Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, ideas?

[pooh_b_21632]

I am going to weigh my options here in my opinion we should put in four new pistons the $500-700 or so to do it is less than another used engine (and less than someone elses headaches IMO) Hubby does not want to rebuild he wants to purchase another used engine.

We have a 1990 120lx90b long shaft that the number three piston came apart on. The damage was quick leaving one tiny mark on the number 2 cylinder wall which still had 125lbs of compression at the time we discovered the damage. Boat still ran with the damaged piston but had a slight misfire (loss of compression). I feel we could remove the flywheel, open the crankcase, replace all four pistons, and hone the number 2 cylinder with the block attached to the leg (if it needs to come off the leg he will not do it) or maybe even just leave it alone it did have good compression after all the way it was.

Hubbys concerns:

1. how to get the piston off the rod
2. how to keep the bearings in while reconnecting the rod to the crank
3. how to time the engine and what to be careful of while the flywheel is off the engine (He doesn't want to spend the money for new pistons/rings and gaskets then its out of time and the pistons hit the head) causing more damage

I am willing to do half or more of the work myself but I can only do what I know how to do.

Step by step instuctions would be great I have a manual but its a bit confusing and all over the place.

As of now the head is off, the carbs and reeds are out, and the number three piston is out. Tonight I plan to remove the other three pistons and see what I have as far as damage.


The guy I buy my parts from told me he knows we can do it and it would be stupid to not put new pistons in it, as much time and money I have spent working on it so far.


So I can spend around $1000 for a motor with potentially the same problem, or I can spend $1000 to fix my motor that I know has a good lower unit and everything but the pistons looks good to me.

 

[bentle]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Could you get by with just honing and new pistons rings?I have read other threads where this can be done as long as the piston wall doesn't have a whole lot of
Damage.

 

[Frank Acampora]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Well, it is a difficult call: On a 4 cylinder engine with only two pistons damaged, it is not really necessary to replace all four. The engine will be perfectly happy with two new pistons and two old ones. These are NOT like automobile engines. HOWEVER: If it would set your mind easier, then by all means spend the money to replace all four.

Honing WILL remove very light scoring and compression will not suffer. However, if the scoring is deeper, then a rebore is necessary.

Tolerance for wear, out of round, and taper of cylinders is only .002 (two thousands) for Force engines. OMC has a tolerance of .005--go figure.

At any rate, piston pins can be hammered out or you can buy a small press from Harbor Freight or Tractor Supply ETC for around 60 bucks. Wiseco aftermarket pistons come complete with rings and wrist pins AND the wrist pins are held in by clips, not pressed in like stock.

Roller bearings are held in by grease while assembling the rods. Rod caps are matched and must go on their respective rod in the correct orientation.

Timing will not affect piston clearance--they always clear the head. It is not like valves on a zreo clearance auto engine where the valves will bend if the timing chain/belt breaks.

It is really not a difficult job and if a cylinder does not need to be overbored, the pistons can be replaced with the block mounted on the leg.

After rebuilding, read the sticky: FAQs Synchonizing timing and carbs.

Your husband is thinking with the Y chromosome. You happen to be more correct: You can repair the engine relatively inexpensively and know what you have. Every used outboard "ran when it was put away" and you really don't know what you are getting--especially for small amounts like 1-2,000 bucks. Caveat Emptor!

And by the way: The engine in the avatar has had only #3 piston replaced with a light honing. It runs very happily at 45 MPH on that boat.

 

[jerryjerry05]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Post pics of the bad!!CLOSE_UP and CLEAR.If you can feel a lump with your fingernail(cylinder wall) then you might need a rebore.
The pistons should have NO damage if you plan on re-using.Pics!!.
Pistons won't hit the head at all.Unless it comes loose.
They sell assembly grease that melts quick after it's been started.That will hold in the bearings while you assemble.
Make sure that you count them and make sure they go back in.
Don't use a magnet unless you really have to.Use a VERY weak one if needed.
The bearings can be slightly magnitized and pick up shavings.
Will need a press to do the connecting rods.

 

[tater76]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Frank and Jerry are right, it may be a preference or difficult call. You know where I stand on your motor though, and I think Frank is thinking similarly. I don't like to spend money on things that are serviceable or working already. If #2 piston has damage that will harm the cylinder replace it. If the cylinder just needs to be honed, do it. It sounds like you have a decent running motor, so why mess with the whole thing and not the known issue?

4 new pistons will cost approximately $400, then gaskets, possibly rings if the pistons didn't have them included. This will add up quick, so when you weigh buying rings for all 4, renting a hone, and a few new gaskets......?? but I'm a self proclaimed cheapskate, so take my opinion/advice not as gospel but as something to think about.

 

[pooh_b_21632]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Well we pulled the other three pistons when my husband got home from work. They are all trash (not obvious from the top though). Its raining here in Maryland right now but I will try to get pictures tomorrow. It was obviously ran hot (and I mean HOT even the crank has heat discoloration) at one point or another ( I am assuming right before the previous owner sold it to me ). Anyway the number 1 and 2 cylinders have a very light "bump" at about 11 o'clock on each one. I think it can be honed with a ball hone though. I was wondering If I could take the lower cowl off without much difficulty? also two of the roller bearings from the number 4 piston are missing I cant find them anywhere inside, going to look again tomorrow but it started raining on me. Still not sure what I want to do, Hubby is a bit "over cautious" when it comes to engines (we have over 7,000 in his rotating assembly alone on his camaro). He likes things to be done right. He thinks replacing just the pistons is "half assing it" and that its asking for more trouble down the road. I mean if I had 10,000 laying around I would go buy a new one

 

[jason32038]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

I had a cylinder bored out and the other 2 honed and only costed 100+tax. Picked up brand new wiseco piston on ebay for $70 The thing is finding somewill who will or wants to machine it. When I took mine in they were iffy about the whole thing. I finally got my powerhead back 4 months later LOL.

 

[tater76]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Let me guess, pulled the pistons out and the rings were cracked/broken/stuck? By "bump" you mean a scratch running the length of the cyilinder right? I say this because I have seen "bumps" in cylinders that are actually divots from the piston being driven at an angle into the cylinder. Pictures Please

 

[pooh_b_21632]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Ill get pictures tomorrow. On the pistons, no I mean half the piston on each on the part between where the ring goes the rim that holds them apart is broken and a chunk missing. I cant believe it ran like that let alone had good compression on three cylinders. On the cylinders its like a thin v shaped heat scorch mark that you can feel its slightly raised and discolored I may be able to clean it up and its just burnt on carbon build up will post pictures tomorrow if its not raining.

 

[Frank Acampora]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

You are almost local to me. Maybe an hour and a half to 2 hours away. See my private message to you.

 

[pooh_b_21632]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Here is a picture of one of the pistons sorry its a bad picture I cant seem to get a good picture. Cant get a picture of the cyllinder at all. I need a new camera

 

[jerryjerry05]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Your camera have a closeup mode?
I used Jet Machine Shop Mountain Rd. Pasadena,Md.They were good and fast and won't jerk you around.
ANY defects or when in doubt throw it out.
You need to find the bearings.They will work themselfs into the crank and then you will need another rebuild.

 

[pooh_b_21632]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

I found the other two bearings last night (reached in through the cylinder and felt over to the side kinda behind the cylinder to the right there is like a groove in there and low and behold there they were. So my husband decided he would help me if I needed him to but the rebuild is up to me. So last night he brought me a 3 stone lisle hone from work and I honed all four cylinders (getting four new pistons and rings anyway why hone just the 2 with a bump?). So anyway the bumps are gone cylinders clean. Found out yesterday from another poster that NAPA sells sierra pistons. Well my husband sells automotive parts, tools, and paint (not for NAPA though). He got me that hone for $17. I asked him if he sold sierra pitons he said yes, so he is going to check today how much he can get them for. Beter yet he may be able to get Wiesco (probably spelled wrong). HE gets a really good deal on some parts not so good on other parts. Like Rotors for my car are $4.00 (yes four dollars not forty) but some other things like oil he gets no discount on at all. So well see, Todays job is to see if I can get the caged bearings back in through the reed openings and greased onto the crank without them falling out. Then I need to order my intake gaskets (and if I cant get them in through the reed opening a crankcase seal (but I really really dont want to open it).

I used three different cameras yesterday (kodak, sony, and my cellphone) the problem is if I take the picture with higher megapixels I get a good picture but I am in the sticks and on dialup and the picture takes too long to load, so when I take it with a lower resolution so I can load it on here I get a poor picture.

 

[Frank Acampora]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Couple of hints on reinstalling the pistons:

I use a very large plastic zip tie to hold the rings compressed because there is not enough room for a ring compressor on the bottom cylinder.

The rods are a tight fit between the crank cheeks and you must have the piston aligned accurately or they will jam. There is more clearance on newer and merc made engines, and merc engines have captive rollers in plastic cages which makes life a lot easier. You must push the piston all the way in until the rod is flush against the crankpin and the crankpin is close to the reed opening.. Then rotate the crank slightly while you insert the bearing cages. Often the cages will jam a bit and ride over each other so you need to be patient.

Now having greased the crankpin and cages, grease each roller indiviually and with a needle nose and piece of wire, push each roller into a slot in the cage. Do them in order and rotate the cage a bit for each one. You will also need to rotate the crank slightly to make room for the rollers. Be certain that you have inserted 16 rollers and they have not popped out of position. If one does, you will need to start over. Be patient. this is a slow process and can not be hurried. The first may take an hour or longer, the others (if they cooperate) will take less time as you get the knack.

Again, using the needle nose, put on the rod cap with the bolts hand tight and rotate the crank a couple of times. You will need to put the cap in at an angle and wiggle it a bit to get it to seat. Please: before you install the pistons check each cap for its correct mating rod and the correct orientation on the rod. They are matched sets and only go one way. Now check cap alignment and if correct snug bolts to 190 inch pounds. I find a 6 inch 1/4 extension bar with a 12 point 1/4 socket adapted to 3/8 torque wrench works well.

Go on to the next piston.

 

[tater76]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Just a question to gain insight here, would it be easier just to pull the powerhead to do all this work? I am not familiar with the 4cyl Force yet, so I assume that it is a little more difficult to remove than the 2 and 3cylinder Force and Chryslers that I have pulled. I was just looking at my 85hp parts motor, and it sits so low in the cowl, looks like it would be a pain to access the bottom cylinder?

 

[pooh_b_21632]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

It looks like I can remove the lower cowl if I have to with 6-10 bolts (didnt count them) I just have to take off three electrical componets that are bolted to the cowl as well then it will slip over the top of the block (looks like it anyway). Mr. Pooh is supposed to be bringing home a bore caliper so I can make sure all the cylinders are in good shape before purchasing pistons.


NEW PROBLEM: I have been looking all day for the proper pistons, I have the 1990 version B that used the 3.375 pistons. I found the sierra pat number 18-4632 but the picture on the website had two scoops cut into the skirt of the piston and mine does not so I called Sierra tech support and was told they did not have the replacement piston for my model he gave me the OEM number of #700-819690A1 which I was unable to find either and suggested I call wiesco. Called Wiesco and the guy at tech support said its probably the 3151PS but could not tell me for sure said he would call me back that was 3 hours ago. Found a Pro-V 5100V but cant find a picture of it. Tired of looking........will try again tomorrow

 

[pooh_b_21632]

Re: Weighing options 4 new pistons and rings, to hone or not to hone, suggestions, id

Just wanted to add an update for anyone searching the forums looking for answers as I was doing before posting. I found several post that were on the right track for me but no one ever posted a fix so I figured I would be nice.

Yes the Wiseco 3151PS Pistons were the correct ones for my 1990 Version B Force 120 engine. Cheapest Place to purchase them at the time I bought mine was http://www.boatpartstore.com/forcese...al=38&val=119# s piston, rings, pin, and circlips for 1 cylinder was $84.79

Helpful hint pay someone with a hydraulic press to press your pistons off for you I recieved my pistons some time ago and it took about three weeks to finally get the rods out of the old pistons. I tried hammering them out (several times), I made a piston puller, I tried a vise, and I bought a 6 ton bottle jack press from Harbor freight which my husband proceeded to break, then a friend with a repair shop tried his 12 ton bottle jack press with no luck, another friend had a air driven hydraulic jack and had less trouble and got them all four off in a short amount of time.

Once I finally got the rods off and the new pistons on (BTW use a silver permanent marker to mark on the rod which way is up before pressing the old pistons off) I started trying to put it back together. I tried putting the bearings onto the crank first then putting the piston and the cap in I tried for some time but every time I would get the bearings on then put the piston in the bearings would slide on top of one another and after a while I broke one of the cages (they are expensive). Finally I figured it out. I took ATP-201 transmission assembly lube blue and put it onto the rod, put the bearing cage onto the rod and put the bearings into the slots. I gooped it pretty good so it would stay put. I bought a ring compressor from Pep-boys for $8 bucks and compressed the rings, centered the crank and gently pushed the piston into the cylinder so it hooked onto the crank. Then I slid the rod cap in through the reed openings with the bearing cage and bearings gooped onto it as well lined it up and pushed it forward gently with a screwdriver. I used a 1/4 inch ratchet with a long extension and a 1/4 inch 12pt socket and a swivel to put the bolts in. The swivel is essential to getting a good tight fit I did it several times without the swivel and the rod was still loose and I had to take it apart fix the bearings and start over. So save yourself the trouble and use the swivel. I torqued them all to 190 (check twice just to be sure). Once I got them all seated I spun the engine by hand about two dozen times to get them good and seated and check the torque again just to be sure they were all tight.

Hope this helps someone, Good Luck!