piston to cylinder clearance for J2RCTD

[ktmdriver]

Hello all, new here and new to fixing outboards. My father wanted me to fix a siezed piston from his 1983 2hp Johnson J2RCTD. I ordered a one over piston and took the block to machine shop that normally works on my offroad bikes, but was surprised that he did not know what the piston to cylinder clearance was based on his many books.

So the question is, does any one know what is the piston to cylinder clearance for this model?

Thanks

[boats.net]

Johnson manuals don't list the piston to cylinder clearance, the manual state to add oversize dimensions to std bore(if .020 oversize piston is used add .020 to std bore).
I don't have the manual for your motor, I have back to 1991 and specs for that 2 hp is
Std bore 1.8890-1.8906 in
Std piston diameter 1.8868-1.8873 in
Piston ring end gap 0.0059-0.0138 in

[ktmdriver]

Thank you for the info. I spoke to my machine shop guy and he miced the bottom of the bore and came up with a 1.567 which he claims is not the standard bore size for that type of motor and that is why he is being thrown for a loop. According to his Johnson chart the standard bore should be four thousands less, but if thats the case and he bored it according to the chart, threre would be no clearance for the new piston. So he told me to make the call as he did not want to be responsible if the thing siezes.

I made the call and told him give it a four thousands clearance and hope the thing does not sound like it's full of marbles. I figure it's better to have it a bit loose than too tight and risk a sieze.

Aaron.

[boats.net]

You do need to find correct service manual and get the right specs, maybe someone has one and they post the specs for you.