89 85HP Force Piston Replacement

[greenoil]

I have a 1989 force 85hp. 856X9H. I bought the boat for $1500 came with all the running gear, jackets and a year of storage. My g-friend and I have taken the boat out four times. It has been a real blast. The problem is that it will only run out to 3900 rpms at WOT with 1 person. 3500 rpms WOT with a full crew and tube behind. I knew some thing was wrong with it. I replaced the water pump before I ever took it out. No problems. Decided to check the compression finally. 1-130, 2-30, 3-130. I sumized from the test that cylinder two was completely trashed.

I pulled the head off and cylinder 2 was definately trashed, err just the piston really. Luckily the cylinder still looked great. I took of the carb adapter plate and took out the reed valve on #2. I removed the rod cap with a 1/4" 12 point socket and pushed the piston and rod out with a socket extension. I collected the rod bearing and carrier and stuck them in a clean dry gatoraid bottle. We put shop rags in the cylinder (my g-friend and I) and loosely buttoned it back up.

We got to the house and ordered all the parts. 1-Wiseco piston and wristpin kit. 1- New fuel pump, 2-carb adaptor gaskets, 1-head gasket, 2-carb gaskets. I found all the torque specs:

Head Bolt=225 in/lbs, Rod bolts=185 in/lbs.

I plan on using petroleum jelly to put the rod bearings back in.

Know does anyone have any tricks or advice to help me put the Piston back in?

-Shawn-

 

[MWBROWN]

Re: 89 85HP Force Piston Replacement

Sounds like you have done a great job so far.

Did you check the cylinder for roundness? Is it still crosshatched?
Did you hone it to prepare it for the new piston and rings?

I don't think the jelly is a good idea for the bearings. On a car I would use lubriplate, but others will tell the correct stuff, it that is wrong.
I am sure you will need to get a ring compressor to put the piston back in.
Some of the auto shops rent them pretty cheap.

I just looked in my manual and it says to use needle bearing grease or multi purpose grease and also straight 2 cycle oil to lubricate.
Also said to keep everthing super clean.

Good Luck. There are others that have much more to add I am sure.

Mike

 

[Frank Acampora]

Re: 89 85HP Force Piston Replacement

You have done all that is necessary for now. You will need a press--about 6 ton to press out the original wrist pin so you can re-use the rod. The Wiseco comes with a loose wrist pin and circlips so no special tools are needed to install it. When you go to install the rod, coat the inside of the small end with grease to hold the needles. The two spacers go on either side of the rod with the small end toward the rod and the big end toward the piston. Work carefully so the pin does not dislodge the needles when you push it through. When you go to install the assembly in the block, Again, use a little grease on the rollers to keep them in place as you rotate the bearing cages. When you put on the cap, just snug the bolts then use a scribe , compass point, or pencil to run over the break point. If they pass smoothly over the break at the ground area designed for this purpose, tighten the cap bolts in about three stages--100, 130-140,- 180-190 (final). If not, tap gently with a small hammer until they are properly aligned. Double and triple check cap alignment to be sure. Note the position of the rod in the piston. There are 2 v shaped notches on one side of the big end and 2 flat notches on the other. It's not critical, but factory recommends installation with the flat notches down--look at the other two rods and match them. Use grease not petroleum jelly. I am not sure that 2 cycle oil will dissolve jelly quickly. Also, pre lube the piston, rings ,and rod with 2 cycle oil before installation. Use double oil in the gas and take it easy on the engine for a while. If you compare the oil on the old piston with fresh oil, you will see that oil that has been heated within the engine seems to have higher viscosity and lubricity. Give the engine a while to build up this protection.
Wisco pistons can be installed without a ring compressor if you do not have one. Push in lightly on the piston while using a small screwdriver to push on the ring. Start at one end at the gap and work your way around. work carefully so as to not scratch the ring surface. It may take a couple of tries, but eventually you will get it and the piston will pop right in.

Oh, by the way: The rod is a relatively snug fit between the crank cheeks. If the piston is slightly cocked or if the rod is not perfectly centered in the piston, it woll not come up to the crankpin. If this happens, wiggle it as you try to center it.

 

[MWBROWN]

Re: 89 85HP Force Piston Replacement

See, I told you someone smarter would add the correct info.

LOL

 

[greenoil]

Re: 89 85HP Force Piston Replacement

Thanks Guys. I am sure that it will work out well.

 

[greenoil]

89 85HP Force Piston Replacement

Ring End Gap Clearane
Clymer says:
1984-1989B - 0.006-0.016
1989C-1995
Top ring - 0.010 - 0.020
Bottom Ring - 0.006 - 0.016

 

[Darin300]

Re: 89 85HP Force Piston Replacement

Hey,
I have the same engine and cylinder #2 is bad also. Must be something with that engine. One question where did you get your parts from. The wiesco piston ect, and I'm assuming it's a standard bore. My local dealer here said I would have to bore it 10 over because the standard piston is not available anymore. Sounds like your doing a good job, thanks for the info.

 

[baxtr]

Re: 89 85HP Force Piston Replacement

Hey,
I have the same engine and cylinder #2 is bad also. Must be something with that engine. One question where did you get your parts from. The wiesco piston ect, and I'm assuming it's a standard bore. My local dealer here said I would have to bore it 10 over because the standard piston is not available anymore. Sounds like your doing a good job, thanks for the info.

http://www.outboardparts.com/chrysler/mall/forcepistons.htm

 

[greenoil]

Re: 89 85HP Force Piston Replacement

I bought gaskets and such from iboats because of their awsome forum. The piston came from wiseco. I have always liked wiseco. I didnt bother measuring the cylinder bore just replacing it with a standerd to try to get a little more time out of the engine for the season. Not a great practice but hey do what you have to do to pull the tube.
Shawn

 

[greenoil]

Re: 89 85HP Force Piston Replacement

Wow, that new piston really ramped up the power. My boat is running great. I did a little work on the power trim. ie. tighten the bolts that hold the engine to the transom. Boat is still not quite running in the middle of the power band should have that fixed soon. Also the ring end gap clearance was right on and have equal compression accross cylinders. Heck Yeah!

 

[Frank Acampora]

Re: 89 85HP Force Piston Replacement

Now, put a small disposable auto gas filter after the fuel pump and before the carbs. Check all three of your carbs to be sure the inlet needles are not clogged. If the center is, and it runs lean, you will melt the new piston. Better safe than sorry.