to do to make it work. You don't have to heat it just push it more on the smaller part of the egg.Push it past 0 then when you release it it should come back almost to zero. I have seen the pin come out and have A line from top to halve way down run. Like I said this is not the best way but what do you have to lose. You may have to put a sleve if it don't work but sound like thats what needs to be done now if you don't try. I have a friend that took many of 1st at the races with a not so scare free chrome block.

[rvaha]

Jody, thanks for the detailed explaination. Good to know I don't have to buy an acetylene torch. I did try MAP gas - but not hot enough to matter. I'll be cutting a piston in two asap and do as you said. Like I mentioned, I'm not racing - just want it to run in the 4-5k rpm range. BTW - although it doesn't matter,I was only at around half throttle when this happened. I very seldom run full throttle except when taking off.

[rvaha]

OK - took Jody's suggestion and cut the old piston in half and inserted a 1/2 diameter fine thread bolt. I remeasured the bore before inserting the piston and bolt and it was at least 15 thousands out of round. I was able to get the cylinder back under 6 thousands thru a combination of Jody's piston method and clamping at various points on the front of the cylinder. I did have to use a lot of pressure on both methods. My guess is that since this is a chrome bore, when you release the pressure it wants to go back where it started, while a steel bore may tend to hold shape after pressure is applied.

Also, I cleaned up the cylinder with alcohol and muratic acid, then alcohol, and put in JB Weld to fill the small gouge and scratches. I put towels in the ports to keep the excess debris from getting into the engine. Did a light honing to get all of the excess JB weld off. CLeaned good and lightly oiled the cylinder. It came out better than I thought. Very smooth.


Installed new 2.4 gaskets on both sides. This cylinder (#2) now has 130lbs compression. Ran motor for a while on muffs. Compression went up just a bit. I guess time will tell how things last. I know this method probably gives engine builders nausea!


One last thing. I had around 145lbs compression on all starboard cylinders and 140lbs compression on bottom 2 port cylinders before I pulled the heads. They are all now down about 10lbs on all - roughly 130 to 135lbs on all cylinders. The only change I made was going from the original 2.5 head gaskets to new 2.4 head gaskets. The fire ring is of course slightly smaller. I would have thought the 2.4 gasket might have a little higher compression since the fire ring is tighter, but also wonder if the 2.5 gasket and larger firering allowed for a little tighter head to block measurement since it was perhaps distorted due to the wrong size. Both gaskets said they were 1.2 mm thick. Any ideas on this?? Used same gauge and location (no elevation change).

Last, I upped the jet size .02 on all cylinders. I'll test once on the water.

Comments welcome. Thanks Rick

[WATERWINGS]

Let us know if the JB Weld is still there next time you pull the heads.....(not trying to be smart azz....I just want to know)

[delawarerick]

I have one 5 out and it has run like this and I say it will run till I replace it 6 seasons so far. I have seen crap pieces used and last as long as new. Dave S on here knows some real good tricks. Budget boating 101:D. Rick

[davemvegas]

if you are going to load a lot of people in boat and pull a tube you would work the motor a lot less if you drop down a couple sizes in prop pitch. a motor lugging a load at 4000rpms builds cylinder temp a lot more then when you let the rpms do the work.

[outasite]

I don't know much about the carbs your using,but sometimes carbs have a midrange jet or transition jet.Your top end jets may not be working at their max at 4000 rpm.You mite be going lean in the midrange just a thought.

[rvaha]

Thanks guys - John, I'll let you know about the JB weld. It did OK on the muffs. Running is another thing. Picked the idea off of a tractor site. Figured what have I to loose. Dave, running a 19 pitch with a 2 to 1 lower. It will do 6k rpm plus even with the load. I think the load did lean it out. Outasite - they are WH46's Had 96's in all of the vents. I think the factory spec is no vents in #2 and #5. I removed both of those vents, and as mentioned, increased each main .02. I bet your right though - I wonder if I had the vents out in #2 and #5 if I'd be writing this now!

Any thoughts on the compression change that I mentioned on my previous post on all cylinders?

Thanks again. I'll have it out this weekend - hopefully not behind a towboat!:eek:

[WATERWINGS]

I think that I pulled ALL the vent jets out of mine....

[rvaha]

Thanks John - may do that. I'm guessing that pulling the jets makes it slightly richer. Might hurt gas consumption a bit, but protecting the engine is more important. Have others pulled the vent jets? Good or bad experience?

[WATERWINGS]

I had hotter EGT readings around 5000 RPM's...I was told that would cool them down at that range....If I remember right, it did cool some...

[rvaha]

UPDATE:

I actually got the engine fixed a couple of months ago. Haven"t had the chance to write the results. Anyway, before the measurements the egg-shape was over 25 thousands and as mentioned a few scratches and 1 gouge. I cut a piston in half and used it and a "C" clamp to "round" the hole. I was able to squeeze the cylinder from top to bottom with the "C" clamp by gripping right on the edge of the cylinder. I had to use a lot of pressure, both on the C Clamp and cut-in-half piston. I'm guessing because it's a chrome bore that it would not hold the position as well as a steel bore.

I used myratic acid and then acetone to completely clean the cylinder. Then I used a decent amount of JB weld to fill all bad places. Then used a hone to remove excess. Finished off with Scotchbright.

Installed a new piston and put back together. Ran compression. Only 70lbs! Ouch. Took head apart and remeasured bore. Sqeezed and pressed again. Got within 6 thousands. Put back together. Now have 145lbs.

Have ran it multiple weekends. I rechecked the other day. Compression between 145 and 150 on all cylinders - including this one.

John had asked if the JB Weld held. My guess is yes. Compression is the same now as then. I hate to pull the heads and possibly ruin a good thing.

Anyway, thought I would let the gang know my results. Salvaged a boating season for sure!