1990 Force 120 Cylinder Bore HELP !

[fishhead62]

I have a 1990 Force 120 . I bought the motor and didn't do a compression check. The motor ran and shifted o.k. so I thought it was fine. Not knowing about doing a compression check, I found out the hard way . One piston had 0 compression. The others were fairly high140. I disassembled the motor and found the bottom piston had a hole right through it, and the cylinder walls were scored. The problem i am having with is the size of the bore on the pistons that are already in the block. Stock pistons I have found out came in two sizes 3.312 and 3.375. the cylinder walls measure 3.354 .That's more than .040 over stock 3.312 and under .020 stock 3.375. Dilemma. I was going to hone or bore out the cylinders , but after measuring them i am not sure what to think of what I found.
If I bore it .030 over the current measurement to 3.375 am I actually boring .063 over the stock 3.312. The 3.375 stock size .010 over is 3.385 and are available . Are there sleeves available to have pressed in or am I looking at the Numbers wrong. Any help with this would be greatly appreciated.

 

[Frank Acampora]

Re: 1990 Force 120 Cylinder Bore HELP !

The 1990 120 was 3.3125 stock. The largest over size piston is .040 and you are already over that. You can NOT bore to 3.375 as the sleeve wall will be too thin. The engines did use different sleeves. Your options are:

1. Buy a new (used) block-- probably the best option now.
2. Have the block re-sleeved. about 2-300 bucks and only special machine shops have the skill to do it properly
3. Buy a NEW new block for around 1200 bucks.
4. See my private message to you edit--can't do it. Send a private message to me. Click on my name and then click on send PM

 

[thompy]

Re: 1990 Force 120 Cylinder Bore HELP !

Frank what is the tolerance for the bore, is .002 to far gone if it already had .040 pistons, not that was the case, he didn't say what was in it , maybe the hole took it out, just curious, sounds like that carb leaned out with gunk

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

I didn't know what the bore was before I took it apart. I was hoping to Bore it out 30 over and get new pistons for it but looks like thats not happening. Another question that I have would be . if its at 40 over , could I buy new 40 over pistons. You mentioned that it might be in the tolerances. Just wondering if thats an option. Not sure if that would be recommended.

 

[thompy]

Re: 1990 Force 120 Cylinder Bore HELP !

i dont know what the tolerances are,no manual, have you pulled it apart, to see what the other pistons are, they stamp them on the top, but i hear some times people will run an oversize just in one hole, im kind of new to outboards, atleast since the 80's

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

Theres only the letter A stamped on the top of them. not sure what that means. i thought they were stamped with the size . STD. etc... I thought they were like a car engine. Not so. I was told you can run an oversize piston in just one cylinder. and its ok. Dont quote me on that , its what I have ben told researching my project. Thanks for the help.

 

[robert graham]

Re: 1990 Force 120 Cylinder Bore HELP !

You could spend 1 or 2 thousand$$ and still have a 20 year old motor. Maybe find a good used motor and just kiss that old one good-bye. Good Luck!

 

[Frank Acampora]

Re: 1990 Force 120 Cylinder Bore HELP !

I know that it is difficult and you really don't want to hear that you have no options with that block, but that is the way it is! You may not appreciate my previous answer but again, those are the ONLY options you have.

You are already .002 over an .040 overbore of 3.3125 and a simple honing will not clean it. Even so, even though .040 pistons are available, old Chrysler manuals recommend not to bore more than .030 because of wall thickness. AND contrary to a number of manufacturers, total wear tolerance on these engines IS only .002

SO: AGAIN -- Unless you re-sleeve that cylinder you are skunked. Read my options in my last answer.

I do have a 1990 something block with a 3.375 bore that all your components would fit, however, you would need to buy four pistons for that one. If you are interested, send me a private message. For some reason, I can not send one to you.

Of course, you could always take out the bad piston and run the damn thing as a three cylinder 90---LOL.

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

Thanks for your help. I managed to track down a 1990 120 hp powerhead with great compression in all 4 cylinders. 133-135. I didnt really think that putting 40 over pistons would work , but I wanted it to run again. , now it will . This is a great site.

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

O.K. Here we go again. Before I actually BUY this Powerhead . There is a regular Powerhead and an L drive powerhead. . Are they one and the same? A 1990 120 powerhead is a 120 powerhead or not ?

 

[Frank Acampora]

Re: 1990 Force 120 Cylinder Bore HELP !

While the L-Drive powerhead is basically the same and will indeed bolt up to your midleg, I have it from an old Chrysler mechanic who has forgotten more that I will ever know that the L-drive crank is balanced differently.

 

[pnwboat]

Re: 1990 Force 120 Cylinder Bore HELP !

You have to be careful with the L-Drive power heads. Some of the L-Drive power heads have 13 spline crankshafts. This is where the driven shaft from the lower end connects. Most of the lower ends on the regular 120 HP motors are 15 splines.

Either way, make sure the male splines on the drive shaft match the female splines on the crank shaft.

 

[tisa]

Re: 1990 Force 120 Cylinder Bore HELP !

Hi,I have 1998 block & pistons with rods About 40 hours on it.Give me phone # if You interested.Thanks

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

Bought a Force 120 Powerhead. Hooked it up today. Got about 80 % done before I ran out of daylight. Actually fired the motor and it ran for about 4 seconds. A good sign . Need to hook up the throttle and shift levers. and little odds and ends but pretty much done. Im a happy fisherman / boater today. Thanks for all the help.
I got this Powerhead from a man in Mass. Not from a solicitation on this Forum. I wanted to post other questions about other outboards I have but I think I have been stopped from doing so. ???

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

Wait not so fast. Hooked everything up. Double checked everything , making sure all is tight . Went to start it with a fuel line and muffs on it and turned the key... Nothing. The wires got VERY hot. Not sure what to do now. Took the starter off . Checked the brushes and windings. There was a broken wire to the brush. Soldered it back on , just to see if it would crank again. In the meantime i will get a rebuild kit for it. but now I'm not sure about the wiring to the solenoid. would appreciate any help with the wiring. Seloc doesn't show a good view of it . Actually checked the schematics for it and I had it wired wrong. Will hook it up the correct way and try this again. Hopefully this wil work.

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

Got the wiring straightened out. The engine chugged a few times , then broke a flywheel key. Had to order a new one , waiting for it to get here to try again. So close. I hope.

 

[fishhead62]

Re: 1990 Force 120 Cylinder Bore HELP !

http://www.youtube.com/watch?v=pZ1SATqfBiU ITS ALIVE !!!!!!