1995 Force 120 Compression issue

[MBLarry]

I have a 1995 Force 120 with low compression on one cylinder (30PSI). The other cylinders are running between 90 and 100 PSI. Does anyone know if the rings can be changed with removing the Powerhead? I just changed the head gasket and all of the cylinders are clean with no scratches so I don't think I need to have the block machined. Any advice is greatly appreciated. Thanks

 

[roscoe]

Yes you should be able to change out pistons by removing head and fuel intake to give you enough access, unless you have huge King Kong hands.

 

[jerryjerry05]

You neglected to say what cyl. is low???
If it's one of the top 3???
Then you could probably fix it without removing the power head.
The bottom cyl. is pretty hard to get at for fixing and replacing the rings.
The bearings are loose and need to be stuck in place with a special grease(bearing assy .grease)
On the bottom cyl. it can be hard to get them in place.

 

[MBLarry]

Thanks Jerry. Bad cylinder is #1 (30PSI), Cylinders 2 & 3 are (100PSI), #4 is (90PSI). Do you think that using standard rings will be OK? Cylinders are nice and clean. Do you think it would be a good idea to put new rings on all the cylinders or just #1.

 

[jerryjerry05]

The 95 compression:
As I understand they made that motor so the comp on 1 and 4 was 10# lower than #2/3

And yes if the others are all ok just re-ring #1
And you will have to use standard rings, trying to squeeze in oversized rings won't work and would probably screw up and need to be redone if you managed to get them in??

 

[MBLarry]

Thanks Jerry. I'm still trying to separate the block. Gonna give it another try today so I can pull #1 piston to see what shape it's in. Thanks for the help. Have a great day.

 

[jerryjerry05]

Make sure the bolts are out, they used to hide one on the older models.
Then the sillycone is the only thing holding it.
Be careful when prying the pieces apart. and don't damage any mating surfaces.

 

[MBLarry]

OK. All the bolts are out but the block wont separate. Seems like something is holding the bottom . Does anyone know if there are bolts on the bottom of the powerhead, which would mean that the powerhead must be removed before I can split the block.

 

[Nordin]

You can not split the cylinderhead and crankcase without pulling the powerhead of the leg/midsection.

To replace a piston without pulling the powerhead, you must do as roscoe mention.
Pull the head and remove the carbs and intake manifold.

Then you are able to.remove the piston rod from the cramkshaft through the intake.
This is a trickey way but it can be done.

To dismantle is easy, but you have to be careful not losing needles.
The should be 16 at each rod.

To reassemble is way more difficult, but it can be done.

 

[jerryjerry05]

Yank it!!
Remove the adaptor plate.

Find a parts diagram and look at the connecting pieces.

This site has some parts but the images for them aren't there.
boatsdotnet has better parts diagrams.

 

[MBLarry]

Thanks for all the advice everyone. Looks like I am going to have to pull the powerhead. Got all the bolts out that hold the powerhead to the bottom leg but the powerhead won't budge. Luckily the local boat shop near me said he would pull the powerhead off the boat for me sometime next week. Then I can do the rebuild the right way with the powerhead on the work bench. Thanks again for all the help.

 

[jerryjerry05]

Keep us posted.

Remember to take a LOT of pics as you work.
There are a bunch of different size screws so label and separate.

 

[MBLarry]

I found out why the power head won't come off. Located 2 5/16" hex bolts under the rear section. Problem is, I can't to them with a hex wrench, not enough clearance and they are pretty rusted. If I need to remove the power head I guess my only option is to drill these hex bolts out. Has anyone done this before?
I am going to try and remove #1 piston by unbolting the bearing cap through the intake like Nordin suggested. My only concern is that if I lose any bearings, the power head will have to come out. I am assuming I can remove the bearing cap through the intake side and push the piston out the front. Not much room to work in. Any suggestions to make this go a little easier?

 

[jerryjerry05]

If you drop a bearing it shouldn't be hard to retrieve.
The assy. grease holds them in place as you reassemble.

Use the search function, a member FrankA (RIP)had a few repairs on replacing the piston without a total teardown.

 

[MBLarry]

Thanks for the help Jerry. I got the piston out and retrieved all 16 bearings. Found the broken ring. Piston is pretty scarred near the top and has distorted the ring race. I think I'll just go head and replace the piston. Any suggestions on who might sell a complete piston already assembled. I know there are plenty suppliers but I would rather trust someone who has done this before to get a quality product. You were right, it wasn't that hard. My confidence has been restored. Now all I have to do is replace the piston and put everything back together. Glad I didn't have to remove the power head. Thanks again.

 

[Nordin]

Good to hear you got it apart.

It will be a lot harder to reassemble but it can be done.

I suggest you to use Wiseco aftermarket pistons.
It has the needle for the piston pin in the rod not in the piston.
Much easier to assemble, but you have to buy the wrist pin kit too, not only the piston.

There are other piston brands that are cheaper then Wiseco but I have no experience of them.
If you want to use OEM pistons check with Franz Marine because I know he has OEM pistons for same price as Wiseco.
Do not know if he has the 3,375 in for same price but he has the 3,312 in.

Know this because I am in oder to buy pistons from him for a Chrysler 75Hp 1975.

 

[MBLarry]

Thanks for the help Nordin. I did order the Wiseco piston and wrist pin kit on Amazon. They were a little cheaper than ProMarine. Now, putting it back together will be a lot of fun. Hope I can remember where went. Thanks again for the help.

 

[jerryjerry05]

One tip: the rings for the Wiseco Pistons will only fit Wiseco.
Other rings won't work on them.