1994 40 HP Force, Blown Lower Piston

[northof48]

Hello out there, after researching and reading through hundreds of posts on this site I finally decided to join so I can try to learn a little more about this engine.
I recently purchased a 16 ft legend from my neighbour with a 1994 40 HP force on it. Originally I was trying to help him out by taking a look at it for him. After trying all the tricks and hoping it was just a stuck ring I finally popped of the the head cover off and found the bottom piston had damage on the top of it. I noticed some minor markings on the bottom of the cylinder wall and do not want to pull the power head of and get it bored out, without seeing a picture I know it is hard to reccomend what I should do. In this case with it only being a two cylinder should I replace both pistons or can I get away with only replacing the one?

As I live in Ontario, I can not get OEM parts for this outboard and will have to rely on getting them from E-Bay, has anyone had any dealings with parts from E-Bay and any recomendations would be appreciated.
I have already wrote off getting this motor up and running this year and after pricing out how much a new motor would cost me, I have decided to take a crack at it over the winter and see if I can rebuild it. I have read on some of the other posts that the pistons can be removed without taking the powerhead off, is this possible to do with the 40 HP and if so is it the same way as described in the other posts of the same subject?
Any help on this would be greatly appreciated as I would like to try and save alot of money and get this motor up and running again.

 

[Jiggz]

Re: 1994 40 HP Force, Blown Lower Piston

You might not get the OEM but actually you can get Wiseco piston kits which I personally find to be better than OEM. They are still available. Search for Seiler Marine. Read thoroughly as you will need a bearing kit for the piston pins to use Wiseco. As for changing both, there is no need unless you just feel like having money, time and energy to burn. Just make sure you prepare the cylinder first and at least take a bore gauge measurement before ordering.

 

[jerryjerry05]

Re: 1994 40 HP Force, Blown Lower Piston

Depending on the damage???
IF??? You can feel any scoring at all in the cylinder wall????
It needs to be bored over sized.
Putting new rings in a scored hole is not good.
Might last for a while? Might not.
They figure out what caused the piston to go bad?
Wisco is a good piston. The other piston can't use their rings.
Yes you can do the job without pulling the head.
I just like doing the job right.Not saying it's wrong to do it that way,just don't like it.

 

[northof48]

Re: 1994 40 HP Force, Blown Lower Piston

Thanks for the replies, as for the damage there is a small goove in the bottom of the blown cylinder. After looking at it, it probably should get bored out oversized. The only worry I have is that I have never had to take the power head off of an outboard and am not completley sure on the procedure. What would be the best manual to get that will show me step by step instructions on how to go about it. By looking at the cowling I am going to have to take them off in order for me to get to the bolts that are holding the powerhead assemblie on...right???

This could get very interesting I just hope that im not diving off the deep end on this one.....

 

[Anchor Marine Repair LLC]

Re: 1994 40 HP Force, Blown Lower Piston

Thanks for the replies, as for the damage there is a small goove in the bottom of the blown cylinder. After looking at it, it probably should get bored out oversized. The only worry I have is that I have never had to take the power head off of an outboard and am not completley sure on the procedure. What would be the best manual to get that will show me step by step instructions on how to go about it. By looking at the cowling I am going to have to take them off in order for me to get to the bolts that are holding the powerhead assemblie on...right???

This could get very interesting I just hope that im not diving off the deep end on this one.....

You can get a Clymer or Seloc manual for about $40.. I'd buy one, then read the sections that will apply to you. Pulling the powerhead is easy, yet only the beginning. So if it looks too daunting, then it is.

You will really need a foot pounds torque wrench, and an inch pounds torque wrench.

If you go that far into it, bore them both. This motor is 19 years old; the other piston is going to have wear. If you don't, the non replaced piston will be your next problem.

I think if you have all the needed tools, and the time to do it by the book, you'll be fine.

 

[northof48]

Re: 1994 40 HP Force, Blown Lower Piston

Hey guys, thanks for the help, just.thought i would update and maybe get your opinions on my options. I have removed the powerhead and after a trip to the neighbours house and a few pops we managed to male a puller for the flywheel. (Will post pictures for future reference for.others) I have it all seperated and brought it to.a machine shop. Here is where I am stuck making a.decision...He honed it out and the top cylinder is fine but.the bottom cylinder will have to.be bored out at least .020 over. Now if I am getting the one cylinder done is.it neccessary to get them both.done or just best practise. I am waiting to order the pistons untill I find out how I should proceed. your input would be greatly appreciated, thank you.

 

[Anchor Marine Repair LLC]

Re: 1994 40 HP Force, Blown Lower Piston

Hey guys, thanks for the help, just.thought i would update and maybe get your opinions on my options. I have removed the powerhead and after a trip to the neighbours house and a few pops we managed to male a puller for the flywheel. (Will post pictures for future reference for.others) I have it all seperated and brought it to.a machine shop. Here is where I am stuck making a.decision...He honed it out and the top cylinder is fine but.the bottom cylinder will have to.be bored out at least .020 over. Now if I am getting the one cylinder done is.it neccessary to get them both.done or just best practise. I am waiting to order the pistons untill I find out how I should proceed. your input would be greatly appreciated, thank you.

Never ever hone a 2 stroke cylinder, and try to make it run on a standard sized piston. Piston to cylinder wall clearance on a new motor or rebuild is .005" So if you hone out a cylinder that is 19 years old, the clearance in going to be out of spec in a hurry.

Honing removes metal. You can already see how well a piston works via#2 when metal is removed.

Since you're that far in, put in 2 new .020 oversized pistons, with freshed BORED .020 cylinders. Wiseco's are the best for this application.

I'd hate to see you back up on this board in a few months trying to figure out why #1 isn't carrying it's half of the load.

 

[jerryjerry05]

Re: 1994 40 HP Force, Blown Lower Piston

There are thousands of rebuilt motors out there with an over sized and a honed out cylinders.
You need to trust the machine shop. They should be able to tell you if the second cylinder need to be over sized.
EVERY motor I've rebuilt has usually 1 bored out cylinder and 2-3 honed out cylinders.
So far none have come back.
You can do both cylinders. I'm just saying it's not necessary.