15 johnson rebuild 1992 with 1991 15 hp block???

[wheresthefish]

hi i am going to attempt rebuilding my 1992 johnson 15 hp shortshaft outboard because the motor is in good shape but the piston ring broke and scratched up the inside of the cylinder. i have a nice 1991 block that i wanted to use from my 15 hp long shaft that i use for parts. are these blocks interchangeable? does anyone know. i dont have model numbers as they wore off. but they are the standard motors of these years. any help is greatly appreciated. thanks.

 

[lexkyboater]

Re: 15 johnson rebuild 1992 with 1991 15 hp block???

See my other response to the "15 hp 1992 johnson rebuild with 1991 johnson 15 block" thread.

 

[lexkyboater]

Re: 15 johnson rebuild 1992 with 1991 15 hp block???

Hmmm - don't know where that other thread went... What I found on http://epc.brp.com/default.aspx?brands=ej&lang=e was that the part numbers for the cylinder and crankcase assy shared the same part numbers for the two years.

 

[wheresthefish]

Re: 15 johnson rebuild 1992 with 1991 15 hp block???

thanks for the reply, so they have the same part number. does that mean i can do the switch? can i also interchange the pistons? i might need to take a look at that website. when i tried eariler i couldnt view it.

also does anyone have an idea if i need a special tool to put new rings around the pistions? thanks again.

 

[CATransplant]

Re: 15 johnson rebuild 1992 with 1991 15 hp block???

If it's the same part number, it's the same part. You should be able to swap in anything that's in good shape from your old motor. For the rebuild, though, you should definitely have the factory repair manual. It's a cheap investment, and it will help you not to make mistakes that could spoil the job for you.

Replace any parts that are seriously worn or out of spec. There's no point in going through this engine and having it fail shortly after you finish. I can't give you any detailed help, but if you follow the factory repair manual to the letter and replace any parts that you should, you'll have a good engine.

One other thing: The factory manual will tell you how to check the cylinder bores on your 91 block. Do it. If they're worn too much, you'll waste your time. I'm also not sure about honing those cylinders, but the factory manual will help you with that, too.

 

[lexkyboater]

Re: 15 johnson rebuild 1992 with 1991 15 hp block???

Yeah, I concur with CATransplant - I have a seloc manual that covers 60 - 235 HP up to 1991, and it says use an inside micrometer to check if it's out of round. Anything over .003 to .004 means it has to rebored to the next available size piston. For 1989 and later, the ring end gap should be .19 to .30 my manual says. The manual also says each ring has to be checked in the cylinder. Also pay attention to taper on rings and always install taper on top. The pistons also have dowel/locating pins in the ring grooves and that's where the ring ends go to prevent the rings from rotating in the cylinder. Rings also have to be installed in the proper ring groove in the piston. They say you can use thumbnails or ring expander to install rings. The pistons can also be measured with outside micrometer, and the difference between them and inside measurement of the cylinder it's going into should be something like 0.0025 to .0075 - you need to check the manual for your specific model. You'll want that factory manual. Even my seloc manual includes detailed instructions on honing - rotate at 30 rpms, use long stones to prevent scratching ports, generous honing oil and just do it enough to deglaze cylinders to get the rings to seat.