Need Pistons Force 120hp 1995 or Newer??

[partsgooroo]

I have a force 120 hp outboard and I need piston kits. The dealer tells me the pistons are different from 1995 and 96-up. This id what I have found out.
The piston pins are held in with snap-rings so the Clymer manual says that 95 or newer. I have found a casting number under the electrical in the starboard side.
It's 800-818154-05. There is a casting number by the cylinder head on the block 8865825. Also the fuel pump has a number on it of 98766-C1.
The dealer can't do anything with these numbers??
What is my next step??
Thanks Darryl Q.

 

[Jiggz]

It is really very hard to ID engine year and model just with casting numbers. In your case, since it falls between two different year models the only sure way to find out is to ID the parts you are looking for base on drawings at boats dot net. I took a look on the difference on the pistons between '95 and '96. According to the manual, the 96 and newer models uses the top guided rod or connecting rod. Your mention of the circ clips for the piston wrist is identical in both models. What is different is the piston, needle bearings (wrist pin), conn rod and the wrist spacers or thrusts washers. The '95 uses the old style thick wrist pin spacers while the 96 uses the thinner one.

Since you have a better view of the parts you need, I suggest you make the comparisons with what you have to that shown at boats dot net. If you are still unsure, try ordering at least the spacers (95) or the thrust washer (96) and compare to what you have. But if you look closely on the exploded drawings the difference is very obvious. I have the 89-125 and I can tell the spacers are the same as those of the 95 and older model 120's.

 

[pnwboat]

You need to measure the cylinder bores. That way there is no doubt as to what size pistons you need.

There are two sizes of cylinder bores. Small bore which is 3.312" std. size, and large bore 3.375" std. size. 1995ish they used both sizes depending on the block. You also never know what a previous owner may have done. Taking a guess or going by manuals or what someone says, will increase the likely hood that you may get the wrong ones. At $80 - $100 a piston (depending on what type you get), that can be an expensive mistake.

I've learned the hard way. Now I take the bare block to the machine shop and let them measure the cylinders and tell me what size pistons I need. They can tell you if you need oversize pistons and what oversize to get. .010, .020, or .030 oversize.

You can't depend on whether or not it has snap rings holding in the piston pins. For example, the after market Wiesco forged pistons have snap rings for all piston pins and all years for the Force 120HP motors. If it's any consolation, the fact that it does have floating piston pins (snap rings), means that it really easy to change the pistons.

 

[Jiggz]

No Title

Here's a pic of the wrist pin bearing spacers on 95 and older. Compare to what you have and if yours don't look any closer like these ones, then you most likely have a 96 and newer model.

 

[Jiggz]

Dupe

 

[Jiggz]

No Title

Test for pics

 

[Jiggz]

No Title

test for pic

 

[Jiggz]

No Title

 

[Jiggz]

No Title

 

[Jiggz]

Well it looks like despite the error message the pics are loading. Oh yes nothing like an updated forum!!!

 

[partsgooroo]

Awasm info!! Thank you very much!!
Darryl Q.

 

[Frank Acampora]

While Mercury did use the same sized pistons (3.375 bore) for years later than 1996, they also did change the pistons and connecting rods: Connecting rods were made longer, wrist pin diameter was increased, wrist pin holes were moved up in the piston wall, wrist pins were held by circlips, and both bearings in the con-rods were made larger. Incidentally, these changes along with Mercury ignition significantly increased engine performance.

THUS: best if you pull out one piston and measure it. Wiseco does make both styles of piston and it is possible to order the incorrect part.