Force 150 Piston

[Coolbreeze135]

The number 1 Piston on my Force 150 is dead no compression. It was over revved after the throttle stuck wide open on the hose(long story).

After taking the head off it is clear that it basically melted the piston, did not seize the engine. The other cylinders seem fine and tested ok on compression. I was even able to restart the motor later.

My question is can I change number 1 with the engine on the boat ? I am assuming all the carbs need to come and the engine split.. If it is possible is there anything I need to watch for when removing it?

Regards
Mark

 

[Frank Acampora]

Re: Force 150 Piston

Just as with the 3 and 4 cylinder engines, It is possible to replace one piston without disassembling the engine. This assumes that the cylinder itself has not been damaged or scored. Any damage to the cylinder will result in lower performance and less than satisfactory results.

The top carb and manifold need to be removed so you can access the big end of the con-rod, remove the cap screws, and the piston can be pushed out the head end of the block.

 

[Coolbreeze135]

Re: Force 150 Piston

Thanks Frank.
I did remove the top carb. and what I think is the manifold (the v shaped reed) I was also able to remove the rod end cap and a few of the needle bearings fell out (got em). Is this as far as it needs to come apart seems pretty tight. Looks like not room to push that piston out.

See Pic

 

[Frank Acampora]

Re: Force 150 Piston

Get in there with a long wooden dowel and push on the rod big end. The piston will push out. The difficult part is getting the new one back in and replacing the rollers and rod cap.

I never worked on a 150 so I don't know if the pistons are press fit wrist pins or clip located. If press fit you need a relatively large press to push them out. If you buy a Wiseco piston, it has circlip retained wristpin so you will not need to press in the existing wrist pin.

 

[Coolbreeze135]

Re: Force 150 Piston

Got the piston out WOW was it wasted one whole side gone.. Good news is the cylinder looked fine a little left over aluminum inside stuck to the cylinder but otherwise no gouges and it looked better than I expected. But wow I cant even imagine how im going to put all those little needle bearings back in that clip though that little hole w/o them all falling out any tips on that one

 

[Frank Acampora]

Re: Force 150 Piston

GREASE! Hint: Some OMC engines used the same sized crankpins and the rollers were retained in the cages. I don't remember which though so you would need to do the homework.

Couple of months ago someone on this forum said he used them on his Force rebuild.

 

[Coolbreeze135]

Re: Force 150 Piston

Yeah seems like I saw that somewhere looks like some real brain surgery coming up...